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                 U.S. DEPARTAENT OF THE INTERIOR

                         NATIONAL. BIOLOGICAL SERVICE




                                                                        BIOL 0 GICA L SCIENCE REPORT 3




                                                 Or                     HABITAT               SUITABILITY
                                                                        IND'EX          MODELS:
                                                                       -NON-MIG,RATO,RY
                                                                        FRESHWATER.                    LfFE""'"
                                                                        STAGES,OF
                                                                        ATLANTIC                SALMON

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                              /0001





               U.S. DEPARTMENT OF THE INTERIOR

                      NATIONAL BIOLOGICAL SERVICE
                         WASHINGTON, D.C. 20240



                                                               BIOLOGICAL SCIENCE REPORT 3
                                                               MAY 1995






                                                               HABITAT SUITABILITY
                                                               INDEX MODELS:
                                                               NONMIGRATORY
                                                               FRESHWATER LIFE
                                                               STAGES OF
                                                               ATLANTIC SALMON



                                                               By



                                                               Jon G. Stanley

                                                               and

                                                               Joan G. Trial




                        LIBRARY
                      NOAA/CCEH
                   1990 HOBSON AVE.
                 CliAS. SC 29408-2623







                                                                      Preface


                       Information in this report is for impact assessment and habitat management. This Habitat Suitability Index
                    (HSI) model for nonmigratory freshwater stages of Atlantic salmon is the third generation of a model that was
                    developed originally from a review and synthesis of existing information on Atlantic salmon (Trial and Stanley
                    1984). We define a juvenile as either the fry or parr stage up to the time of transformation to the smolt. We
                    also include model variables for the embryo stage. We report on how the model was modified based on field
                    testing in Maine in 1984 and further evaluated by comparison of alternative model outputs with a long-term
                    data base from Canada and habitat selection data gathered in Maine. Despite the testing that went into
                    developing this HSI model, it is nevertheless a hypothesis of species-habitat interactions, not a statement of
                    proven cause and effect. These interactions are presented as an index on a scale from 0 (unsuitable habitat) to
                    I (optimally suitable habitat). Through further use of this HSI model in assessing habitat in relation to Atlantic
                    salmon populations, this index can be further refined. The National Biological Service encourages model users
                    to convey comments and suggestions that may help increase the utility and effectiveness of the model. A form
                    is provided in the appendix for this purpose.








                                                                            Contents

                                                                                                                                                Page
                     Preface   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    ii

                     Abstract    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    I
                     Habitat Use Information For Atlantic Salmon         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    I
                         General   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    I
                         Age, Growth, and Food       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
                         Reproduction    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
                         Specific Habitat Requirements     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    3
                     Habitat Suitability Index (HSI) Models      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    6
                         Applicability of the Models     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    6
                         Model Description     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    8
                         Suitability Index Graphs for Model Variables      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    8
                         Rationale and Assumptions for Suitability Indices (SI's)      . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13
                         Field Application of the Models     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  13
                         Interpreting Model Outputs      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
                         Sources of Additional Models      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
                     Acknowledgments       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .  15
                     Cited References      . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
                     Appendix. Model Evaluation Form         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  18









                        Habitat Suitability Index Models: Nonmigratory Freshwater Life
                                                               Stages of Atlantic Salmon


                                                                                        by



                                                                                Jon G. Stanley

                                                                         National Biological Service
                                                                         Great Lakes Science Center
                                                                               1451 Green Road
                                                                        Ann Arbor, Michigan 48105



                                                                                        and



                                                                                 Joan G. Trial


                                                           Maine Department of Inland Fisheries and Wildlife
                                                                              Fisheries Division
                                                                                650 State Street
                                                                            Bangor, Maine 04401



                                     Abstract.     A Habitat Suitability Index model was developed by evaluating individual suitability
                                     indices of 17 environmental variables that have been shown to affect productivity or survival of
                                     nonmigratory freshwater life history stages of Atlantic salmon (SaInto salar L.). These stages included
                                     egg, embryo, fry, and parr but not smolt. During summer base flows, the most suitable habitats had
                                     temperatures of 16-191 C, oxygen percent saturation exceeding 60%, and pH between 5.5 and 6.8.
                                     The most suitable current velocity was 10-30 cm/s for fry and 10-40 cm/s for parr. The most suitable
                                     depth was 10-40 cm for fry and 20-50 cm for parr. The Habitat Suitability Index model is useful for
                                     evaluating stream habitat for production and survival of juvenile Atlantic salmon when these variables
                                     cannot practically be measured directly.

                                     Keywords: Atlantic salmon, ecology, habitat, water quality, substrate, streams, parr, spawning, habitat
                                         suitability index.


                         Habitat Use Information For                                       Europe it ranges from Iceland to Portugal, including the
                                      Atlantic Salmon                                      Baltic Sea (Netboy 1974). Anadromous populations once
                                                                                           migrated into most New England streams and the St.
                                                General                                    Lawrence River tributaries, including Lake Ontario and
                                                                                           Lake Champlain. Dams, pollution, and overfishing have
                        The Atlantic salmon, Salmo salar L., inhabits the North            eliminated spawning runs over much of the Atlantic
                     Atlantic Ocean basin from Greenland to the Connecticut                salmon's range in North America and Europe (Danie et al.
                     River of New England (Scott and Crossman 1973). In                    1984; Mills 1989; Thompson 1993). Landlocked popula-
                                                                                           fions in North America, on the other hand, were endemic to
                     'Present address: School of Natural Resources and Environment,        only a limited number of large lakes and watersheds but now
                      University of Michigan, Ann Arbor, Michigan 48109-1115.              occur in numerous lakes, especially in Maine, because of

                                                                                                                                                             I








                     2 BIOLOGICAL SCIENCE REPORT 3



                     stocking (Warner and Havey 1985). The juveniles of               30 cm/s, corresponding to the preferred habitat selected by
                     anadromous parents can be distinguished from juveniles of        parr (Heggenes and Borgstrom 1991).
                     landlocked populations, but the difference is not great             Juvenile Atlantic salmon occupy stations in streams
                     enough to categorize any particular individual (Riley et a].     and feed on invertebrates driffing on the surface and in the
                     1989). Their habitat use in small streams is similar (Sayers     water column (Bley 1987). The diet is variable, generally
                     1990), and the Habitat Suitability Index (HSI) model in this     consisting of the larvae of mayflies, chironomids, caddis-
                     report applies to both.                                          flies, blackflies, and stoneflies; annelids; and mollusks
                       The Atlantic salmon has high social and economic               (Scott and Crossman 1973). Larger juveniles also eat the
                     value. The adults are harvested commercially on their            adult fortris of aquatic insects and terrestrial insects. Food
                     feeding grounds off Greenland and southern Labrador,             size varies in direct proportion to the size of the fish
                     Canada, and they are caught in the recreational fishery          (Sosiak et at. 1979). Atlantic salmon are opportunistic
                     during their migration as they reenter fresh water. The          feeders, readily changing their diet to the most abundant
                     annual return of anadromous Atlantic salmon to U.S.              prey available.
                     streams is about 5,000 individuals; the number returning            After juveniles reach a total length of 125-150 mm,
                     from year-to-year varies about five-fold (Rideout 1989).         environmental stimuli trigger transformation into a smolt
                     In Canada, the annual production potential is about 1.5          ready to migrate to sea (Danie et al. 1984). At the smolt
                     million large salmon and an equal number of grilse, which        stage, landlocked salmon migrate from streams into lakes
                     are young salmon that are returning to their native rivers       (Warner and Havey 1985). Migration is keyed to environ-
                     to spawn after one winter at sea (Lear 1993).                    mental stimuli of rising water temperature, freshets, and
                       Worldwide there are more than 350 recognized stocks            photoperiod (Bley 1987). A few individuals in one popu-
                     of Atlantic salmon (Chadwick 1985). In general, each             lation of landlocked Atlantic salmon migrated to lakes in
                     major river system has its own stock uniquely adapted to         autumn (Warner and Havey 1985).
                     the local conditions (Thorpe 1988). In North America, the                             Reproduction
                     populations of Atlantic salmon are bolstered by stocking
                     of hatchery fish (Rideout 1989). In some runs, more than             Atlantic salmon spawn in fresh water during October
                     90% of the fish are from hatcheries. The juveniles are           and November when water temperatures reach 4.4-5.6* C
                     generally stocked when they are 1-year-old smolts ready          (DeCola 1970). Eggs are deposited in redds dug by adult
                     to migrate to the sea. In the United States, the hatchery        females at the downstream end of riffles where water
                     stock consists of seven different strains or developing          percolates through the gravel or at upwellings of ground
                     strains reared at six federal and four state hatcheries (Kane    water. One or more males fertilizes the eggs as they are
                     1989). The HSI model was developed for the stock of              deposited, and the female then completes the redd by
                     Atlantic salmon inhabiting streams in New England and            covering the eggs with 10-25 cm of gravel displaced from
                     the southern Canadian maritimes. Suitability indices (SI's)      upstream. The eggs are slightly adhesive and stick to the
                     have been produced for Atlantic salmon in Newfoundland           substrate until they are covered.
                     (Scruton and Gibson 1993), and a workshop to develop                The eggs incubate over winter buried in gravel. The
                     models was conducted in 1992.                                    incubation period varies with temperature. Eggs hatch
                                                                                      after 175-195 days under normal winter conditions of
                                 Age, Growth, and Food                                Maine (Jordon and Beland 198 1). The incubation time of
                                                                                      110 days cited by Leim and Scott (1966) was for a tem-
                       Juvenile Atlantic salmon grow relatively slowly in             perature of 3.9' C, typical of a hatchery drawing hypolim-
                     fresh water, whereas adults grow rapidly at sea. Juveniles       nionic water from a lake.
                     may spend 2-3 years in fresh water to reach 125-150 min             After hatching, the eleutheroembryos (alevin or yolk-
                     length in New England and 4-8 years to reach 180 mm in           sac larvae) remain buried in the gravel for about 6 weeks,
                     Ungava Bay, Canada (Schaffer and Elson 1975). The                until their yolk sac is depleted of nourishment. The resul-
                     young salmon grow fastest at temperatures of 15-190 C            tant fry begin foraging while still in the substrate, then
                     (DeCola 1970). The lower temperature limit of growth,            emerge at night from mid to late May in Maine (Gustaf-
                     which varies with nursery stream conditions, ranges from         son-Marjanen 1982) and from late May to early June in
                     5 to 10' C (Jensen and Johnsen 1996). Survival is POsi-          Canada (Scott and Crossman 1973; Lear 1993). In one
                     tively correlated with water discharge from streams              river in Finland, emergence was as late as July (Mills
                     (Frenette et al. 1984; Gibson et al. 1993). Growth in fresh      1989). Survival from fertilization through hatching was
                     water also is limited by availability of food, interspecific     74%, and only 2% from fertilization through emergence
                     and intraspecific competition, and a range of other factors.     (MacKenzie and Moring 1988). Chadwick (1982) found
                     Growth is fastest in habitat with water velocities of about      that the survival rate was depressed during a year when







                                         RABrrAT SurrABiLrry INDEX MODELS: NONMIGRATORY FRESHWATER LiFE STAGES OF ATLANTic SALMON 3



                    winter air temperatures and water discharge were both              for first-year and yearling parr demonstrate that Atlantic
                    low. After emergence, fry disperse, mostly downstream,             salmon have the highest temperature limits for feeding
                    and establish territories, Dispersal is highest at night (Crisp    (22.5' C) and survival (27.8' C) among brook trout
                    1991).                                                             (Salvelinusfontinalis), brown trout (Salmo trutta), and five
                                                                                       species of Pacific salmon (Elliott 1991).
                            Specific Habitat Requirements                                 The information on temperature relationships from the
                                                                                       literature was adequate for creating SI's for spawning
                       During its anadromous life cycle, the Atlantic salmon           temperatures, egg incubation, upper tolerances, and sum-
                    completely changes its habitat from freshwater streams to          mer growth. The information was inadequate for develop-
                    the sea. This report emphasizes the freshwater segment of          ing models for cold lethal temperatures.
                    the life cycle. Atlantic salmon require cold, clear streams
                    that flow freely to the ocean. Because many such streams           Dissolved Oxygen
                    in the northeastern United States and Canada arise in areas
                    with granitic bedrock, they are subject to acidification.             Oxygen concentrations near saturation are needed for
                    Atlantic salmon streams are generally well oxygenated,             optimal development and growth. Embryo and larval de-
                    except in a few rivers receiving industrial or domestic            velopment requires a minimum of 6 mg/L of dissolved
                    pollutants. Impoundments on many rivers not only block             oxygen (Elson 1975). Mortalities occur if embryos are
                    migration but also create long reaches of still water that         exposed to oxygen concentrations of less than 6-7 mg/L
                    result in increased water temperatures. The environmental          (DeCola 1970). Juvenile salmon do not occur in streams
                    requirements of Atlantic salmon were thoroughly re-                in which dissolved oxygen regularly drops below 5 mg/L
                    viewed by Gibson (1993).                                           (Elson 1975). In the laboratory at 14.5' C, Atlantic salmon
                                                                                       juveniles select the highest oxygen concentration avail-
                    Water Teinperature                                                 able-7.5 mg/L or 72% saturation (Trial and Stanley
                       Temperature is a key     variable in determining habitat        1984). At 15-160 C, lethal concentrations are 1.5 mg/L for
                    suitability for Atlantic salmon. All stages of the life cycle      juveniles during the first summer of life and 1.9 mg/L
                    require cool temperatures. Spawning occurs between 4.4             during the second year (DeCola 1970).
                    and 10' C; the optimal temperature for fertilization and              We converted all dissolved oxygen concentrations to
                    incubation is about 6' C (Danie et al. 1984). Development          units of saturation using standard tables to construct an SI
                    proceeds, but at a slower rate, at temperatures as low as          for minimum summer values.
                    -0.5' C (Peterson 1978). Incubation temperatures above             Acidity
                    12' C cause direct mortality, whereas temperatures be-
                    tween 8 and 12' C may cause secondary mortality because               The pH of salmon streams in granitic, sandy, or boggy
                    of fungal infections (Garside 1973; DeCola 1975).                  areas may be depressed by melting snow or heavy rains
                       Newly hatched larvae are exposed to and tolerate rising         that contain acid. Episodes of low pH are often accompa-
                    water temperatures in spring. Although they have little            nied by high concentrations of metal ions that ]each from
                    opportunity for selecting temperature, if given a choice           the soil, especially aluminum (Lacroix and Townsend
                    they will move to the coldest temperature available (Peter-        1987). Thus, toxicity may not be caused by acidity per se;
                    son and Metcalfe 1979). At about 250 degree-days after             nevertheless, pH may serve as a convenient indicator of
                    hatching, when the fry establish territories in streams, they      water quality. For many areas in New England and the
                    prefer a temperature of 14' C. Juveniles (13-16 cm total           Canadian maritimes, organic compounds chelate alumi-
                    length) select a temperature of 14.5' C (Trial and Stanley         num. Rivers in Nova Scotia with a mean annual pH of less
                    1984). They need a growing season of about 100 days with           than 4.7 have lost their salmon runs, in rivers with pH
                    stream temperatures above 6' C (Power 1969).                       between 4.7 and 5.0, runs declined, and in those with pH
                       The optimal water temperature for growth and produc-            above 5.0, runs were normal (Watt et al. 1983). In these
                    tion-] 5 to 19' C (DeCola 1970)-seems to be slightly               same streams, juveniles were most numerous where the
                    higher than the preferred temperature. Growth seemed to            mean annual pH was above 5.4, were much reduced be-
                    be fastest at 16.6' C (Siginevich 1967). In the laboratory,        tween pH 4.7 and 5.0, and were absent below pH 4.7.
                    p4rr grew better at 13-19' C than at colder temperat      Iures       Eggs develop normally at pH 6.7 (Peterson et al. 1980).
                    (Dwyer and Piper 1987). Young Atlantic salmon can tol-             The embryo has a lower lethal level of about pH 3.5 during
                    erate temperatures up to 27' C for short periods but seek          early cleavages and pH 3.1 just before hatching (Peterson
                    cooler water as these temperatures are approached (De-             et al. 1980). However, a pH of 4.0-5.5 delays hatching. A
                    Cola 1970). Juveniles withstand 32' C briefly (Huntsman            pH less than 5.0 inhibits enzymes necessary for hatching,
                    1942), and the lethal temperature under laboratory condi-          and reproduction fails (Haines 1981). Yolksac fry in situ
                    tions is about 320 C (Garside 1973). Tolerance polygons            had 100% mortality at pH 5.1 with high aluminum and








                    4 BIOLOGICAL SCIENCE REPORT 3



                    65% mortality at PH 5.7 with lower aluminum (Norrgren            Canadian streams to be 32 cnits, andjuveniles were absent
                    and Degerman 1993).                                              in areas with a mean column velocity exceeding 120 cm/s.
                       Juvenile Atlantic salmon are often exposed to low pH          Fry were most abundant in stream sections where mean
                    along with other stresses, such as swift water, toxic metals,    column velocity was less than 30 cm/s, but some fry were
                    and turbidity. The low PH causes edema of the gill lamella       observed at mean column velocities up to 60 cm/s (Heg-
                    and may disrupt respiration and excretion at times when          genes et a]. 1990).
                    metabolic demands are high. In the laboratory, juveniles            The velocity in microhabitats selected by fish was less
                    had a'lower lethal PH of 4.0 after 28 days of exposure           than the mean column velocity. The mean velocity in the
                    (Daye and Garside 1977, 1980). Concentrations of so-             microhabitat where fry hold was 17 cm/s in one stream and
                    dium, calcium, and chloride declined in the plasma after         5 cm/s in another (Trial and Stanley 1984). In Canadian
                    exposure to PH 4.6 but not at PH 5.0 or 5.5 (Fanner et al.       streams, fry preferred 0-5 cm/s in one stream and 17-
                    1989).                                                           21 cm/s in another (DeGraff and Bain 1986). The mean
                       An SI was developed with this literature information in       velocity where fry held position was 12 cm/s; most selected
                    which frequency of acidic episodes and their intensity are       velocities of 5-19 cm/s (Morantz et al. 1987). Gibson (1993)
                    key variables. Although aluminum and other metals are            reported that the mean velocity where fry held position was
                    obviously important in the manifestation of acidic effects,      13 cm/s in riffles and pools. In the laboratory, the velocity
                    we could not incorporate such information into a simple          where fry can no longer hold position was 150 cm/s at 6-8'
                    model. In general, HSI models do not consider toxic              C and 190 cm/s at 12-14' C (Heggenes and Traaen 1988).
                    substances. The intent is for the models to predict the          Trial and Stanley (1984) reported that 3-month-old Atlantic
                    quality of habitat in the absence of specific contaminants       salmon could maintain position in a flow tank in a velocity
                    and myriad other confounding factors.                            of 50 cm/s at 16' C and PH 4.5-6.0 cm. Below pH 4.0,
                    Velocity                                                         however, they were unable to maintain position in velocities
                                                                                     faster than 42 cm/s. Even in this flow tank, the fry were able
                       Atlantic salmon in fresh water require flowing water,         to find pockets with currents that were 60-70% of those
                    although they will occupy slow-moving or lentic habitats         measured.
                    (Einarsson et al. 1990; Cunjak 1992). Adults select spawn-          Competition between size groups is reduced by habitat
                    ing sites in riffles where the average velocity is about 50      segregation (Gibson et al. 1993). Yearling Atlantic salmon
                    cm/s (Elson 1975; Beland et al. 1982). The lower limit of        Parr have about the same velocity preferences as fry. The
                    velocity was 15-20 cm/s, and the upper limit was related         older and larger Parr take the best territories, usually in
                    to female size (e.g., a 50-cm female would be limited to         midstream. Habitat selection toward the middle of the
                    velocity less than 100 cm/s; Crisp and Carling 1989).            stream was evident from measuring where Parr occurred
                       Egg incubation requires upwelling of ground water or          relative to the shore-18 fish were 0-0.2 in from shore,
                    percolation of stream water through the gravel substrate,        121 were 0.3-0.7 in from shore, and 266 were 0.8-1.5 in
                    which is measured with a standard permeability test in           from shore (Hesthagen 1988). In some streams fry prefer
                    which the rate of water dispersal from apipe is determined.      riffles and Parr prefer runs (Tremblay et al. 1993). As
                    Permeabilities of 1.3-1.4 L/h are typical (Gustafson-Mar-        juveniles grow, they are able to cope with the faster water
                    janen and Moring 1984).                                          and thus benefit from more drifting food (Morantz et al.
                        Newly emerged fry occupy areas with current but              1987). They minimize energy expended on swimming by
                    select microhabitat with slower water. In an artificial          utilizing low-velocity areas, hiding among rocks in riffles
                    stream, newly emerged fry dispersed fastest when in a low        and darting into the swifter current only to feed. The most
                    velocity of about 8 cm/s (Crisp 1991). More stayed in the        favorable territories in some streams were in faster water,
                    stream at velocities of 25-70 cm/s, implying that the faster     in others slower, possibly because of other factors, such as
                    velocity was more suitable for fry. There was considerable       cover. Trial and Stanley (1984) reported that the velocity
                    variation in how velocity was measured, reported, and            in the microhabitat occupied by yearling Parr in one stream
                    interpreted. The prevailing velocity may be as important         was 9 cm/s, which was slower than in the areas occupied
                    as that where thejuvenile actually rests. The mean velocity      by fry, and 6.5 cm/s in another stream, which was faster
                    in the water column in areas preferred by first-year fish is     than in areas occupied by fry.
                    50-65 cm/s (Symons and Heland 1978). Knight et al.                  The gradients of streams where juvenile salmon occur
                    (1981) reported that the preferred habitat had a mean            range from 2 to 12 m/km (Elson 1975). In rivers in Nova
                    column velocity of 14 cm/s. The preferred mean column            Scotia, the highest densities of Parr were at a gradient of
                    velocity was 10-31 cm/s in one Canadian stream and               1.2-1.4% (Amiro 1993). Such gradients generate mean
                    10-46 cm/s in another (DeGraff and Bain 1986). Morantz           column and microhabitat velocities within the preferred
                    et al. (1987) reported the mean column velocity in eight         ranges for fry and Parr. Knight et al. (1981) found that







                                         HABiTAT SurrABiLiTy INDEX MODELS: NoNAaGRATORY FRESHwATER LIFE STAGES OF ATLANTIC SALMON 5



                    yearlings occupied stations where the mean velocity was 14         were abundant, mean depth ranged from 10 to 31 cm (Fran-
                    cm/s. Based on distribution in one stream, most Parr pre-          cis 1980). The preferred depths for fry in one stream in
                    ferred a mean column velocity of 10-24 cm/s; in another            Newfoundland were 13-25 cm and in another, 20-60 cm
                    stream, Parr preferred 16-57 cm/s (Degraff and Bain 1986).         (DeGraff and Bain 1986). In Newfoundland, fry occurred at
                    The mean column velocity selected by small Parr (about 85          17 cm depth in riffles and 32 cm in pools (Gibson 1993). In
                    mm long) was 40 cm/s and by large Parr (about 120 mm.)             eight streams in Nova Scotia and New Brunswick, the
                    35 cm/s (Morantz et al. 1987). Gibson (1993) reported, how-        average depth used by fry was 35 cm; most individuals were
                    ever, that small (6-10 cm) and large Parr (>10 cm) were            found between 20 and 40 cm (Morantz et al. 1987). In a
                    located at a mean velocity of 20 cm/s in riffles. In pools,        Norwegian stream, fry were mostly in waterless than 60 cm
                    however, small Parr selected velocity of 6 cm/s and large          deep (Heggenes et al. 1990). In England, in water less than
                    Parr 13 cm/s. The most preferred holding velocity of Parr,         20 cm deep, fry outnumbered Parr, whereas in water deeper
                    was 0-5 cm/s in one stream and 16-21 cm/s in another               than 20 cm, Parr were more abundant (Kennedy and Strange
                    (Degraff and Bain 1986). Large Parr were found in velocities       1986). In another English stream, the number of fry was
                    of 22 cm/s but preferred velocities of 10-20 cm/s (Morantz         positively correlated with depth up to 20 cm and inversely
                    et al. 1987). Larger Parr occupied microhabitats with veloci-      correlated with depth greater than 20 cm (Egglishaw and
                    ties of 0-25 cm/s in streams with mean velocity of overlying       Shackley 1985).
                    water of 0-75 cm/s (Heggenes et al. 1991).                            Parr seem to prefer deeper water than fry (Gibson 1993;
                        In fall, 2-year-old juvenile Atlantic salmon moved from        Gibson et al. 1993), which is usually found midstream.
                    the riffle area of streams into slower water, where they           Selection within streams is affected by availability of deep
                    remain during winter, whereas I -year-old juveniles did not        water with suitable velocities related to stream morphol-
                    move (Rimmer et al. 1984). Huntingford et al. (1988) found,        ogy. As with fry, the average depth selected by Parr varies
                    however, that all fish sought areas of low flow in fall. In        among streams and therefore among studies. The mean
                    winter, Parr hide under rocks in riffle areas with overlying       depth of preferred areas for Parr in one New England
                    velocities of 38-46 cm/s (Cunjak 1988). Parr destined to           stream was 29 cm (Knight et al. 1981), 49 cm in another,
                    become smolts the following year selected faster currents in       and 33 cm in a third (Trial and Stanley 1984). In some
                    an artificial stream than did Parr destined to remain in fresh     Canadian streams, Parr preferred depths of only 10-15 cm
                    .water for 2 years (Huntingford et al. 1988).                      (Symons and Heland 1978), whereas in two other streams,
                        Suitability indices were developed for velocities meas-        preferred depths were 22-42 cm and 14-48 cm (DeGraff
                    ured at 0.6 of total depth of the water column or below. The       and Bain 1986). The range of depths preferred by Parr
                    lower portion of the water column is where the fish spend          differed in eight Canadian streams; most occurred between
                    most of their time, and velocity at 0.6 of the total depth         30 and 60 cm (mean 47 cm; Morantz et al. 1987), In
                    approximates the average velocity for the water column             Newfoundland, small Parr (6-10 cm) were found in 22 cm
                    (Hamilton and Bergersen 1984). We had insufficient veloc-          of water in riffles and 42 cm in pools (Gibson 1993). Large
                    ity data to develop a fall or winter SI for velocity.              Parr (>10 cm) used slightly deeper areas, 24 cm in riffles
                                                                                       and 57 cm in pools. In Europe, yearlings were most abun-
                    Depth                                                              dant at a depth of 35 to 40 cm in one stream (Kennedy and
                        Spawning sites are selected at the tails of pools that are     Strange 1986) and deeper than 25 cm in another (Eg-
                    near the beginning of riffles. The depth depends on the size       glishaw and Shackley 1985). Most yearling or older Parr
                    of the stream and the size of the fish. A 50-cm female             occupied habitats with depths less than 90 cm (Heggenes
                    requires depths of 10-40 cm (Crisp and Carling 1989). In           et al. 1990). Larger Parr used depths between 25-and
                    Maine rivers, the average depth over spawning redds was 40         85 cm, but a few were in water deeper than 100 cm
                    cm (Beland et al. 1982); in New Brunswick, it was 20 cm            (Heggenes et al. 1991).
                    (Peterson 1978).                                                      Suitability indices were developed for depth over spawn-
                        After hatching, fry disperse and establish territories. Fry    ing areas and at summer low flows for fry and Parr. We had
                    establish residence in shallower water nearer shore. The           insufficient data to develop a winter S1 for depth over redds.
                    depths where fry reside in each stream are related to stream       However, because most fish descend into the substrate in
                    morphology, which determines the depth of near-shore areas         winter, we believe that the summer depth SI's for fry and
                    at low flows. Thus, average depth selected by fry will vary        Parr are also applicable to winter low flows. In winter, Parr
                    among streams. Knight et al. (198 1) reported that fry habitat     occupy riffles in water 41-49 cm deep (Cunjak 1988).
                    in New England streams averaged 25 cm deep (range 9-39             Substrate, Sedhnent, and Turbidity
                    cm). In Maine, fry preferred water 34 cm deep in one stream
                    and 27 cm in another (Trial and Stanley 1984). In Canada,             Adults select spawning sites at the tails of pools that have
                    for 62 sites on New Brunswick streams and rivers where fry         substrate composition reflecting sorting by the swift currents







                   6 BioLoGicAL ScniNcE REPoRT 3



                   that move over this habitat. In Peterson's (1978) study, the     interference with sight feeding and growth is possible. In
                   particle size composition was 0-3% fine sand (0.06-              the laboratory, coho salmon (Oncorhynchus kisutch) and
                   0.5 mm), 10-15% coarse sand (>0.5-2.2 mm), 40-50%                steelhead (0. mykiss) grew fastest in clear water; growth
                   pebble (>2.2-22 mm), and 40-60% cobble (>22-256 mm).             was inhibited at 45-50 NTU (Sigler et al. 1984). In some
                   Spawners preferred gravel of 20-30 nun diameter (Crisp           tests, 38-49 NTU did not inhibit growth, and in other tests
                   and Carling 1989). The substrate composition of the redds        turbidity as low as 25 NTU inhibited growth. When coho
                   of landlocked Atlantic salmon included higher percentages        salmon were exposed to turbidities of 30 and 60 NTU,
                   of intermediate-size particles (Warner 1963). The land-          territoriality deteriorated and prey capture rates declined
                   locked fish, which are smaller than the sea-run fish, may not    (Berg and Northcote 1985). Coho salmon avoided turbid-
                   be capable of moving the larger particles.                       ity of 70 NTU (Bisson and Bilby 1992). Episodes of high
                      Because juvenile salmon occur in the riffle area of           turbidity seem to do no harm, and turbidity alone corre-
                   streams, they are likely to be found above substrate contain-    lated poorly with effects of suspended sediments on fish
                   ing sand, gravel, and cobble rather than silt. In one stream,    (Newcombe and MacDonald 1991). Relatively low tur-
                   Atlantic salmon fry selected a substrate classified as 4.8,      bidities over long periods caused reduced feeding in sev-
                   based on an index in which 3 represents fines and detritus;      eral species of salmonids (Newcombe and MacDonald
                   4, sand; 5, gravel; and 6, cobble (Trial and Stanley 1984), @n   1991). Turbidities exceeding 1,150 standard units, meas-
                   two Canadian streams, the most preferred substrate had an        ured with a photometer during fall freshets, did not injure
                   index of 4.5-5.5 for fry and parr (DeGraff and Bain 1986).       or kill Atlantic salmon fry or parr (McCrimmon 1954).
                   In eight other Canadian streams, this index was 5.6 for fry,        The SI for turbidity was based on effects on other
                   5.9 for small parr, and 6.4 for large parr, indicating selection species of salmonids, primarily as reported in the review
                   of a coarser substrate as juveniles grow (Morantz et al.         by Newcombe and MacDonald (1991).
                   1987). During their first year, juveniles preferred gravel
                   substrate (16-64 mm), whereas yearling parr preferred a            Habitat Suitability Index (HSID
                   boulder and rubble substrate where diameters were greater                                Models
                   than 260 mm (Symons and Heland 1978). Gibson (1993)
                   concluded that fry are most common where there is a pebbly
                   bottom, and parr over coarser substrate. In a Norwegian                     APPlicability of the Models
                   stream, firy were observed over a gravel to boulder substrate,      Potential users of the HSI model for Atlantic salmon
                   and parr occupied a wider range of substrate types (Heg-         can have confidence in applying the model in habitats
                   genes et al. 1990).                                              where the model was developed and tested. Considerable
                      Depth, velocity, and substrate are interdependent. Sub-       effort has gone into validating the model, especially for the
                   strate is related to velocity, and velocity is affected by       more important variables. The model is equally applicable
                   depth. It is difficult to determine whetherjuveniles, as they    to anadromous and landlocked populations of juvenile
                   grow, select larger substrates, faster velocities, or deeper     Atlantic salmon. We recommend the use of this HSI model
                   areas with similar substrate and velocity. However, all          to help formulate expert opinion on habitat quality. How-
                   variables seem to be differentially selected by fry and parr.    ever, we caution that the model is a hypothesis describing
                   Our SI's were constructed so that pebble-size substrates         a simplified version of complex interrelationships within
                   were best for fry and cobble substrates best for parr.           a seasonally dynamic environment. In addition, the model
                      Sedimentation into the spaces between pebbles and             concerns a species with shifting habitat requirements,
                   cobble interferes with the use of this space as shelter for      complex behaviors, and a long life cycle. Furthermore, this
                   young Atlantic salmon and decreases their survival rate in       HSI model does not consider toxic chemicals, which if
                   summer (McCrimmon 1954). In winter, siltation and sus-           present may limit the application to predicting what habitat
                   pended debris within the substrate are also important be-        quality would be if the contaminant were removed.
                   cause fish hide in spaces under rocks (Cunjak 1988). Such
                   sedimentation obviously also affects benthic production          Geographical Area
                   and reproductive success. .                                         The HSI model was designed for Atlantic salmon in
                      Atlantic salmon typically occur in clear streams and          streams of New England and the Canadian maritimes of
                   depend on transparent water for site-feeding. Turbidities        temperate North America. The model applies to embryos,
                   of 40 nephelometric turbidity units (NTU) or less are            fry, and parr in streams and to adults only in regard to the
                   considered to represent clear water that is highly suitable      selection of spawning sites. European populations share
                   for feeding. Survival of fry and parr was highest in stream      many of the same characteristics as the North American
                   segments with the lowest base turbidities (McCrimmon             populations, and the model could probably be applied to
                   1954). As turbidities increase to 100 NTU, progressive           European populations with little modification.







                                        HAMAT SurrABELny INDEX MODELS: NONMIGRATORY FRESHWATER LWE STAGES OF ATLANTIC SALmoN 7



                    Season                                                           1990). Parr then disperse gradually over the summer to
                       The water quality, fry, and parr components of the HSI        occupy all suitable stream habitats. In winter, older parr
                    model are designed to evaluate the summer habitat ofjuve-        move from the riffles in streams into slower waters (Rim-
                    nile Atlantic salmon during base flow, when the extent of        mer et al. 1984). Dispersal was faster for parr planted in
                                                                                     deep, slow water than for parr planted in their preferred
                    the available habitat is limited. The reproductive component
                    obviously applies during the fall period. Winter habitat may     habitat of fast-moving water (Heggenes and Borgstrom
                    be particularly important to the survival of Atlantic salmon;    1991). For most of these dispersal phases, the extent of
                    for example, low winter discharge significantly affects ju-      movements is unknown.
                    venile survival (Gibson and Myers 1988). Except for tem-         Ve6fication Level
                    perature and ice, the habitat occupied by juveniles differs
                    only slightly from summer habitat (Rimmer et al. 1984;              Originally, the SI's and HSI model presented here were
                    Cunjak 1988). Although survival is correlated with winter        derived from literature values and initially tested in Maine
                    air temperatures and water levels (Chadwick 1982), no            streams (Trial and Stanley 1984; Trial et al. 1984). Suitabil-
                    measurements link specific winter conditions to embryo or        ity indices for water depth, velocity, and substrate were
                    juvenile survival.                                               independently developed and tested in Canadian streams
                                                                                     (Morantz et al. 1987). A third test for validation was done in
                    Habitat Types                                                    Maine streams (Trial 1989). A fourth test was done in which
                       The HSI model applies to embryos and juveniles in             Trial (1989) analyzed data collected in New Brunswick by
                    freshwater, riverine (lotic) habitat. The model describes the    Francis (1980) and Trial (1989). Recently, SI's developed
                    area where spawning and egg incubation occur, as well as         for Newfoundland rivers were tested and found to consis-
                    nearby nursery areas for juveniles. The model does not           tently predict standing crop of fry (Scruton and Gibson
                    consider the lake and marine feeding grounds of adults or        1993).
                    any habitat characteristics critical to successful downstream       Trial (1989) formulated four alternative HSI models
                    or upstream migration in estuaries or freshwater streams.        based on an evaluation of SI's related to velocity, substrate,
                    The model has the most validity when applied to the streams      and depth. Two of the HSI models used SI's from Morantz
                    in which it was tested or to similar streams. Tests were done    et al. (1987) from the fry and parr components, and two used
                    in streams ranging from small brooks to the mainstem of          SI's from Trial and Stanley (1984). Trial (1989) determined
                    major rivers, such as the St. John River in New Brunswick.       the goodness of fit between the measured variables for
                                                                                     habitat selected by juveniles and the S1 values. In other
                    Minimum Habitat Area                                             words, the cumulative frequency distribution (CFD) of suit-
                       In HSI models, the n-dnimum habitat area usually in-          ability based on habitat selection by fish was compared with
                    cludes egg incubation areas, nursery and juvenile feeding        the hypothetical CFD. This process was done stepwise for
                    grounds, and adult feeding grounds. For Atlantic salmon, the     individual SI's and the life stage component indices pro-
                    usual definition of minimum habitat area does not apply          duced from either the product of the three SI's or their
                    because the habitats for the different life stages usually are   geometric mean. Trial's (1989) test of fry and parr compo-
                    not contiguous. Of critical importance to Atlantic salmon        nents indicated that the CFD from the SI's in Trial and
                    populations is free passage between the different habitats,      Stanley (1984) and Morantz et al. (1987) had a more gradual
                    unobstructed by dams or interception by excessive fisheries.     rise to 100% than the CFD from her data on fry in Maine
                       The area of habitat used by Atlantic salmon varies            streams. The apparent lack of fit of the components was
                    considerably. Some stocks of landlocked Atlantic salmon          expected because the Sl's were overestimates of the optimal
                    exist within a single river system in which spawning,            range of each habitat variable (Trial 1989).
                    nursery, and feeding areas are within a few kilometers of            In a second test, Trial (1989) found that thejoint prob-
                    each other, for example, the West Branch of the Penobscot        abilities and geometric means for the fry component index
                    River in Maine (Warner and Havey 1985). At the opposite          were correlated with the density of fry. The two ways of
                    extreme, some populations have nursery grounds in small          calculating component indices did not affect the ranking
                    streams in Portugal, and the adults feed in Arctic waters        of the sites-the ranks of the alternative component indi-
                    off the coast of Baffin Island in North America (Netboy          ces were correlated with the rank of fry density at 16 sites.
                    1974). The minimum habitat area for the juvenile life            In contrast, none of the parr component models correlated
                    stages is poorly defined, in part because little information     with parr densities, probably because other variables, such
                    is published on distances for the dispersion of fry and parr.    as cover, were important. For total numbers of juveniles,
                    Dispersal occurs rapidly in spring as fry emerge from the        three of the four HSI models were correlated with popula-
                    redd and move predominantly downstream (McKenzie                 tion density, and only the model based on joint probability
                    and Moring 1988; Gustafson-Greenwood and Moring                  and the SI's by Morantz et al. (1987) was not correlated,







                    8 BIOLOGICAL SCIENCE REPORT 3



                    These tests of HSI models verified the HSI approach                most conservative approach for modeling life stage suitabili-
                    toward evaluating habitat and validated some of the SI's,          ties. Because there was no difference in the statistical fit of
                    especially for the water velocity, depth, and substrate of         component indices calculated using the joint probability or
                    fry. These tests measured density, abundance, or site se-          the geometric mean (Trial 1999), we chose to use the model
                    lection as an indicator of carrying capacity. In general, the      that is easiest to use. Bain and Robinson (1988) expressed
                    microhabitat used within any one stream was narrower               concern that numerous variables in a geometric mean would
                    than predicted by the models, whereas the range of habitats        result in an unrealistic degree of compensation for the lowest
                    used among streams was predicted accurately. Scruton and           values. Therefore, we used a joint probability approach to
                    Gibson (1993) noted that SI's are more useful if derived           calculate component indices.
                    from macrohabitat measurements (e.g., stream width)
                    rather than microbabitat (e.g., variables measured at loca-        Water QuAty
                    tion of individual fish).                                            The water quality component was modeled by a mini-
                       In tests of HSI models by Trial (1989), the reproductive        mum value. Fry (1971) and Bren (1979) recommended this
                    component was based on water quality and stream order.             model for limiting and lethal factors. The water quality
                    Thus, the complete reproductive component, which consists          component in Trial and Stanley's (1984) model consisted of
                    of variables for depth, velocity, spawning temperature, in-        water temperature, pH, turbidity, and n-dnimum oxygen.
                    cubation temperature in winter, stream order, and dominant         This component was not correlated with observed densities
                    substrate (Trial and Stanley 1984), was not tested ade-            for fry or parr (Trial 1989). Because the two temperature
                    quately.                                                           variables, maximum and average temperature, were within
                       The models tested by Trial (1989) did not include food          the tolerance range for juvenile Atlantic salmon at all sites,
                    availability because of the difficulty in sampling food            the component index did not discriminate differences. How-
                    abundance for an animal with opportunistic feeding habits.         ever, temperature might profoundly affect biomass or
                    A surrogate measure for food might be possible, based on           growth rate, should these be used as end point measurements
                    variables related to the productivity of food of salmonids,        for testing comp
                    such as alkalinity and conductivity (McFadden and Coo-                             onent indices. Growth ofjuvenile salmon is
                    per 1962; Cooper and Scherer 1967).                                highly dependent on temperature (Egglishaw and Shackley
                                                                                       1985).
                                     Model Description                                     Suitability Index Graphsfor Model
                       The implicit assumption of HSI models is that habitat                                   Variables
                    with high HSI values has high carrying capacity and high
                    productivity potential. These models were developed to               The SI for each variable, as a function of the environ-
                    predict the effects of environmental changes by relating           mental range for that variable, is shown graphically in this
                    environmental conditions to carrying capacity (U.S. Fish           section. Habitat suitability indices can be computed with the
                    and Wildlife Service 198 1). The aquatic and fish species HSI      following SI's, which we modified from Trial and Stanley
                    models provide a systematic method for evaluating projects         (1994), based on new literature and Trial (1989). Trial
                    that may alter the habitat of indicator species.                   (1989) discussed the assumptions associated with construct-
                                                                                       ing the SI's, and assumptions are also discussed in sections
                    Life Stage Component Indices                                       below.
                       The previously published model (Trial and Stanley 1984)            Field use of these SI's requires measurements of key
                    defined parr component suitability as the geometric mean of        environmental variables. Methods for sampling habitat are
                    the SI's for velocity, depth, and substrate. A geometric mean      described in detail in Terrell et al. (1982), along with some
                    increases the most when the individual variable with the           shortcuts applicable to less rigorous studies. A multimillion
                    lowest value is increased. In contrast, an arithmetic mean         dollar project with great potential for widespread damage
                    changes the same amount for a fixed amount of increase in          might warrant a full-scale study with multiyear sampling. A
                    a single variable, regardless of which variable is increased.      local project with probable minimal impact might require
                    We describe component models in which the quality of               only a single visit to the site during summer base flow. Users
                    holding or redd sites is based on multiplication of three          must decide on the level of sampling required but should not
                    variables (velocity, depth, and substrate) with values on a        compromise on the methods recommended by Terrell et al.
                    scale of 0 to 1.0. If the SI for a variable is considered to be    (1982). Alternative methods forgathering data on individual
                    aprobability ofhabitat utility, then the component suitability     variables were discussed by Hamilton and Bergersen
                    would be a product of the individual variable values. We           (1984). As with the overall sampling plan, the method
                    believe this "joint probability" approach for combining ve-        selected to measure a variable may be dictated by the scope
                    locity, depth, and substrate suitabilities is biologically the     of the project.







                                                                 HABrrAT SurrAwLrry INDEX MODELS: NONNUGRAToRy FRESHwATER LiFE STArEs OF ATL_4NnC SALmON 9



                                                                                                         Water Quality Component


                                           VI: Mean maximum daily water temperature for the warmest contiguous                                      V2: Mean water temperature for the growing season or summer,
                                                      3-day period of summer during bass flow, preferably taken from a                                        preferably taken with a hydrothermograph.
                                                      continuous temperature record O.e., hydrothermograph).                                           1.0-                            --------------
                                              1.0     --------

                                                                                                                                                    X
                                                                                      T        SI                                                   (P
                                           X                                                                                                        13
                                                                                      is       1.0
                                                                                      20       1.0                                                                                          31
                                                                                                                                                       0.5 -
                                                                                      25    0.25-0.75
                                                                                                                                                                                       8    0.25
                                              D.5                                     30       0.0
                                                                                                                                                                                    14      1.0
                                           IZ                                         40       0.0                                                  U)                              18      1.0
                                                                                                                                                                                    20      0.6

                                                                                                                                                       0.0
                                                                                                                                                              8     to       12        14         is         IS   20
                                              0.0 -                                                                                                                       Temperature CC)
                                                      15    20              25   30          35       40
                                                                Temperature CC)                                                                     V4: Mean minimum daily oxygen saturation for the 3-day
                                                                                                                                                              period with the lowest percent saturation during the
                                                                                                                                                              summer, Ideally monitored continuously.

                                                                                                                                                       1.0                                        ------------

                                           V&         Mean turbidity based on monthly measurements over as much
                                                      of the year as possible.                                                                      X
                                                                                                                                                    a)
                                              1.0     -------------                                                                                                                                  %
                                                                                                                                                                                                  saturation      at
                                                                                                                                                    Al' 0.5 -                                                0    0.0
                                           X                                                                                                                                                         40           0
                                                                                                                                                                                                     so           '@O
                                           a)
                                                                                                                                                    ft
                                                              NTU           I                                                                       C0                                               100          1.0

                                              0.5-               0          .0

                                                                40          .0                                                                         0.0
                                                               100          0.2                                                                               0         20        40        so               so   IDD
                                           CO)                                                                                                                                % Saturation



                                              0.0
                                                      0       20            40       so        80       100
                                                                            NTU                                                                     V& Minimum pH -The frequency at which critical
                                                                                                                                                              pH levels are reached, as measured during
                                                                                                                                                              episodes of acid runoff over 3-day periods.















                                                                                                                                                       0.0
                                                                                                                                                                   A             B                c          D

                                                                                                                                                              pH
                                                                                                                                                       Category                Description                   S.I.


                                                                                                                                                              A           pH below 4.0 at                    0.05
                                                                                                                                                                          least once annually

                                                                                                                                                              B           pH 4.0 to 5.5 at                   0.40
                                                                                                                                                                          least once annually


                                                                                                                                                       I      C           pH occasionally                    0.70
                                                                                                                                                                          falls below 5.5 but
                                                                                                                                                                          never Wow 5. 0


                                                                                                                                                              D           pH always 5.5 to 8.8               1.00
                                                                            S

                                                                            I

                                                                            I








                                   10 BIOLOGICAL SCIENCE REPORT 3



                                                                                                                                Fry Component
                                   If mean stream depth is greater than 50 cm, divide the stream into fourths. Because fry occur mostly in the shallower
                                   sections, average the variables for the two shallowest fourths of the section to arrive at a mean value for each SI of
                                   the fry component. In streams shallower than 50 cm, simply average the entire stream.





                                                 V6:       Mean column velocity for fry during base summer flow.                                                    VT         Dominant substrate for fry.
                                                           Measuring at a point 0.6 x total depth from the surface
                                                           approximates mean column velocity.                                                                              1.0
                                                                                                                                                                                                                  ............
                                                                                                                                                                                                                  ............
                                                                                                                                                                                                                  ... ........
                                                                                                                                                                                                                  .... .......
                                                                                                                                                                                                                  . ........ .
                                                                                                                                                                                                                  . ........ .
                                                                                                                                                                                                                  .......... .
                                                                                                                                                                                                                  ............
                                                                                                                                                                                                                  . ........ .
                                                      1.0-                       -------
                                                                                                                                                                                                                  ............
                                                                                                                                                                                                                  ..........
                                                                                                                                                                      X                                                  .... ...


                                                                                                                                                                                                                         ...... .. .....
                                                                                                                                                                                                                            .. .... .....
                                                 X
                                                                             Velocity       Sl
                                                                                                                                                                                                                  ... ........ ........
                                                                                                                                                                                                                  .... ...... . . ..
                                                                                                                                                                                                                  .... ...... ... ......
                                                                                                                                                                                                                  ... ........ ..
                                                                                    0
                                                 C:                                                                                                                        0.5 -
                                                                                                                                                                                                                  .......... .
                                                                                                                                                                                                     ........ ..  .. ........ .. . ..
                                                      0.5 -                      10
                                                                                                                                                                                                     ........ .............. ..     ..... ..
                                                                                            11-80
                                                                                                                                                                                                     ......... ..... .      ... .. .
                                                                                                                                                                                                     I......      ....   ...... .
                                                 Z                               30         1.0                                                                                                      .........    I...   ..... .
                                                                                                                                                                                                     ........ ... ........

                                                                                 40         0.9
                                                                                                                                                                                                                     ........ ...
                                                                                                                                                                                                                         ...... ... .. ..

                                                                                                                                                                                                                     ........ ....    ......
                                                                                                                                                                                                     .. ......... .................. .....
                                                                                                                                                                                                     ......       I., .. .....I..... .....
                                                                                                                                                                                                     .. ..... ... .... ........     .... ...
                                                                                                                                                                                                     ........ ... ............. ..
                                                 Cl)                             so         0.1
                                                                                                                                                                                                     .. ........
                                                                                                                                                                                                     ............. .
                                                                                                                                                                                                     .. ..... ... ....
                                                                                 1          0.0                                                                                                      ...........


                                                                                                                                                                                                                  ...... .. .. ..... .... ..
                                                      0.0                                                                                                                                                                           .... :::::,
                                                                                                                                                                           0.0                                    1* 1 1              1
                                                               0              10            30             40           8WO           1 0                                                 1                       2      3           4              5
                                                                                    Velocity (cm/s)                                                                          Substrate               Substrate              Size
                                                                                                                                                                               Code                  Type                   (MM)                    sl
                                                                                                                                                                                    1                Fines                  < 0.5                   0.1         1
                                                                                                                                                                                    2                Sand                0.5- 2.2                   0.5
                                                                                                                                                                                    3            Pebble-gravel           > 2.2 - 22.2               1.0
                                                                                                                                                                                    4                Cobble              > 22.2 - 256               0.8         i
                                                                                                                                                                                    5                Boulder                > 256                   0.1





                                                                                                      VS:      Mean depth for fry during base summer flow.
                                                                                                           1.0              ------                                         Depth          Sl
                                                                                                                                                                                    0     0.0
                                                                                                                                                                               10         1.0
                                                                                                     X
                                                                                                    13                                                                         40         1.0
                                                                                                                                                                               70         0.2

                                                                                                           0.5-                                                                90         0.0
                                                                                                                                                                              100         0.0







                                                                                                           0.0
                                                                                                                   0      10 20 30 40 50 60                             70     80 90 100
                                                                                                                                              Depth (cm)







                                                                     HABrrAT SurFABu-rry INDEX MODELS: NONMIGRATORY FREsHwATER LEFE STAGES OF ATLANTIC SALMON I I



                                                                                                                               Parr Component
                                   If mean stream depth is over 50 cm, divide the stream into fourths, and average the variables in the two deepest
                                   fourths to arrive at the mean value for each SI. In streams shallower than 50 cm, use the mean values for the entire
                                   stream.





                                         Vg:       Mean column velocity for parr during bass summer flows.                                                    V10:          Dominant substrate for parr.

                                                                                                                                                                    1.0-

                                                              -----------
                                                                                                                                                                                                                    ...... .....

                                                                                                                                                                                                                    ...........
                                          x                                                                                                                    x

                                         Va
                                                                                                                                                                                                           ........    ...
                                                                 Velocity Sl                                                                                   C                                           ........ .....
                                               0.5                      0      0.8                                                                                  0.5-
                                                                                                                                                                                                       ............ .
                                                                                   0
                                                                L"00           I.                                                                                                                                    ...........
                                                                                   .0
                                                                                                                                                                                                       ...........

                                                                      so                                                                                                                                                      ... .....
                                                                               0.5
                                                                                                                                                                                                                       ......... .......
                                                                                                                                                                                                                      ............
                                                                     loo
                                                                               0.1
                                                                                                                                                                                                                            ..... ... ...
                                                                                                                                                                                                                     ...........  I .....  -
                                                                                                                                                                                                  .... ... ... ..... ..... ... .. .
                                                                                                                                                                                          ... . ..... ............    .......... ........ ...
                                                                                                                                                                                                    .. . .... ... ..
                                              O.D
                                                                                                                                                                                                             ...... .........   . ......   ....
                                                       0     10      20     30     40 @0 60 @0 @0 @0                        1@0                                     0.0                       ... ...
                                                                            Velocity (cm/s)                                                                                                   2             3              4               5

                                                                                                                                                                            Substrate     Substrate               Size
                                                                                                                                                                            Code             Type                (MM)                      sl
                                                                                                                                                                            1                Fines               < 0.5                     0.0

                                                                                                                                                                            2                  and              0.5-2.2                    0.2
                                                                                                                                                                            3           Pebbl&gravel          > 2.2 - 22.2                 0.7
                                                                                                                                                                            4               Cobble           > 22.2 - 256                  1.0
                                                                                                                                                                            5              Boulder               > 256                     0.3




                                                                                                  V1 1:      Mean depth for parr during base summer flows.


                                                                                                         1.0                   ----------                                   Depth   Sl
                                                                                                                                                                            0       0.0
                                                                                                    x                                                                       20      1.0
                                                                                                                                                                            so      1.0
                                                                                                                                                                            70      0.2
                                                                                                         0.5 -                                                              90
                                                                                                                                                                            100     00.'00


                                                                                                         0.0  0              2 0           @0             60                810         100
                                                                                                                                          Depth (cm)







                                    12 BIOLOGICAL SCIENCE REPORT 3



                                                                                                                     Reproductive Component

                                    Evaluate at the head or tail of pools only if the substrate material is > 2.2 to 256 mm in diameter and water is at least
                                    15 cm deep. The best time to conduct the field work would be in the fall, when Atlantic salmon are selecting spawning
                                    areas. Otherwise, attempt to estimate fall conditions by historical information on seasonal variation.

                                                   V1 2: Mean depth for reproduction at spawning time.                                                       V1 3:             Mean column velocity for reproduction during tail, or at flow
                                                                                                                                                                               conditions approArnating those occurring during fall.
                                                     1.0                 -------                              Depth                                                1.0-
                                                                                                                     0    D.0                                                                                                     %
                                                                                                                     a    0.0
                                                   a)                                                                10   0.5
                                                                                                                     20   1.0                                x
                                                                                                                     40   1Z                                 Q)
                                                                                                                     90   0.0                                                                                         velocity @l
                                                     0.5                                                        100       0.0                                S                                                        0           0.0
                                                                                                                                                                   015 -                                              25          0.0
                                                   :3                                                                                                        .0                                                       35          0.5
                                                   Cl)                                                                                                       .9
                                                                                                                                                                                                                      00          1.0
                                                                                                                                                             :3                                                       80
                                                                                                                                                             U)                                                                   ':o
                                                                                                                                                                                                                      90          16
                                                     0.0  0     1      @0           @0            @0            so          100                                                                                       100         0.0
                                                                                    Depth (cm)                                                                     0.0
                                                                                                                                                                               0      20           @O                 60          80     100
                                                                                                                                                                                            Velocity (cm/s)


                                       V14:        Spawning temperature - If water temperature reaches then declines                                               V15:        Embryo Incubation temperature - Average meAmum
                                                   below 112T In late October and early November, SI=1.0. Spawning                                                             daily temperature for the warmest 2-day perlod
                                                   will follow the date that water temperature reaches and maintains a                                                         betmen November 1 Sand May 1, prefilrably taken
                                                   temperature between 12* and rC.                                                                                             with a hydrothermograph left In the stream over winter.
                                            1.0                           --------                      *C           sl                                                        1.0        -------------
                                                                                                        0.0          0.0
                                       x                                                                                                                           x
                                       a)                                                               2.6          0.0                                           0)                              T  sl
                                       13                                                               7.0          1.0
                                                                                                                                                                                                   0  0.0
                                                                                                        12.0         1.0                                                                              0.8
                                            0.5 -                 11                                                                                                           0.5-
                                                                                                        >12.0        0.0                                                                           a  1.0
                                       .93                                                                                                                                                         7  1.0
                                       :3                                                                                                                                                          9  0.7
                                       co                                                                                                                          U)                              I 10.1
                                                              tI
                                                                                                                                                                                                   12 0.0
                                            0.0                                                                                                                                0.0 11
                                                   0              5                 10                  15              20                                                     0      2            4                  a8          10 12
                                                                     Temperature CC)                                                                                                      Temperature CC)


                                                   V16: SUeam order, based on stream branches having                                                               V1 7:       Dominant substrate for spawning and
                                                       permanent water flow.                                                                                                   embryo Incubation.

                                                                                                                                                                                                                                  ...........
                                                                                                                                                                                                                                  ...........
                                                   1.0-                                                                                                                        1.0
                                                                                                                                                                                                                      .. .. . .....
                                                                                                                                                                                                                      ..... . ...........


                                                                                                                                                                                                                      . . .........
                                                                                                  ... . ... ....                                                                                                      ... .....
                                                                                                                                                                   x
                                                                                                                                                                                                                      ..........  ..........
                                                                                                                                                                                                                      . .....     . ... ..
                                                                                                                                                                                                                      .. ...... ..
                                                   0,5                       ... ...
                                                                                                                                                                               0.5 -

                                                                                                                                                                                                                      ..........

                                                                                                                                                                                                                      . ..........
                                                   C0                                                                                                                                                                             .........
                                                                                                                                                                                                                      ...         .........
                                                                                                                                                                                                                      ... ..........

                                                   0.0
                                                                                                                                                                                                                      ......      ......... .
                                                                1              2                  3           4
                                                                            Stream Order                                                                                              1            2                  3

                                                                               Stream                                                                                          substrate           substrale          Size
                                                                                Order             SI                                                                              Code             Type               (MM)               81
                                                                                    1             0.5                                                                                 1            Flnee              @ 0.5             0.00
                                                                                    2             0.8                                                                                 2            Sand               0.5. 2.2          0.00
                                                                                                                                                                                      3            Pebble-gravel      > 22 - 22.2       0.95
                                                                                    3             1.0                                                                                 4            cobble             > 7.2 - 25a        1.00
                                                                                    4             1.0                                                                                 s            Boulder                        258   0.00







                                       HABrrAT SurrAffliriy INDEX MODELS: NoNmiGRAToRY FRESHWATER LWE STAGES OF ATLANTIC SALMON 13



                   HSI Determination                                                  fry and parr had suitability of 1.0 for a more restricted range
                   Water Quality Component                                            of velocities than SI's for mean column velocity. Similarly,
                       CWQ = lowest of V I, V2, V3, V4, or V5                         Rimmer et al. (1984) found that velocities selected by fry
                   Fry Component                                                      and parr were lower than velocities in the overlying water.
                       CFry = V6 x V7 x V8                                            We recommend measuring column velocity at 0.6 of the
                   Parr Component                                                     depth (i.e., at a point 60% of the way from the surface of the
                       CParr = V9 x VIO x V1 I                                        water column to the bed of the stream).
                   Reproductive Component                                                    Field Application of the Models
                         CR = lowest of V14, V15, V16, or V17
                   Habitat Suitability Index                                             For the mean maximum daily temperature for the
                         HSI = (CWQ x CFry x CParr x CR)                              warmest contiguous 3-day period of summer (VI), the
                       Some environmental situations might alter the appropri-        SI was based on maximum summer temperatures of
                   ateness of the HSI approach. For example, the presence of          streams with Atlantic salmon populations and upper
                   aluminum in combination with high acidity may affect               incipient lethal temperatures. The significance of maxi-
                   survival. Users may modify SI's based on local conditions,         mum temperature is confounded becausejuvenile Atlan-
                   carefully documenting the rationale for the changes. Like-         tic salmon avoid high temperatures. The 3-day period of
                   wise, the structure of the component and final HSI model           exposure corresponds to lethal exposure periods of some
                   may be modified.                                                   laboratory experiments. We recommend that hydrother-
                                                                                      mographs be placed in streams being evaluated. If by-
                          Rationale and Assumptionsfor                                drothermographs are not available, visit the stream dur-
                                Suitability Indices (SIs)                             ing periods of hot weather to get daily temperatures.
                                                                                         Embryo incubation temperature (V15) was based on
                       The SI's for Atlantic salmon represent the relation be-        the acute lethal temperatures for Atlantic salmon eggs
                   tween habitat variables and the population density of fry and      and embryos. The period of exposure reported in the
                   parr in freshwater streams; population density is assumed to       literature varied from 24 to 72 h. Thus, some considera-
                   indicate stream productivity. Another assumption is that           tion of the duration of lethal temperature was included
                   animals select suitable habitats, when available, that en-         in the variable label. The ideal way to measure this
                   hance individual survival. Optimal habitat has a suitability       variable would be to place hydrothermographs in or near
                   value of 1.0. Where optimal habitat is unavailable or already      the redds over winter. Without the equipment, the user
                   fully occupied, the number of survivors in suboptimal habi-        may have to measure stream temperatures, guessing at
                   tat indicates habitat suitability (with a value less than 1.0).    the times, based on episodes of warm weather (probably
                   Suitability indices are proportional to population density,        in spring). The mean temperature (V2) should be for the
                   which is determined by distribution and survival of the            growing season or summer-again we recommend a
                   species. The mean value of a habitat variable indicates            hydrothermograph. In addition, remember that V14 is
                   habitat suitability for the area where the measurement was         the temperature during spawning and that if water tem-
                   taken.                                                             peratures reach, then decline below 12' C in late October
                       We assumed that contaminants are absent. If contami-           and early November, spawning will follow when tem-
                   nants occur in the stream and their effects can be docu-           peratures are between 12' and 7' C.
                   mented, then the user might assign an HSI of zero.                    Calculate mean turbidity (V3) by month over as much
                   Alternatively, the HSI might be calculated as if no con-           of the year as possible. High turbidity during freshets is
                   taminant were present, with a qualification added that             not as important as chronic exposure, which has a sus-
                   this is the value if pollution remediation were imple-             tained inhibiting effect on feeding. The months during the
                   mented.                                                            growing season are most important. If available turbidity
                       While we recognize that competition between species            data are expressed as concentrations of suspended sedi-
                   and between life stages might be important, competition            ments (C) in mg1L, convert to NTU units with the formula
                   is not modeled. The HSI model is based on physical factors         NTU = 10 + 0. 178 C (Sigler et al. 1984).
                   only. The HSI value is stated as if competition were absent.          Mean minimum oxygen saturation (V4) was based on
                       The velocity that Trial (1989) reported was measured           acute tolerances of Atlantic salmon to low dissolved oxygen
                   where fish were actually located, which was usually less           concentrations at several temperatures and the average con-
                   than the average column velocity. Morantz et al. (1987) and        ditions of streams that have populations. If low percent
                   DeGraff and Bain (1986) measured mean velocity of the              saturation of oxygen persisted for no more than I day, then
                   water column and the velocity selected by each individual.         the suitability of the habitat would be higher than if oxygen
                   In both papers, the SI's developed for velocities selected by      was low for an extended period. We recommend taking daily







                     14 BIOLOGICAL SCIENCE REPORT 3



                     measurements in the early morning on a cloudy day during            The HSI should be treated as a linear index to the carrying
                     the warmest summer periods. A recording oxygen probe in          capacity of the particular habitat-the higher the HSI value,
                     the stream would be ideal.                                       the more fish the habitat should be able to support. However,
                        Minimum pH (V5) was based on the acute lethal pH for          only physical and chemical characteristics of a habitat are
                     Atlantic salmon eggs and embryos. The period of exposure         considered. Biological interactions and the effect of barriers
                     reported in the literature varied from 24 to 72 h. Thus, some    are ignored. Predation, human harvest, competition, and
                     consideration of the duration of lethal pH was included in       nutrition are not considered, even though they would obvi-
                     the variable label. In addition, V5 includes consideration of    ously affect survival, density, or carrying capacity. For
                     frequency of low pH events. Other variables, such as alurni-     Atlantic salmon, habitat is often uninhabited because dams
                     num, affect survival to acid exposure-users are encouraged       block access. Nevertheless, the model could assign a high
                     to modify the SI if appropriate data are available for specific  HSI, indicating the potential to support salmon spawning if
                     sites.                                                           there were no barriers.
                        The area and time for calculating the mean for several of        All models represent simplifications of complex sys-
                     the variables were stated in Terrell et a]. (1982), but we will  tems. The purpose of HSI models is to help predict the
                     repeat them to avoid confusion. We recommend that meas-          responses of key species to development projects or
                     urements be made at five transects, 10 in apart, across the      management practices. These models may be useful for
                     stream. Establish the position of the first transect at random,  presenting simple alternatives to managers so that ra-
                     such as at the position where a ball lands. Measure current,     tional decisions can be made with data gathered at mod-
                     depth, and substrate at I-m intervals across the stream, or at   est costs. The HSI model approach has been widely
                     0.25, 0.5, and 0.75 of the width if streams are less than 2 in   accepted because it provides a rational approach for
                     wide. For spawning riffles, take a measurement at the head,      evaluation of habitat that does not depend solely on the
                     tail, and center of the riffle. Bottom substrate is calculated   opinion of experts. We prefer that our model be used by
                     by summing the linear amount of each type.                       experts as an aid to systematically applying their knowl-
                        Lack of suitable water quality at a site or in a river        edge to complex problems.
                     system can limit the distribution of the species. The
                     disappearance of Atlantic salmon from European and                       Sources of Additional Models
                     Canadian rivers coincident with decreased pH is evi-
                     dence of a limiting factor (Haines 1981; Watt et al.                The  National Biological Service, Midcontinent Eco-
                     1983). Thus, the water quality component was included            logical Science Center, in Fort Collins, Colorado, main-
                     in the HSI as potentially limiting. However, habitats for        tains a library of SI's for use with the Instrearn Flow
                     all life stages are not necessary at each site for reproduc-     Incremental Methodology.
                     ing populations because interspersion of habitats may               The Canadian Department of Fisheries and Oceans,
                     provide for all of the species' needs. The Atlantic              St. John's, Newfoundland, has developed SI's to evalu-
                     salmon's life cycle requires that some habitats exist            ate habitat for the various freshwater life stages of At-
                     within the drainage for each riverine life stage. The            lantic salmon in Newfoundland (Scruton and Gibson
                     model user must be aware of the mix of different quali-          1993), and a workshop was held in 1992 to develop a
                     ties of life stage habitats within the study area and            model. The SI's were based on data on the density of
                     drainage. Calculating a species HSI that combines all life       juvenile Atlantic salmon and on the habitat from 242
                     stage components into one index obscures information             stations on 18 rivers on the island of Newfoundland.
                     but may be needed in an assessment. Thus, the model              Suitability indices consistently predicted densities of fry
                     includes component indices for water quality, reproduc-          based on important habitat variables. Suitability indices
                     tion, fry, and parr and a formula for the species HSI.           were most useful if based on macrohabitat measurements -
                                                                                      of stream dimensions and characteristics rather than on
                              Interpreting Model Outputs                              the microhabitat for the location of individual fish.
                                                                                         The U.S. Army Corps of Engineers has developed an
                        There are numerous possible applications of the HSI           Aquatic Habitat Appraisal Guide, based on the Habitat
                     model for Atlantic salmon. Potential users might differ          Evaluation Procedures, using 16 habitat variables and HSI
                     widely in their understanding of the premises and limi-          scores.
                     tations of the model. Only the most naive would take it             Two other National Biological Service ecological
                     11 off the shelf," make a few measurements in a target           science centers (located in Leetown, West Virginia, and
                     habitat, and attempt to make far-reaching conclusions.           Columbia, Missouri) are evaluating habitat requirements
                     Experts on life history and biology should be able to use        for adult Atlantic salmon and developing an improved
                     the model in the more realistic context described below.         approach for evaluating water quality requirements.







                                           HABrrAT SurrABiLrry INDEX MODELs: NONMIGRATORY FREsHwATER LiFE STAGES OF ATLANuc SALMON 15


                                    Acknowledgments                                           Curijak, R. A. 1988. Behavior and microhabitat of young Atlantic
                                                                                                  salmon (Salmo salar) during winter. Canadian Journal of
                         We thank James W. Terrell, Jeanette Carpenter, and                       Fisheries and Aquatic Sciences 45:2156-2160.
                     Henry E. Booke for reviewing earlier drafts of this manu-                Cunjak, R. A. 1992. Comparative feeding, growth and move-
                     script. Jeanette Carpenter produced the final SI graphs.                     ments of Atlantic salmon (Salmo salar) parr from fiverine and
                                                                                                  estuarine environments. Ecology of Freshwater Fish 1:26-34.
                                                                                              Danie, D. S., J. G. Trial, and J. G. Stanley. 1984. Species profiles:
                                                                                                  Life histories and environmental requirements of coastal fish
                                      Cited References                                            and invertebrates (North Atlantic)-Atlantic salmon. U.S.
                                                                                                  Fish and Wildlife Service FWS/OBS-82/11.22. U.S. Army
                     Amiro, P. G. 1993. Habitat measurement and population estima-                Corps of Engineers TR EL-82-4. 19 pp.
                         tion of juvenile Atlantic salmon (Salmo salar). Pages 81-97          Daye, P. G., and E. T. Garside. 1977. Lower lethal levels of pH
                         in R. J. Gibson and R. E. Cutting, editors. Production of                for embryos and alevins of Atlantic salmon, Salmo salar L.
                         juvenile Atlantic salmon, Salmo salar, in natural waters.                Canadian Journal of Zoology 55:1504---1508.
                         Canadian Special Publication in Fisheries and Aquatic Sci-           Daye, P. G., and E. T. Garside. 1980. Development, survival, and
                         ences Number 118.                                                        structural alterations of embryos and alevins of Atlantic
                     Bain, M., and C. L. Robinson. 1988. Structure, performance, and              salmon, Salmo salar L., continuously exposed to alkaline
                         assumptions of riverine Habitat Suitability Index models.                levels of pH from fertilization. Canadian Journal of Zoology
                         Alabama Cooperative Fisheries and Wildlife Research Unit.                58:369-377.
                         Aquatic Resources Research Series 88-3. Auburn, Ala. 20 pp.          DeCola, J. N. 1970. Water quality requirements for Atlantic
                                                                                                  salmon. U.S. Department of the Interior Federal Water Qual-
                     Beland, K. F., R. M. Jordan, and A. L. Meister. 1982. Water depth            ity Administration, Northeast Region, Boston, Mass. 42 pp.
                         and velocity preferences of spawning Atlantic salmon in              DeCola, J. N. 1975. Atlantic salmon restoration and the question
                         Maine rivers. North American Journal of Fisheries Manage-                of water quality. International Atlantic Salmon Foundation
                         ment 2:11-13.                                                            Special Publication Series 6:24-28.
                     Berg, L., and T. G. Northcote. 1985. Changes in territorial,             DeGraff, D. A., and L. H. Bain. 1986. Habitat use by and
                         gill-flaring, and feeding behavior in juvenile coho salmon               preferences ofjuvenile Atlantic salmon in two Newfoundland
                         (Oncorhynchus kisutch) following short-term pulses of sus-               rivers. Transactions of the American Fisheries Society
                         pended sediment. Journal of the Fisheries Research Board of              115:671-681.
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                     Bisson, P. A., and R. E. Bilby. 1982. Avoidance of suspended                 efficiency as affected by temperature. Progressive Fish-Cul-
                         sediment by juvenile coho salmon. North American Journal                 turist 49:57-59.
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                     Bley, P. W. 1981. Age, growth, and mortality ofjuvenile Atlantic             the production of juvenile Atlantic salmon in Scottish
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                         Biological Report 87(4). 25 pp.                                      Einarsson, S. M., D. H. Mills, and V. Johannsson. 1990. Utiliza-
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                         dian Journal of Fisheries and Aquatic Sciences 39:1496-1501.         Elson, P. F. 1975. Atlantic salmon rivers, smolt production and
                     Chadwick, E. M. P. 1985. Fundamental research problems in the                optimal spawning: An overview of natural production. Inter-
                         management of Atlantic salmon, Salmo salar L., in Atlantic               national Atlantic Salmon Foundation Special Publication Se-
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                     Cooper, E. L., and R. C. Scherer. 1967. Annual production of             Farmer, G. J., R. L. Saunders, T. R. Goff, C. E. Johnston, and
                         brook trout (Salvelinus fontinalis) is fertile and infertile             E. B. Henderson. 1989. Some physiological responses of
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                       16 BIOLOGICAL SCIENCE REPORT 3



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                       Garside, E. T. 1973. Ultimate upper lethal temperature of Atlantic         ada 5:485-501.
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                           ing, rearing and production. Reviews in Fish Biology and               extreme climates with special reference to some cold Norwe-
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                       Gibson, R. J., and R. A. Myers. 1988. Influence of seasonal river          ences 43:980-984.
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                       Gustafson-Greenwood, K. I., and J. R. Moring. 1990. Territory              shire 1975-1980. U.S. Fish and Wildlife Service, Laconia,
                           size and distribution of newly-emerged Atlantic salmon                 N.H. 14 pp.
                           (Salmo salar). Hydrobiologia 206:125-13 1.                          Lacroix, G. L., and D. R. Townsend. 1987. Responses ofjuvenile
                       Gustafson-lvla@anen, K. A., and J. R. Moring. 1984. Construc-              Atlantic salmon (Salmo salar) to episodic increases in acidity
                           tion of artificial redds for evaluating survival of Atlantic           of Nova Scotia rivers. Canadian Journal of Fisheries and
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                       Haines, T. A. 198 1. Acidic precipitation and its consequences for         of Canada. Bulletin of the Fisheries Research Board of Can-
                           aquatic ecosystems: A review. Transactions of the American             ada Number 155. 485 pp.
                           Fisheries Society 110:669-707.                                      Lear, W. H. 1993. The management of Canadian Atlantic salmon
                       Hamilton, K., and E. P. Bergersen. 1985. Methods to estimate               Fisheries. Pages 151-176 in L. S. Parsons and W. H. Lear,
                           aquatic habitat variables. Colorado State University, Ft. Col-         editors. Perspectives on Canadian marine Fisheries manage-
                           lins. 260 pp.                                                          ment. National Research Council of Canada, Ottawa, Ont.
                       Heggenes, J., and R. Borgstrom. 199 1. Effect of habitat types on       MacKenzie, C., and J. R. Moring. 1988. Estimating survival of
                           survival, spatial distribution and production of an allopatric         Atlantic salmon during the intragravel period. North Ameri-
                           cohort of Atlantic salmon, Salmo salar L., under conditions            can Journal of Fisheries Management 8:45-49.
                           of low competition. Journal of Fish Biology 38:267-280.             McCrimmon, H. R. 1954. Stream studies on planted Atlantic
                       Heggenes, J., A. Brabrand, and S. J. Saltveit. 1990. Comparison            salmon. Journal of the Fisheries Research Board of Canada
                           of three methods for studies of stream habitat use by young            11:362-403.
                           brown trout and Atlantic salmon. Transactions of the Ameri-
                           can Fisheries Society 119: 101-111.                                 McFadden, J. T., and E. L. Cooper. 1962. An ecological com-
                       Heggenes, J., A. Brabrand, and S. J. Saltveit. 1991. Microhabitat          parison of six populations of brown trout (Salmo trutta).
                           use by brown trout, Salmo trutta L. and Atlantic salmon,               Transactions of the American Fisheries Society 91:53-62.
                           S. salar L., in a stream: A comparative study of underwa-           Mills, D. 1989. Ecology and management of Atlantic salmon.
                           ter and river bank observations. Journal of Fish Biology               Chapman and Hull, London and New York. 351 pp.
                           38:259-266.                                                         Morantz, D. L., R. K. Sweeney, C. S. Shirvell, and D. A. Lon-
                       Heggenes, J., and T. Traaen. 1988. Downstream migration and                gard. 1987. Selection of microhabitat in summer by juvenile
                           critical water velocities in stream channels for fry of four           Atlantic salmon (Salmo salar). Canadian Journal ofFisheries
                           salmonid species. Journal of Fish Biology 32:717-727.                  and Aquatic Sciences 44:120-129.
                       Hesthagen, T. 1988. Movements of brown trout, Salmo trutta,             Netboy, A. 1974. The salmon: Their fight for survival.
                           andjuvenfle Atlantic salmon, Salmo salar, in a coastal stream          Houghton-Mifflin Company. Boston, Mass. 594 pp.
                           in northern Norway. Journal of Fish Biology 32:639-653.             Newcombe, C. P., and D. D. MacDonald. 1991. Effects of
                       Huntingford, F. A., N. B. Metcalfe, and J. E. Thorpe. 1988.                suspended sediments on aquatic ecosystems. North American
                           Choice of feeding station in Atlantic salmon, Salmo salar,             Journal of Fisheries Management 11: 72-82.







                                            HABrrAT SUrrABiLrry INDEX MODELS: NoNbfflGRAToRy FRESHWATER LiFE STAGES OF ATLANTIC SALMON 17



                      Noffgren, L., and E. Degerman. 1993. Effects of different water               parr in streams. Journal of the Fisheries Research Board of
                          qualities on the early development of Atlantic salmon and                 Canada 36:1408-1412.
                          brown trout exposed in situ. Ambio 22:213-218.                        Symons, P. E. K., and M. Heland. 1978. Stream habitats and
                      Peterson, R. H. 1978. Physical characteristics of Atlantic salmon             behavioral interactions of underyearling and yearling Atlantic
                          spawning gravel in some New Brunswick, Canada, streams.                   salmon (Salmo salar). Journal of the Fisheries Research
                          Canadian Fisheries and Marine Service Technical Report                    Board of Canada 35:175-183.
                          Number 785. iv + 28 pp.                                               Terrell, J. W., T. E. McMahon, P. D. Inskip, R. F. Raleigh, and
                      Peterson, R. H., P. G. Daye, and J. L. Metcalfe. 1980. Inhibition             K. L. Williamson. 1982. Habitat Suitability Index models:
                          of Atlantic salmon (Salmo salar) hatching at low pH. Cana-                Appendix A. Guidelines for riverine and lacustrine applica-
                          than Journal of Fisheries and Aquatic Sciences 37:770-774.                tions of fish HSI models with the Habitat Evaluation Proce-
                      Peterson, R. H., and J. L. Metcalfe. 1979. Responses of Atlantic              dures. U.S. Fish and Wildlife Service FWS/OBS-82/10.A.
                          salmon alevins to temperature gradients. Canadian Journal of              54 pp.
                          Zoology 57:1424-1430.
                      Power, G. 1969. The salmon of Ungava Bay. Arctic Institute of             Thompson, D. 1993. Status of the Atlantic salmon, Salmo
                          North America Technical Report Number 22. Calgary, Al-                    salar L., its distribution and the threats to natural populations.
                          berta. 72 pp.                                                             Pages 303-306 in J.G. Cloud and G.H. Thorgand, editors.
                      Rideout, S. 1989. History of the Atlantic salmon restoration                  Genetic conservation of salmonid fishes. Plenum Press, New
                          program. Pages 1-4 in H. L. Kincaid and J. G. Stanley, edi-               York and London.
                          tors. Atlantic salmon brood stock management and breeding             Thorpe, J. E. 1988. Salmon enhancement: Stock discreetness and
                          handbook. U.S. Fish and Wildlife Service Biological Report                choice of material for stocking. Pages 373-388 in D. Mills
                          89(12).                                                                   and D. Piggins, editors. Atlantic salmon, planning for the
                      Riley, S. C., G. Power, and P. E. Ilissen. 1989. Meristic and                 future. Timber Press, Portland, Oreg.
                          morphometric variation in parr of ouananiche and anadro-              Tremblay, G., F. Caron, R. Verdon, and M. Lessard, 1993. Influ-
                          mous Atlantic salmon from rivers along the north shore of the             ence des parametres hydromorphologiques sur l'utilisation de
                          Gulf of St. Lawrence. Transactions of the American Fisheries              ]'habitat par les juveniles du Saumon atlantique (Salmo
                          Society 118:515-522.                                                      salar). Pages 127-137 in R. J. Gibson and R. E. Cutting,
                      Rimmer, D. M., U. Paim, and R. L. Saunders. 1984. Changes in                  editors. Production ofjuvenile Atlantic salmon, Salmo salar,
                          the selection of microhabitat by juvenile Atlantic salmon                 in natural waters. Canadian Special Publication in Fisheries
                          (Salmo salar) at summer-autumn transition in a small                      and Aquatic Sciences Number 118.
                          river. Canadian Journal of Fisheries and Aquatic Sciences             Trial, J. G. 1989. Testing habitat models for blacknose dace and
                          41:469-475.                                                               Atlantic salmon. Ph.D. thesis, University of Maine, Orono.
                      Sayers, R. E., Jr. 1990. Habitat use patterns of native brook trout           129 pp.
                          and stocked Atlantic salmon: Inter-specific competition and
                          salmon restoration. Ph.D. thesis, University of Maine, Orono.         Trial, J. G., and J. G. Stanley. 1984. Calibrating effects of acidity
                          125 pp.                                                                   on Atlantic salmon for use in habitat suitability models.
                      Schaffer, W. M., and P. F. Elson. 1975. The adaptive significance             Completion Report A-054-ME. Land and Water Resources
                          of variations in life history among local populations of Adan-            Center, University of Maine, Orono. 37 pp.
                          tic salmon in North America. Ecology 56:577-590.                      Trial, J. G., C. S. Wade, and J. G. Stanley. 1984. HSI models for
                      Scott, W. B., and E. J. Crossman. 1973. Freshwater fishes of                  northeastern fishes. Pages 17-56 in J, W. Terrell, editor. Pro-
                          Canada. Bulletin of the Fisheries Research Board of Canada                ceedings of a workshop on fish Habitat Suitability Index
                          Number 184. iv + 996 pp.                                                  models. U.S. Fish and Wildlife Service Biological Report
                      Scruton, D. A., and R. J. Gibson. 1993. The development of                    85(6).
                          habitat suitability curves for juvenile Atlantic salmon (Salmo        U.S. Fish and Wildlife Service. 198 1. Standards for the develop-
                          salar) in riverine habitat in insular Newfoundland, Canada.               mentofHabitat Suitability Index models. 103 ESM. U.S. Fish
                          Pages 149-161 in R. J. Gibson and R. E. Cutting, editors.                 and Wildlife Service, Division of Ecological Services, Wash-
                          Production ofjuvenile Atlantic salmon, Salmo salar, in natu-              ington, D.C. 168 pp.
                          ral waters. Canadian Special Publication in Fisheries and             Warner, K. 1963. Natural spawning success of landlocked
                          Aquatic Sciences Number 118.                                              salmon, Salmo salar. Transactions of the American Fisheries
                      Siginevich, G. P. 1967. Nature of the relationship between in-                Society 92:161-164.
                          crease in size of Baltic salmon fry and the water temperature.        Warner, K., and K. A. Havey. 1985. Life history, ecology and
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                          Board of Canada Translation Series Number 952. 14 pp.                     Maine Department of Inland Fisheries and Wildlife. Augusta.
                      Sigler, J. W., T. C. Bjornn, and F. H. Everest. 1984. Effects of              127 pp.
                          chronic turbidity on density and growth of steelbead and coho
                          salmon. Transactions of the American Fisheries Societ                 Watt, W. D., C. D. Scott, and W. J. White. 1983. Evidence of
                                                                                           y
                          113:142-150.                                                              acidification of some Nova Scotian rivers and its impact on
                      Sosiak, A. J., R. G. Randall, and J. A. McKenzie. 1979. Feeding               Atlantic salmon, Salmo salar. Journal of the Fisheries Re-
                          by hatchery-reared and wild Atlantic salmon (Salmo salar)                 search Board of Canada 40:462-473.







                   18 BIOLOGICAL SaENcE REPORT 3



                   Appendix. Model Evaluation Form

                      The habitat suitability index (HSI) model for juvenile Atlantic salmon is intended for use in the habitat evaluation
                   procedures (HEP) developed by the U.S. Fish and Wildlife Service. This model for nonmigratory freshwater stages of
                   Atlantic salmon is the third generation of a model that was developed originally from a review and synthesis of existing
                   information on Atlantic salmon. The model was modified based on field testing in Maine in 1984 and further evaluated
                   by comparison of alternative model outputs with a long-term data base from Canada and habitat selection data gathered
                   in Maine. Despite the testing of this HSI model, further improvement and revision could result in an even better and
                   more useful model. Please complete this form following application or review of the model. Feel free to include
                   additional information that may be of use to either a model developer or model user. We also would appreciate
                   information on model testing, modification, and application, as well as copies of modified models or test results. Please
                   return this form to


                      Landscape and Habitat Analysis Section
                      National Biological Service
                      Midcontinent Ecological Science Center
                      4512 McMurry Avenue
                      Fort Collins, CO 80525-3400


                   Thank you for your assistance.






                                   HABITAT SurrABILnY INDEX MODELS: NONMIGRATORY FRESHWATER LiFE STAGES OF ATLANTIC SALMON 19



                  Species Atlantic salmon
                  Location
                  Habitat or cover type(s)
                  Baseline- Other
                  Variables measured or evaluated






               I  was the species information useful and accurate?                                         Yes      No
                  If not, what coffections or improvements are needed?





                  Were the variables and curves clearly defined and useful?
                  Yes     No
                  If not, how could they be improved?





                  Were the techniques suggested for collection of field data:
                                   Appropriate?        Yes - No
                                   Clearly defined?    Yes - No
                                   Easily applied?     Yes - No
                  If not, what other data collection techniques are needed?




               1  Were the model equations logical? Yes - No
                                                 Appropriate?        Yes     No
                  How could they be improved?





                  Other suggestions for modification or improvement (attach curves, equations, graphs, or other appropriate
                    information)






                  Additional references or information that should be included in the model:








                  Model evaluator or reviewer                                                      Date
                  Agency
                  Address
                  Telephone Number: Comm:                                  -Fax:








                    A list of current Biological Science Report@ follows:
                      1.   Reproduction'and Distribution of Bald Eagles in.Voyageurs National Park, Minnesota, 1973-1993, by Leland H.
                             Grim and Larry W. Kallemeyn. 1995. 29 pp.
                      2.   Evaluations of Duck Habitat and Estimation-of Duck Population Sizes with a Remote-Sensing-Based Systein,
                             by Lewis A Cowardin, Terry L. Shaffer, and Phillip M. Arnold.. 1995. 26 pp.





















































                   NOTE: The mention of trade names does not conititute endorsement or recommindation for use by the Federal GoXemment.






























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                                                            National Biological Service




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                                                      sibility includes fostering the sound use of our@
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                                                      also has- a'major respons@bifity for American
                                                      Indian reservation communities.












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