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                                     This, manual is the: result of work sponsored by theIationa,[Coastal Resources Research
                                     a,nO'Qevel6pmedt Institute pursuant to NOAA contract    number AQ66.0-5628-0. The
                                     Yiews expTets6d herein 'are those of the -a uthor(s) and do not. necessarily rqfled the View's
                                     of NOAA or'-any of its, sub-agencies: .







                              Construction and Operations

                              Manuel for a Tidal-Powered

                              Upwelling Nursey System


                                         by

                              Robert B. Baldwin
                              Lowcountry Seafood, Inc.
                               McClellanville, S.C.

                                 William Mook
                              Mook Sea Farm, Inc.
                               Damariscotta, ME

                              Nancy H. Hadley
                         Marine Resources Research Institute
                        S.C. Department of Natural Resources


                                Raymond J. Rhodes
                          Office of Fisheries Management
                       S.C. Department of Natural Resources


                                M. Richard DeVoe
                            S.C. Sea Grant Consortium


                  Property of CSC Library

US Department of Commerce
NOAA Coastal Services Center Library
2234 South Hobson Avenue
Charleston, SC 29405-2413









                                                                     TABLE OF CONTENTS



                                        Introduction          ...................................................................... I


                                                   Background
                                                   The Tidal Upweller System
                                                   Site Selection
                                                   Permitting

                                        Construction Requirements for the Upweller                               ............. 7

                                                   Introduction
                                                   Step-by-Step Construction Instructions
                                                   (illustrated)

                                        Operation of the Tidal Upweller                      ................................. 29

                                                   Flow Rates
                                                   Stocking Densities
                                                   Maintenance Requirements
                                                   Thinning and Sorting
                                                   Carrying Capacity
                                                   Labor Requirements

                                        Cost Considerations                ..................................................... 39


                                                   Costs of Materials and Construction
                                                   Operating Costs
                                                   Relative Cost Savings

                                        Literature Cited and Further Reading                          ........................ 43

                                        Acknowledgments                 ......................................................... 44








                                       CONSTRUCTION AND OPERATIONS MANUAL


                                                                   FOR A


                                    TIDAL-POWERED UPWELLING NURSERY SYSTEM




                                    INTRODUCTION


                                    Background

                                    Commercial fishermen in South Carolina and the Southeastern
                                    United States have traditionally varied their fisheries, harvesting
                                    finfish, shrimp, clams and oysters depending on the season and
                                    market. Legislation banning or restricting the use of certain gear
                                    types and designating sea trout and spottail bass as sportfish only
                                    has, in effect, ended the inshore commercial fishery in this region.
                                    The continuing decline in the ex-vessel price of shrimp and the
                                    increase in operating costs of a shrimp boat are forcing many
                                    shrimpers to look for alternatives. Some shrimpers who lost their
                                    boats in Hurricane Hugo are scaling down their operations and
                                    putting more emphasis on the clam and oyster part of their harvest.
                                    A number of fishermen are beginning to diversify their operations
                                    by entering the shellfishing industry, with some interested in
                                    establishing clam or oyster aquaculture- operations.

                                    The potential for shellfish aquaculture in the southeast is promising.
                                    ln general, wild clam populations have been declining for several
                                    years, while market price and, as a result, harvest pressure have been
                                    increasing. As clam populations decrease, less broodstock is left to
                                    reproduce and the downward trend in landings is reinforced. Areas
                                    that have been heavily harvested take years to recover and, because
                                    of constant fishing pressure, may never regain their original
                                    densities.


                                    Aquaculture is being advocated to bolster wild harvests. Hatcheries
                                    are able to produce seed clams at any time and in large quantities.
                                    However, the small seed produced by the hatchery cannot be
                                    planted in the field until it has grown large enough (to 8-10 mm) to
                                    survive (Manzi and Whetstone 198"t). The early nurseries were
                                    simply land-based raceways through which filtered seawater was
                                    pumped. When land-based upwelling systems were developed,

                                        Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System1







                                      more clams were raised in a smaller area (Manzi et al. 1984, Manzi
                                      and Castagna 1989). A typical upweller consists of a piece of plastic
                                      pipe 8" - 24" in diameter with a screen on the bottom. The clams are
                                      placed in the screen and the water flows up through the screen,
                                      passing through the clam mass, and exits through an outlet at the
                                      top. The clams remove food from the water as it passes through.
                                      Most hatcheries use filtered, sterilized water and then raise their own
                                      algae to feed the larval and post-set clams. However, as clams grow
                                      they require more food than is practical to grow, so a land-based
                                      nursery system is dependent upon large volumes of good quality,
                                      food-rich water (Castagna and Kraeuter 1981).

                                      Conventional land-based nursery systems must compete with
                                      residential and commercial uses for expensive waterfront property
                                      Besides the high land cost, conventional land-based nurseries require
                                      pumps and electricity to move the large volumes of water the clams
                                      require, and backup systems in case of mechanical or electrical
                                      failure. If the water quality should change due to pollution or low
                                      salinity, the nursery cannot be easily moved. Although hatchery
                                      seed is relatively inexpensive ($3-5 per 1000), the capital intensive
                                      nature of a land-based nursery makes plantable seed much more
                                      expensive ($20-50 per 1000).

                                      Several alternatives to land-based nurseries are in use in various
                                      southeastern states. In Virginia and North Carolina, bottom
                                      nurseries are sometimes employed. These may consist of trays filled
                                      with sand or other substrate and placed in protected waters.
                                      Alternatively, seed may be broadcast directly on the bottom and
                                      covered with various devices to exclude predators. In Florida,
                                      regulations limit bottom culture to low-profile structures (6 inches
                                      maximum height above substrate). There, soft cages made of nylon
                                      mesh are used as bottom nurseries. In South Carolina, survival of
                                      small seed in bottom plants of these types is poor, due to heavy
                                      mortalities from natural predators and the heavy load of fine silt
                                      which may totally cover the cages in a few days, smothering the
                                      clams. Cages raised slightly off the bottom have been successfully
                                      used, but require continuous, labor-intensive maintenance to control
                                      siltation and fouling. These cages have the additional drawback of
                                      being cumbersome to deploy and harvest. Because flow through
                                      such cages is greatly reduced by the small mesh size needed to retain
                                      seed clams, they can only be stocked at very low densities. Thus a
                                      considerable number of cages and a large bottom area are required to
                                      raise even a modest quantity of 8-10 mm seed.



                                      2 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                     The Tidal Upweller System

                                     One alternative to land-based or bottom nurseries for hard clams is
                                     the tidal-powered upweller nursery system. Such a system has been
                                     designed and successfully tested in Maine (Mook and Johnson 1988).
                                     Both the capital cost and operating cost of such a system are lower
                                     than a land-based system. It does not require expensive land,
                                     pumps, electricity or algae, and it can be moved easily if water
                                     quality or land uses change. A tidal-powered system is significantly
                                     less expensive to construct than a land-based system, but provides
                                     many of the same advantages, including predator protection and
                                     rapid, uniform seed growth. In comparison to a bottom nursery, a
                                     floating system is easier to maintain. Upwelling systems require less

















                                     Fig. 1 -Three-dimensional schematic ot the Tidal-powered Upwelling
                                     Nursery System.

                                     area than bottom trays to maintain the same number of seed. They
                                     can be inspected at any tide and the stocking and harvest of seed is
                                     accomplished by exchanging removal subunits (bins). Such a system
                                     appears to offer a very attractive nursery alternative for shellfish
                                     producers.

                                     The tidal-powered upwelling system described in this manual is
                                     essentially a large tank supported in the center of a floating raft
                                     which doubles as a work platform (Fig. 1). The tank houses
                                     upwelling bins similar to those used in land-based upwelling
                                     nurseries. The floating raft has a large scoop on one end which traps
                                     tidally driven water and directs it into the upwelling tank. The
                                     water rises through the individual bins and exits out through drains
                                     located below the water line. The drains flow into exit troughs

                                          Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 3







                                    which direct the water out the rear of the structure. The entire raft is
                                    moored from the scoop end to a single anchor, which allows the raft
                                    to pivot with the tide so that the scoop always points into the current.

                                    The pilot system which has been built and tested in South Carolina
                                    has the following dimensions:

                                            Raft length:               20 ft
                                            Raft width:                12 ft
                                            Tank length:               16 ft
                                            Tank width:                 4 ft
                                            Tank depth:                38 ft (scoop end); 2 ft (back end)
                                            Scoop dimensions:          Inner: 8 ft w x 30 inches h
                                            Bin dimensions:            19 inches x 19 inches x 18 inches
                                                                       deep
                                            Capacity:                  16 bins
                                            Mooring radius:            100 ft (in 21 ft of water)

                                    Site Selection


                                    As with any aquaculture operation, the most critical decision to be
                                    made in the use of the tidal-powered upweller system is the selection
                                    of an appropriate site. Fortunately, with the tidal system, the
                                    decision is revocable. If a site turns out not to be suitable, the system
                                    can be moved to a new location (assuming permitting restrictions
                                    will allow).

                                    Factors that must be considered in siting the tidal-powered upweller
                                    are water currents, salinity range, depth and width of the creek,
                                    water quality (pollution factors), exposure to wave action, and
                                    potential for navigational interference. State agencies, such as the
                                    Department of Natural Resources in South Carolina, can provide
                                    assistance in determining suitability of potential sites.

                                    Since the upwelling system is powered by tidal currents, it is
                                    imperative to select a site with adequate flow. Based on operation of
                                    the prototype, we believe that an average current of 0.5 knots will be
                                    adequate to operate the system, although faster currents are
                                    desirable. Current speeds will be different for each site and also vary
                                    over the daily tidal cycle as well as on a more seasonal basis. Over a
                                    tidal cycle, the current averages about 0.5 knots if the maximum
                                    current approaches 0.9 knots. Current tables, published annually by
                                    NOAA, are usually available from nautical supply stores which
                                    carry navigational charts. They may also be ordered from:



                                    4 Construction and Operations Manual for aTidal-Powered Upwelling Nursery System







                                                       NOAA Distribution Branch
                                                       6501 Lafayette Ave.
                                                       Riverdale, MD 20737
                                                       (301)436-6990

                                      These tables show time and speed of maximum and minimum
                                      currents for many locations, but will probably not contain your
                                      precise site. However, they will provide an indication of the
                                      likelihood that adequate currents are available in your vicinity The
                                      chapter on Operation of the Upweller contains details on
                                      determining current speeds at a proposed site.

                                      Hard clams require high salinity 1>25 ppt). Occasional short spells of
                                      lower salinity (down to 20 ppt) are only slightly deleterious, but
                                      prolonged salinity below 25 pptwill reduce growth rates, and
                                      frequent or prolonged salinity below 20 ppt may result in mortality.
                                      It is important to know the seasonal salinity variation at your
                                      proposed site, and particularly the salinity changes to be expected in
                                      event of heavy rainfall.

                                      The tidal upweller system, as described, draws 5 to 6 feet of water,
                                      which is obviously the minimum depth required. However, it is
                                      desirable to have several feet between the upweller and the creek
                                      bottom at low tide, particularly if the creek bottom is muddy.
                                      Otherwise the system may be subject to heavy siltation and require
                                      more frequent cleaning. The system is designed to pivot around a
                                      single fixed mooring. The site must allow room for this rotation.

                                      As with any aquaculture operation, water quality is a prime
                                      consideration. Avoid sites which may be impacted by industrial
                                      activities, agricultural runoff, frequent boat traffic, and other
                                      potential sources of contaminants.. State natural resource agencies
                                      can usually assist in identifying the potential for pollution problems
                                      at a proposed site.

                                      The tidal upweller system can tolerate moderate wave action, and in
                                      fact this is one of its advantages, since the wave action reduces silt
                                      accumulation in the system. However, sites which may be exposed
                                      to waves of 1 to 1.5 feet should probably be avoided. The prototype
                                      system was torn from its mooring by wave action in a major storm.

                                      Finally, the tidal upweller must not create a navigational hazard.
                                      Selecting a broad enough creek to moor the upweller is critical.
                                      Ideally, the tidal upweller system should have room to rotate on its
                                      mooring without entering the main channel. The system must be

                                           Construction and Operations manual for a Tidal-Powered Upwelling Nursery System 5






                                  adequately marked with lights to prevent night-time collisions.
                                  Selecting a site which is not subject to heavy boat traffic reduces this
                                  risk.


                                  Permitting

                                  The tidal-powered upweller nursery system is a floating unit and
                                  will likely require a series of federal and state permits prior to
                                  deployment. Contact should be made with the local district office of
                                  the U.S. Army Corps of Engineers and the state coastal zone
                                  management agency and/or fish and game agency for permit
                                  requirements and limitations. Not all states have developed
                                  regulatory frameworks for the use or lease of the water column in
                                  coastal areas; it is therefore recommended that the relevant agencies
                                  be contacted before an investment is made in the purchase,
                                  construction and deployment of the unit.


























                                           i






                                  6 Construction and Operations Manual for aTidal-Powered Upwelling Nursery System









                                    CONSTRUCTION REQUIREME-NTS FOR THE UPWELLER


                                    Introduction


                                    Construction of the tidal-powered upwelling nursery system may
                                    take anywhere from 200 to 250 hours to complete and will require
                                    two persons. However, additional time should be added to this
                                    estimate if the builders are not familiar with floating raft structures.

                                    A variety of wood and hardware will have to be obtained before
                                    construction begins. Table 1 lists the types and quantities of
                                    materials necessary to construct the upweller, along with unit costs
                                    (in early 1994 dollars).

                                    Tools necessary for construction of the tidal upweller include a
                                    power (circular) saw, a 3/8" or 1/2" power drill, hole saw for the
                                    power drill, hammer, pry bar, square, level, tape measure and a paint
                                    brush and roller.


                                    As components of the upweller are constructed and completed, they
                                    should be painted, especially before assembling the components.

                                    Design specifications and a step-by-step account of construction is
                                    presented in the next section.


                                    Step-by-Step Construction Instructions

                                    A. Base Construction


                                    1. Each of the three 22' long 4x4 skids are made by splicing two 12'
                                    4x4s together as shown in Fig. 2a. Use a 2' overlap to make the joint.

                                    2. Place the three skids side by side, mark and notch them as shown
                                    in Fig. 2b, to accommodate the 2' x 6' cross pieces. Each notch will be
                                    about 1.5" deep and 5.75" wide depending on the actual 2" x 6"
                                    dimensions. Note: notches should, starting at one end (which will
                                    be the back of the tank), be centered on 4', 8', 12', 16' and 20'. The
                                    first notch should have its edge coincide with the end of the 4x4 and
                                    the last notch should have its front edge at the 20' mark. Cut a notch
                                    1.5" deep and 3.5" long in the front end of each 4x4 skid to accept the
                                    2' x 4's.



                                         Construction and Ooerations Manual for a Tidal-Powered Upwelling Nursery System 7







                                          Table 1. Type and Cost of Materials Used in the Construction of a
                                          Tidal-Powered Upwelling Nursery for Shellfish in South Carolina*

                                          Quantity                      Materials                    Unit Cost (1994)

                                          10                  2" x 10" x 12'#2TR                     @           11.30
                                            5                 2" x 10" x 10'#2TR                     @            8.44
                                            3                 2" x 10" x 8'#2TR                      @            7.83
                                            8                 2" x 6" x 1242TR                       @            6.33
                                          15                  2" x 4" x 8'#2TR                       @            2.80
                                          12                  2" x 4" x 12'#2TR                      @            3.73
                                            7                 4" x 4" x 1242TR                       @            8.00
                                          34                  5/4" x 6" x 12'TR Decking              @            6.65
                                          12                  3 /4" x 4' x 8' BC ply TR              @           25.19
                                          16                  1/4" x 4' x 8' AC Firply               @           13.57
                                          16                  V x 6" x 10'#lTR                       @            5.20
                                          10                  1" x 6" x 16'#1TR                      @            8.32
                                            4                 1" x 6" x 12'#ITR                      @            6.24
                                          24                  3/8" x 6" galv carriage bolts          @             .50
                                          20                  3/8" x 5" galv lag bolts               @             .40
                                          24                  3/8" x 5" galv hex bolts               @             .50
                                            4                 3 / 8" x 4" galv lag bolts             @             .49
                                            8                 5/16" x Ygalv lag bolts                @             .34
                                            3                 3 / 8" Eye Bolts galv                  @             .76
                                            3                 5" gaiv cleats                         @            1.55
                                            6                 #14 x 3" brass wood screws             @             .50
                                            1 box             20 lb 2" ss nails                      @          121.80
                                            1 box             20 lb 3" ss nails                      @          119.04
                                            1 box             10 lb 3.5" ss nails                    @           60.00
                                            1 box             4 lb 3/4" ss nails                     @           36.00
                                          16 feet             3/4" PVC pipe                          @             .10/ft
                                          20 feet             3" PVC pipe (Schedule 40)              @             .25/ft
                                          16                  3" PVC couplings                       @            1.09
                                            1 pack            monel staples                          @            7.00
                                          40 feet             20 x 30 mesh fiberglass
                                                              window screen                          @         110.00/100'roll
                                            1                 barricade light and batteries          @           22.45
                                          10                  dock floats                            @           49.50
                                            4                 galvanized steel corner brackets       @           11.46
                                            5 gal.            epoxy paint (surplus)                  @            5.00/gal
                                            2 gal.            anti-fouling paint (surplus)           @           15.00/gal
                                          12 feet             1/4" x 1.5" plastic lath               @             .15/ft
                                          40 sq ft (5' wide) I" x 1 " plastic coated wire mesh       @            3.00/ft
                                          45 feet             1/4" nylon line                        @             .25/ft
                                            1 tube            silicone caulking                      @            3.00

                                            Several of these 1994 cost estimates are based upon surplus prices and/or
                                          special discounts. Materials purchased at regular retail prices may be
                                          higher than listed.



                                          8 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                        3. Cut five 2x6s each 49.5" long. Fit the base together with the two
                                        outside 4x4s flush on the outside with the ends of the 2x6 cross
                                        pieces. The middle skid should be centered on the mid-point of each
                                        2x6. To constructthe base for the intake scoop center an 8' 2x6 in the
                                        last 2x6 notch and an 8' 2A in the notches at the end of the 22' skids.
                                        Lay another 2x4 on edge, connecting the front of the 2x6 at the 16'
                                        station with the end of the front 2'x4 (See Fig 20.

                                        Mark the bottom edge of the 2x4 where it crosses the 4x4 skid. When
                                        cut on this line, the angled cut side of the 2x4 will fit against the side
                                        of the skid. Mark the 2x6 and 2x4 cross pieces on the inside edge of
                                        the 2x4 and cut off the ends at that line. The 2x4 is then nailed in
                                        place with the top flush with the top of the 4x4, 2x6, and 2x4. Repeat
                                        the procedure for the opposite side.

                                        4. Nail the base together with 35"ss nails, making sure the skids are
                                        perfectly parallel, and square to the cross pieces.

                                        5. Nail a half sheet of 3/4" plywood onto the base, making sure that
                                        the end is flush with the first 2x6 cross piece (position #0), and
                                        leaving exactly 3/4" from each side of the plywood floor to the
                                        outside edge of the 4x4 skid.

                                        6. Finish the tank floor by butting a full sheet of 3/4" plywood to the
                                        first piece, and a full sheet to the second piece leaving, as before, 3/4
                                        inches along each side. Butt a 2' x 4' piece of 3 /4" plywood to the
                                        last full sheet. Measure and cut 2 triangular pieces of 3/4" plywood
                                        to finish the tank-scoop base. Nail the entire floor to the base with 3"
                                        ss nails.


                                        Fig. 2 -TANK BASE


                                              a) Splice - 4" X 4" (Top View)
















                                             Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System9










                                        Fig. 2b & 2c -TANK BASE



                                            b) Notching - 4" X 4" (Side View)



                                                                            (For 2"x 6")

                                            f*j         I@j         L+J          L*j         LW

                                                                           4'           4'          4'
                                                   4-          4' 41.
                                             0                       2            3           4            5






                                            c) Assembled Tank Base


                                                                                                                     00


                                                                                     4" x 4"











                                                                                                                       2" 4"














                                                                                                          2" x 4"





                                                                  2" x 6"









                                       10 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                                       B. Tank Sides


                                       1. Each tank side is made from two full sheets of 3/4" plywood.

                                       2. Make each tank wall as shown in Fig. 3, by laying the pieces out
                                       flat, end to end, snapping the "cut" line with chalk, and cutting each
                                       section with a circular saw. (The plywood side at the rear (shallow
                                       end) of the tank will measure 2', while the side at the front [deep]
                                       end will measure 38".)


                                       3. Keeping the cut side down, and starting at the rear of the tank, toe
                                       nail each wall section to the tank base (2"ss nails) making sure that
                                       the outside of the wall is flush with the outside of the skids, and that
                                       the inside of the wall is up tight against the plywood floor of the
                                       tank. An 8-foot section of tank side should bridge the spliced section
                                       of the skids.


                                       4. Gently, lift the front (deep) end of the tank onto small blocking,
                                       and then block the rear (shallow) end of the tank even higher so that
                                       the top of the tank sides are level from side to side and lengthwise.
                                       Be sure to support the base in several places along its length. The
                                       level should be checked periodically throughout construction.

                                       C. Scoop Sides

                                       1. Using a piece of 3/4" plywood long enough to reach from the
                                       front edge of the scoop floor to the tank side, bevel the edge to butt
                                       against the front edge of the tank side (Fig. 4).

                                       2. Set the plywood in place against the side of the scoop floor. Mark
                                       the plywood along the bottom of the 2' x 4' side framing of the scoop
                                       floor and cut off the section below the 2' x 4'.


                                       3. Mark the tank edge of the plywood 16" down from the top of the
                                       tank side. Mark the front edge of the plywood 30.5" up from the
                                       scoop floor. Connect the two marks and cut off the top piece. The
                                       remaining piece is the scoop side and can be used as a pattern to cut
                                       out the opposite side. Remember to reverse the bevel on the edge.

                                       4. Nail the scoop sides to the 2' x 4' floor framing. Cut a 2' x 2' to fit
                                       on the inside top edge of each scoop side and nail flush with the top
                                       edge.





                                            Construction and Operations Manual for aTidal-Powered Upwelling Nursery System 11










                                   Fig. 3 -TANK SIDES



                                                                 (3/4" Plywood)


                                                                 16'



                                                8.                             8'


                                                                                                     38"










                                   D. Scoop Top (Ceiling)

                                   1. To construct the scoop top, lay a full sheet of 3/4" plywood
                                   lengthwise across the scoop sides and butt the side against the front
                                   of the tank sides. Making sure the scoop sides are plumb, mark the
                                   plywood top along the outside edge of the scoop sides. Cut along
                                   the lines and nail the plywood top to the 2' x 2' nailers on the scoop
                                   sides (Fig. 5).

                                   2. To finish the scoop top, rip a full sheet of 3/4" plywood in half
                                   lengthwise. Lay the 1/2 sheet against the first sheet mark, cut to fit
                                   and nail to the 2' x 2' nailers. The front edge should be even with the
                                   front edge of the scoop sides.

                                   3. Cut a strip of 3/4" plywood 4" to 6" wide and as long as the joint
                                   in the two pieces of the scoop top and nail over the top of the seam.

                                   4. Cut a 2x4 to fit across the front edge of the scoop top and nail to
                                   the top of the plywood as a stiffener. Cut and nail two more 2x4
                                   stiffeners to the front outside edge of the scoop sides.





                                   12 Construction and Operations Manual for a Tidal-Powered Upwel ling Nursery System









                                               Fig. 4 - RAFT FRAME LAYOUT


                                                                                                                 -E
                                                                                                              x
                                                                                                                 0
                                                                                                                 0           0 0
                                                                                                                             0 0
                                                                                                                              3::2



                                                                                                                 L

                                                        0



                                                        to                                                                              x
                                                        x
                                                                                                                                        04

                                                                  L             U)
                                                                                E
                                                                                                                                   0
                                                                             x  LL                                                 0 W
                                                                             : U)                                                  3::2
                                                                             C,j (1)                                               >@ rn
                                                                                0-

                                                                                            rh





                                                                                                     0

                                                                                    0 4)             x
                                                                                       32
                                                                                       U)
                                                                                            IL I     C',
                                                                  U




                                                         x                              x

                                                         04                             (N




                                                                   L
                                                                                                      cm
                                                        .S                                            2-
                                                        0                                             0
                                                                                                      0
                                                        0
                                                                                                      :tr
                                                        :x                                            x
                                                               I                                      :@r



                                                  Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System      13







                                 E. Tank Hangers

                                 1. Using Fig. 6a as a guide, tack 2x6 hangers to the sides. The
                                 hangers should be plumb, and centered on 4', 8', 12', and 16' from the
                                 back edge of the tank sides. (The back and front hangers are not
                                 centered on the marks, but are flush with the ends of the tank.)

                                 2. Make each hanger long enough so that 6" extends above the tank
                                 side and an inch or so extends below the 4x4 skid. The front edge of
                                 the hanger at position 16' should be beveled at an angle to
                                 accommodate the sides of the intake scoop (see Fig. 4). The hanger
                                 at 20' is located on the scoop side.

                                 3. Drill a 3/8" hole through each hanger and the 4A skid behind it
                                 and bolt the hangers to the skids with 6" x 3/8" galvanized carriage
                                 bolts, nuts, and washers. (The nuts and washers should be on the
                                 inside of the skids.)


                                 4. Firmly nail the plywood sides to the hangers. Be sure to place
                                 extra nails at the wall joints.

                                 5. Notch the top six inches of each hanger (except at the front and
                                 back of the tank) as shown in Fig. 6b. The notches should be
                                 centered on the middle of each hanger, about 1.5" wide, and the
                                 bottoms should be flush with the top of the tank sides.

                                 6. Trim off the bottom of each hanger so it is flush with the bottom of
                                 the 4A skid (see Fig. 6c).

                                 7. Brace off the sides of the tank at the front and back so the sides are
                                 plumb.

                                 F. Raft Framing

                                 1. Find and mark the midpoint of five, 12'2xl0s, then make marks
                                 two feet out from the middle towards each end.


                                 2. Drop each 2x10 into the hanger notches, line up the 2 foot marks
                                 with the inside edge of each tank wall, and nail in place through the
                                 2x6s. The 2xlOs at each end of the tank are nailed to the outside face
                                 of the front and back 2x6 hangers.

                                 3. Drill 3/8" holes through the hangers and 2xlOs and bolt with 3/8"
                                 x 6" galvanized carriage bolts as shown in Fig. 7a. The 2xlOs at each
                                 tank end should be lagged into the hangers with 3/8" x 5" lag screws.

                                 14 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                                             Fig. 5 - INTAKE SCOOP & WEED SCREEN SUPPORTS
                                             Side View: Front of Tank





                                                                            X


                                                                            CCLL
                                                                           CD                  IQ!
                                                                                   +__         6
                                                                                               Cf)





                                               LL                                                                               LU









                                                                                                                0

                                                                                                                       0
                                                                                                                       0
                                                                                                                       U)

                                                                                     IE      8 a

                                                                 U_


                                                                                                                       4M
                                                                                                                       r-
                                                                                                                       cc


                                                                                                                       40
                                                                                                                       x

                                                                                   ...................
                                                                      Go                                 0




                                                                                                        co

                                                                                                      ?I












                                                  Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 15






                                   4. For each of the raft sides, splice two 12'2x10s as shown in Fig. 7b,
                                   with 2x10 backing, or butt blocks at least 3 feet long.

                                   5. Trim 1.5" off the ends of all 2xlO cross frames except for the ones
                                   at the front and back of the tank. Fasten the side frames to the cross
                                   frames (see Fig. 4), nailing into the end grain with 3.5" ss nails and
                                   then adding 3/8" x 4" or 5" lag screws. (Before fastening, make sure
                                   the cross frames are perpendicular to the side framing.)

                                   6. Reinforce each corner with steel corner brackets.


                                   7. Bolt in 4x4 and 4x6 mooring bits to each corner. These should
                                   extend about 8" above the raft decking and be made of oak if
                                   possible (see Fig. 4).

                                   8. Measure and cut 2xI0s to fit between each cross frame, parallel to
                                   the tank. The inside edge of each 2x10 should be on a mark 8" from
                                   the outside of the 3/4" tank wall (see Fig. 4). Nail securely in place
                                   with 3.5" ss nails.


                                   G. Tank Wall Stiffeners


                                   1. Cut and fit 2x4s to go along the top edge of the tank on the
                                   outside of the walls between each pair of 2x6 hangers. Nail these
                                   securely in place as shown in Fig. 8a and 8b, flush with the top edge
                                   of the 3/4" plywood. After building the upweller raft, the exposed
                                   edge of plywood should be carefully sealed or covered to prevent
                                   water damage.

                                   H. Outlet Holes


                                   1. Find and mark the midpoint on the tank wall between each 2xI0
                                   cross frame (except for in the front tank section). These will be the
                                   center marks for lining up the removable bin supports.

                                   2. Find and mark (on the top edge of the tank) the midpoint between
                                   the bin support marks and each adjacent 2x10 cross frame. These
                                   marks are the center marks for each seed bin station.


                                   3. Using a carpenter's square, mark a point on the inside of the tank
                                   wall 7.5" down from each bin station mark.


                                   4. At each of these 16 marks on the tank wall, drill a hole slightly
                                   smaller in diameter than a 3" Schedule 40 PVC coupling (slip x slip).


                                   16 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                     Fig. 6 -TANK HANGARS (2" X 6")



                        a)    4'    4'     4'     4'






                                           4'x 4"









                     b)
                                    Notched for 2" x1 0"
                                    Cross Beams






                                   2" x 6" Hanger






                                         C)



                                                       2" x 6" Hanger







                                4" x 4"
                             fAr
                                A,-r2x










                        Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 17









                Fig. 7 - RAFT FRAMING




                a) 2" x 10" Cross Frame & 2" x 6" Hangars







                                                                       3/8" x 16" Bolt

                                                                       2' From Center
                                                                       To Inside Edge of Plywood





                                                 2" x 6"       3/4"
                                                 Hanger        Plywood
                                                               Wall







                 b) 2" x 10" Raft Side - Splice


                                                                         3' - 2" x 10" Butt Block







                                                                             plice













                 18 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                                              Fig. 8 - TANK TOP STIFFENERS


                                              a) Side View


                                                                                                                     2" x 10"
                                                                                                              '< Cross Frames





                                                                               2" x 4"
                                                                              Tank Top                                  2" x 6"
                                                                              Stiffeners                             Tank Hanger






                                                                                 4" x 41,
                                                                                 Skids





                                              b) Cross Section:





                                                                              2" x 4"
                                                                              Stiffeners__@@



                                                                                                                    Tank
                                                                                                                          Wall








                                                                                                                    4" x 4"
                                                                                                                    Skids
                                                           Li                     Li

                                                   Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 19







                                 Ream each hole until the couplings can be pounded in place with a
                                 block of wood (see Fig. 9).

                                 1. Bin Supports

                                 1. Measure the tank width from the outside of the tank top stiffeners.
                                 This should be 52.5". Cut 4 2x4s to this length.

                                 2. Make a 2.25" long by 2.5" deep notch at each end of the 2x4s. The
                                 bin supports will fit across the tank, so that the top surface will be V
                                 above the top of the tank (Fig. 10).

                                 3. Each of the 2x4 bin supports should be drilled and lagged into the
                                 2x4 tank top stiffeners with 5/16" x 3" lag bolts. These can be
                                 removed as desired, while building the raft.

                                 J. Exit Trough Construction

                                 1. Nail V x 3" spruce (or pine) strapping (ripped from I" x 6") to the
                                 sides of the tank between the 2x6 hangers, with its top edge on a line
                                 marked 10.25" down from the top edge of the tank.

                                 2. Cut four strips of 1/4" plywood, 8" wide x 8'long.

                                 3. Assemble the two trough bottoms as shown in Fig. lla. Nail (with
                                 2" ss nails) a 10' length of strapping to the underside edge of two of
                                 the plywood strips, and complete with a 6' piece of strapping.

                                 4. Nail 1" x 3" strapping to the underside of the 2x10s which run
                                 parallel to the tank. The strapping should be offset 1/4" from the
                                 inside of these 2xl Os so that the trough wall (1 /4" plywood) will be
                                 flush with the inside face of the 2x-10 framing (Fig. 11b).

                                 5. Hold the 16' long trough bottom up along the outside of the tank.
                                 The back end of the trough should be even with the back edge of the
                                 tank. Mark the inside edge of the trough bottom (the edge not
                                 reinforced with strapping) for the 2x6 hangers, and cut out notches
                                 for the hangers so that the 1/4" plywood fits up against the side of the
                                 tank on top of the 1 " x 3 " strapping (Fig. 11 b). Nail the trough bottom
                                 to the top of the strapping.

                                 6. Cut trough sides from 1/4" plywood: four sections, each 11" x 8'.

                                 7. Nail these to the inside edge of the strapping beneath the 2xl0s,
                                 and to the strapping on the underside of the trough bottom (Fig. l1b).

                                 20 Construction and Operations Manual for a Tidal -Powered U pwel I ing Nursery System







                                               Fig. 9 - OUTLET HOLE LOCATION (Side View)


                                                       A-- 2" x 10" Cross Frame            Bl nStation,                  Sin Support
                                                        Ae- 2" x 6" Hanger                    Mldpol,                       Mark


                                                                                   71tv
                                               Top of Tank                             (D
                                                   Wall
                                                                                      Hole For Coupling To Use 3" Pipe.
                                                                                      Put Hole 7112" Below Top of Tank









                                               Fig. 10 - BIN SUPPORTS








                                                                         U U                        U U            A=- 1     Above Tank
                                                 Tank   /
                                                  Top                  2" x 4" Bin Support
                                                Stiffener















                                                    Construction and Operations Manual for aTidal-Powered Upwelling Nursery System 21







                                        Fig. 11 -TROUGH CONSTRUCTION


                                        9) Trough Bottom Layout:




                                                                  8                                   81



                                                                                           11. x3" Strapping
                                                    ......................................     r...................



                                                                       10,                                 6f








                                        b) Trough Cross Section:


                                                                  2" x 10" Cross Frame


                                                                 211 x 4"__.                      kl"x3"

                                                                                   1/4"
                                                                                   plywood






                                                                                                1 " x 3"
                                                                                   1" x 3"
                                                                                     1

















































                                        22 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                       8. Cut off the front end of the trough at a 400 angle, frame the end
                                       with strapping and nail on an end piece (1 /4" plywood) to block off
                                       the front end of each trough.

                                       K. Tank Front and Back Walls


                                       1. For the back wall of the tank, cut out a piece of 3/4" plywood 24"
                                       wide by 52.5" long. Secure this to the 2x6 hangers along each side
                                       with 3.5" ss nails.


                                       2. For the front of the tank, cutout a piece of 3/4" plywood 16" x
                                       52.5" and fasten it with nails and lag screws to the front of the tank.
                                       For both the front and back of the tank the top edge of the plywood
                                       should fit snugly under the front and back 2x10 cross frames.

                                       L. Weed Screen Supports

                                       1. Using a bevel gauge to measure the angle, make a template and
                                       then cut three weed screen supports from 5/4" x 6" (or 2A) stock as
                                       shown in Fig. 5. Nail these securely in place, centered on each skid.
                                       Nail 2 2A uprights to the front cross frame centered over the 4A
                                       studs. Cut a 2x4 72" long for a center longitudinal stiffener for the
                                       intake scoop (Fig. 12 & see Fig. 5).

                                       3. Drill 3/8" holes through the side of each skid and install eye bolts
                                       V from the leading edge of each skid (see Fig. 5).

                                       M. Weed Screen Installation


                                       1. Using hog rings or "J" clips and 1" x 1" vinyl coated lobster trap
                                       wire, fabricate a screen 8' x 3'.

                                       2. Fasten an 8'length of 3/4" PVC pipe to the top and bottom.

                                       3. Holding the screen, centered, on the front of the weed screen
                                       supports, tie a 15 foot length of 1 / 4" nylon line to the pipe at the
                                       bottom of the weed screen at a point corresponding to each of the
                                       three eye bolts.

                                       4. Pass one end of the line through each eye bolt, snugging the pipe
                                       down to the tank skids. When the raft is operating, the line will run
                                       in front of the screen to deck cleats.





                                           Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 23








                                N. Flotation


                                The prototype used 10 22.5" x 48" x 13" plastic dock floats with 480
                                Ibs. of flotation. Other flotation can be used. Whatever flotation
                                material is used, it must be evenly distributed and fastened securely
                                up within the 2xI0 raft framing. The exact location of the raft's
                                waterline is not critical as long as the outlet holes and the discharge
                                troughs are submerged.

                                0. Decking

                                1. The decking materials is 5/4" x 6" pressure treated wood.

                                2. Additional support (2x4s) for decking can be added as needed,
                                depending on type and means of securing flotation.

                                3. Run a length of decking or 2x6 along the length of the tank over
                                each outlet trough.


                                P. Bin Construction


                                1. Figs. 13a and 13b show the top and front view of a bin.

                                2. For 16 bins cut: 32 18" x 19" and 32 18" x '19.5" pieces of 1/4"
                                plywood; and, 64 21" and 64 19.5" pieces of V x 3" strapping.
                                Assemble as shown in Figs. 13a and 13b, using corner brackets to
                                stiffen the corners and 3/4"stainless steel nails to attach the
                                strapping to the plywood.

                                3. Measure the distance between the top and bottom pieces of
                                strapping on the outside of the bin, cut and nail in place V x 6"
                                backing for drilling the outlet holes.

                                4. Mark for the outlet holes, 7.5" down from the center of the top
                                edge, and drill for 3" Schedule 40 PVC pipe. This should be a tight
                                fit.


                                5. Stretch screening over the bottom of each bin, and staple it to the
                                1" x 3" reinforcement. Run a bead of silicone around the bottom
                                edge, and batten down the screening with ripped 5/4" stock about
                                1/4" thick, cut to the appropriate lengths, and 3/4" stainless steel
                                nails.


                                6. Silicone the inside corners of each bin.



                                24 Construction and Operations Manual for a Tidal -Powered Upwel I i ng Nursery System









                                         Fig. 12 - INTAKE SCOOP &WEED SCREEN SUPPORTS
                                         (Top View: Front of Tank)








                                                                                            2" x 10" Front Cross Frame




                                                                      2" x 6"
                                                                      hanger                    00
                                                                                                .0

                                                                                                       Center of Scoop
                                                                                                       Stiffener (2" x 4")




                                                                                                         Weed Screen
                                                                                                 3       Supports (2" x 4")




                                                  j


                                                                      2" x 6"
                                                                      hanger


















                                              Construction and Operations Manual for aTidal-Powered Upwelling Nursery System 25







                                7. Cut 32 strips of 1/4" x 1.5" plastic lath 4" long. Attach two strips
                                per bin onto the I" x 3" strapping on the top-out sides of the bins
                                (Fig. 130. The top of the strip should extend 1.5" above the bin.
                                When the bins are in position, one screw in each strip will secure the
                                bins to the 2xlO cross frames and 2x4 bin supports.

                                Q. Tank Covers

                                1. The upweller tank should be covered to keep out birds, predators,
                                foreign objects and sunlight. Cut four pieces of 1/4" plywood 54"
                                long and wide enough to fit between the 2xlO cross frames.

                                2. Fasten two small wooden blocks for handles (or one could use
                                store-bought handles if preferred) approximately 12" from each end.
                                The covers will slide under the longitudinal boards over the outlet
                                trough and sit on top of the tank hangers.

                                R. Mooring System

                                1. Because of the flat and square surfaces on the upweller, there is
                                significant water resistance when the tides are running. The
                                anchoring system used, either single or multiple, must be solid. The
                                upweller was moored to the mainline of an adjacent rack growout
                                system which uses a home-made steel anchor at each end.

                                S. Navigational Marking

                                1. In most instances, the upweller will have to be equipped with
                                some sort of navigational markers. You should consult with your
                                local U.S. Coast Guard official or state agency representative about
                                the requirements in your location.

                                2. A barricade light (with batteries) may be sufficient for your needs.















                                26 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                                          Fig. 13 - SEED BINS



                                                                                                              1" x 3"
                                                                                                              Strapping
                                                                                                              @ Corners
                                          a) Side Views
                                                                         1" x 3" Strapping


                                                                                             3"
                                                                                             outlet
                                                                                             Holes

                                                                        ........... ..

















                                                                                    21


                                          b) Top View





                                                                                         1/4" Nylon Line
                                                                   1/4" Plywood




                                                                                                                   04





                                                              JL_







                                               6nstruction and Operations Manual for a Tidal-Powered Upwelling Nursery System 27








                                    Fig. 13 (Continued)






                                    c) Bin Hanger Detail (Two different hanging systems)


                                       3/4" PVC @_ 1/4" Plywood                                     1M" Plastic Lath
                                       Dowel               1/4" Nylon
                                                                                      0
                                                           Rope



                                                                                                    V x 3" Strapping
                                        V x 3" Strapping
                                        Notched for
                                        Nylon Rope





                                                                      14          Knots


                                                                           PVC
                                                                           Cover
                                                                           Plate






























                                    28 Construction and Operations Manual for a Tidal-Powered Upwel ling Nursery System








                                     OPERATION OF THE TIDAL UPWELLER


                                     The pilot tidal upweller system was used to grow seed clams from a
                                     size of 1 mm to 6 mm. We believe it can be used to grow larger seed,
                                     but it has not actually been tested for the larger sizes. Nevertheless,
                                     the operating principle is the same as for land-based upwelling
                                     systems. Seed are placed on a fine mesh screen and water rises up
                                     through the seed, bringing food and carrying away wastes. As the
                                     seed grow, they are thinned by dividing them into progressively
                                     more growing bins. As seed usually demonstrate a rather wide
                                     range of growth rates, they are sorted into size classes as they are
                                     thinned.


                                     Flow Rate


                                     The carrying capacity of an upweller system depends on the flow
                                     rate. In a tidal upweller system the flow rate is a function of the
                                     current speed. In addition to being different for every site, current
                                     speed varies throughout the tidal cycle and to a lesser extent from
                                     day to day We have based our carrying capacity determinations on
                                     the flow rate resulting from an average current speed for our site.

                                     Current speed can be estimated by floating a weighted float a known
                                     distance. A suitable float can be made by embedding a heavy nail in
                                     the flatter end of a wine bottle cork. Test the float before using. It
                                     should float vertically with more than half of the cork below the
                                     water line. If it floats too low, it will be hard to see. If it floats too
                                     high it will be unstable and subject to influence by wind and waves,
                                     thus affecting the calculations.

                                     Current should be measured on a still day to minimize wind
                                     interference with the float. Carefully place the float in the water at
                                     one end of the upweller raft. Time how long the cork requires to
                                     float the length of the raft and retrieve it at the far end with a dipnet
                                     or something similar. Repeat this process at least three times in rapid
                                     succession and average the times. Calculate the current speed in ft/
                                     sec. For example, if the float moves 20 feet in 10 seconds, the current
                                     speed is 2.0 ft/sec (20 divided by 10).

                                     In order to determine the average current, you could measure
                                     currents at intervals for an entire day (or more) and calculate the
                                     average. Fortunately, the average current can be reasonably
                                     estimated if the maximum current is known. If a tidal current table
                                     is available, it will provide an estimate of the time maximum current
                                     will occur in your general vicinity

                                         Construction and Operations Manual for a Tidal-Powered Upwel ling Nursery System 29







                                       If a current table is not available, several current measurements will
                                       be needed in order to estimate the timing of the maximum current.
                                       Refer to a tide chart to determine time of high or low tide. Begin
                                       taking measurements three hours before or after high tide. Every 30
                                       minutes (more frequently if possible), take another measurement. If
                                       the second and third measurements are lower than the first, you
                                       started your measuring too late. Begin on another day, starting 4-5
                                       hours before or 1-2 hours after high tide. Record the times and
                                       current speeds carefully Ideally, your measured speeds will increase
                                       and then decrease, allowing you to determine the magnitude and
                                       timing of the maximum current. You can then return on subsequent
                                       days at the appropriate time (relative to the tide) and take additional
                                       measurements to better estimate the maximum current.


                                       For example, assume you arrive on site at 1:00 pm on a day when
                                       high tide occurs at 4:00 pm. You take the following series of
                                       measurements:


                                       Time               Distance                     Seconds            Speed

                                       1:00 pm            20 ft                        20 sec             1.0 ft/s
                                       1:20 pm            20 ft                        15 sec             1.3 ft/s
                                       1:55 pm            20 ft                        10 sec             2.0 ft/s
                                       2:15 pm            20 ft                        12 sec             1.7 ft/s
                                       2:30 pm            20 ft                        16 sec             1.2 ft/s

                                       The maximum current was 2.0 ft/sec and occurred approximately 2
                                       hours prior to high tide. On future days, you can measure the
                                       current only once, 2 hours before the tide. Measure the maximum
                                       currents on several days representing average tides for your area.
                                       Average these measurements to determine your average maximum
                                       current speed.

                                       Once you have a good estimate of the maximum current speed, it is
                                       easy to calculate the average current. The average current is
                                       approximated by this equation:

                                                          average current = 2/pi X maximum current

                                       For convenience, we have tabulated average currents expected from
                                       maximum currents in the range of 1 to 6 ft/sec in Table 2. This table
                                       also shows the flow rate through the upweller bins which is expected
                                       to result from various currents. These flow rates were determined in
                                       our pilot system and each system may vary in performance.
                                       However, our flows seem to correlate fairly closely with those

                                       30 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                            reported by Mook for a system in Maine under a different current
                                            regime (Mook and Johnson 1988). Therefore, we think most upweller
                                            systems will generate flow rates similar to those shown in the table.

                                            Actual flow rates through the upweller system can be measured by
                                            floating the cork in the outflow trough. However, the narrow width
                                            of the trough makes this method difficult, as the cork may frequently
                                            collide with the trough wall. Mook described a method of measuring
                                            the flow with a liquid dye Wook and Johnson 1988; they used
                                            evaporated milk).

                                            The dye is injected below the water surface using a small diameter
                                            straw. Its passage over a known distance can then be timed. The
                                            current speed (in ft/sec) must be converted into flow volume by
                                            measuring the width and depth of the water column at the point of
                                            measurement. An example calculation is given in Table 3.



                                            Table 2. Average current speed based on various maximum current
                                            speeds and predicted flow rates through the upwelling bins

                                            Maximum Current               Average Current            Predicted Flow Rate

                                            (ft/s) (cm/s)      (knot)   (ft/s)  (cm/s)    (knot)     (liters/n-dn) (gal/min)

                                            1          30      0.59     0.64       19      0.38            28          7.4
                                            1.5        45      0.89     0.95       29      0.57            35          9.2
                                            2          60      1.19     1.27       38      0.75            42       11.1
                                            2.5        76      1.48     1.59       48      0.94            49       12.9
                                            3          91      1.78     1.91       58      1.13            56       14.8
                                            3.5        97      1.90     2.04       62      1.21            59       15.6
                                            4        121       2.37     2.55       77      1.51            71       18.7
                                            4.5      128       2.49     2.67       81      1.59            74       19.5
                                            5        152       2.96     3.18       97      1.89            85       22.4
                                            5.5      167       3.26     3.50       106     2.08            92       24.3
                                            6        182       3.56     3.82       116     2.26            100      26.4












                                                 Construction and Operations Manual for aTidal-Powered Upwelling Nursery System 31








                                 Table 3. Calculating flow rate through the bins

                                 Steps: 1. Measure current in outflow trough
                                         2. Determine volumetric flow through outflow trough
                                         3. Divide by number of bins upstream

                                 Example:

                                         Given:
                                                 8 bins operating upstream
                                                 Current speed in trough: 24 in. in 4 sec. = 6 in. /sec.
                                                 Trough width: 8 inches
                                                 Water depth in trough: 6 inches

                                         Multiply the width by the depth by the distance traveled:

                                                 8 x 6 x 6 = 288 cubic inches/second

                                         Convert to gallons/ second (231 cubic inches = 1 gallon):

                                                 288 divided by 231 = 1.25 gallons/second

                                         Convert to gallons/minute:

                                                 1.25 x 60 = 75 gallons/minute

                                         Divide by the number of bins:

                                                 75 / 8 = about 9 gallons / minute per bin

                                 The procedure is the same, and the calculation is easier, if you use
                                 the metric system. Make your measurements in centimeters. A
                                 cubic centimeter = a milliliter and there are 1000 milliliters in a liter.


                                         Given:
                                                 trough is 20 centimeters wide
                                                 water is 15 centimeters deep
                                                 speed is 15 centimeters/sec

                                 Flow = 20 x 15 x 15 = 4500 cubic centimeters/sec = 4.5 liters/sec
                                 270 liters/minute

                                 Flow/bin = 270/8 = about 34 liters/min (= about 9 gallons/min)


                                 32 Construction and Operations Manual for a Tidal-Powered Upwclling Nursery System






                                            Stocking Densities

                                            Once the flow rate through the system is known, appropriate
                                            stocking densities for various seed sizes can be determined. Table 4
                                            (column 2) shows the desired flow rate per unit volume of various
                                            sized seed clams. To determine stocking volumes, divide your
                                            average flow rate in liters per minute by the desired flow ratio from
                                            column 2 of Table 4. The result is the number of liters of clams which
                                            can be stocked in one bin. For example, Table 4 shows that I mm.
                                            clams require 180 liters of water for each liter of clams. If your
                                            average flow is 60 liters per minute, each bin can be stocked with
                                            0.333 liters (60 divided by 180) of 1 mm clams. In practice you
                                            would probably round this amount down to 300 ml or up to 350 ml.
                                            The flow ratios shown in Table 4 were determined in our pilot
                                            system. They may be used as starting points for initial operation but,
                                            due to site differences (e.g., food quality and quantity, turbidity,
                                            salinity), each upweller system will have different optimum stocking
                                            densities. Therefore, be prepared to adjust stocking densities
                                            depending on your own experiences.



                                            Table 4. Recommended flow ratios (liters of water per liter of
                                            clams per minute) and stocking densities for various size seed
                                            clams in the tidal upwelling system.

                                            Seed Size     Flow ratio       Stocking Volume (n-d) at Average Flow G/m):
                                            (mm)                           30        40        50        60        70       80


                                            1                    180       167       222       278       333       389      444
                                            2                    120       250       300       416       500       583      667
                                            3                    100       300       400       500       600       700      800
                                            4                    60        500       667       833     1000      1167       1333
                                            5                    45        667       889       1111    1333      1556       1778
                                            6                    35        857      1143       1429    1714      2000       2286
                                            7                    27        1111     1482       1852    2222      2593       2963
                                            8                    18        1667     2222       2778    3333      2889       4444
                                            9                    12        2500     3333       4167    5000      5833       6667


                                            Note: the flow ratio is the same if using US measurements (e.g.,
                                            gallons) but make sure that water flow and clams are measured in
                                            the same unit, i.e., both in gallons, both in quarts, or both in ounces,
                                            etc.







                                                 Construction and Operations Manual for a Tidat-Powered Upwelling Nursery System 33






                                Stocking volumes in Table 4 are packed volumes. To determine packed
                                volume of a sample of clams, half-fill a graduated container with
                                water. This can be a graduated cylinder (most accurate) or a graduated
                                beaker or pitcher. The container should be translucent. Pour the seed
                                clams slowly into the container using a funnel. (Always work over a
                                pan or tray in case you spill some seed). When all the seed are in the
                                container, add additional water if necessary to cover the seed with at
                                least an inch of water. Tap the side of the container several times to
                                settle ("pack") the clams. The height of the column of clams after
                                settling is the "packed volume."

                                Maintenance Requirements

                                Once the tidal upweller is deployed and stocked with seed, routine
                                maintenance is required to ensure optimum growth and survival. The
                                frequency of maintenance will depend on the growth rate of the clams
                                and the fouling rate. Both of these are temperature and salinity
                                dependent. The higher the temperature and the salinity, the faster the
                                seed will grow and the faster the system will foul. In the winter,
                                thorough cleaning may only be needed monthly, while in the summer
                                it will be required at least biweekly.

                                The system and the clams should be inspected weekly (biweekly is
                                probably adequate in winter). Remove the bins from the tank and
                                rinse the clams to remove all silt and feces. Examine the seed for
                                fouling organisms (e.g., sea squirts) and predators (small crabs).
                                Examine the screens for fouling by bryozoans or algae which will
                                retard flow. Rinse the clams into one corner of the bin and lay the bin
                                on its side to allow the screen to air dry. Air drying the bins once a
                                week will retard fouling on the screen. (Exercise caution not to let very
                                small seed dry out or get overheated during this process.)

                                When screens become fouled, or sea squirts or other nuisance species
                                are found in the bins, it is time for a thorough cleaning. This will be at
                                least biweekly during summer, possibly only monthly when it is
                                cooler. The clams should be removed from the bins. Each bin and
                                drain pipe should be scraped to remove any barnacles and oysters.
                                The screen should be scrubbed with a nylon brush. Both screen and
                                bin may be sprayed with dilute chlorine bleach, rinsed and allowed to
                                air dry. (It is convenient to sort and thin the clams at this time, since
                                they are already out of the bins. This process is described in the next
                                section.)

                                The weed screen will need to be cleaned as frequently as the bins. It
                                should be pulled up, scrubbed with bleach and air-dried. While the

                                34 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                        bins are out of the tank, a push-broom, hoe or similar tool is used to
                                        stir up the silt in the bottom of the tank, allowing it to be washed out.

                                        Thinning and Sorting

                                        In order to maintain rapid growth, the seed clams must be thinned
                                        regularly. A rule of thumb in land-based nurseries is to thin whenever
                                        the volume doubles. During the growing season, this may be weekly
                                        In the pilot tidal upweller, biweekly thinning appeared to be adequate
                                        to maintain rapid growth even though seed volume often tripled or
                                        quadrupled over two weeks. (This may indicate that the bins could be
                                        stocked more densely if you were willing to clean more frequently.)

                                        Growth is usually improved if similar-sized clams are kept together.
                                        This is accomplished at the sarrietime as thinning by sieving the seed
                                        through a series of screens. Sieves may be purchased in a range of
                                        standard sizes or constructed by attaching various screening materials
                                        to a wooden frame. Table 5 shows seed sizes that are retained on
                                        standard sieves. If you choose to construct your own sieves, you will
                                        need screening materials of varying pore size from 1-1.5 mm up to
                                        about 6 mm. Ideally, you would have four sieves of approximately
                                        1.5, 3,4, and 6 mm. This wouldenable you to sort seed into size
                                        classes of approximately:52 mm, 2-4 mm, 4-6 mm, 6-8 mm, and >8
                                        n1m.


                                        To thin and sort the seed, remove a bin from the upwelling system and
                                        rinse its entire contents into a shallow tray (e.g., a dishpan). If there is
                                        more than one bin containing seed of a given size, they may be
                                        combined prior to sieving. Depending on the size of the seed (and
                                        previous sieving) they should be sieved on one or more screens. Each
                                        sieving will produce two size classes, those which stay on the sieve
                                        and those which pass through. Clams which will stay on the largest
                                        sieve (= 8 mm or more) are ready for transfer to your growout system.
                                        Sieve the clams in water by gently agitating the screen up and down.
                                        Sieving is most effective if relatively small quantities are placed on the
                                        screen at a time.


                                        Determine the packed volume of each size category created by sieving.
                                        If desired, you may also determine the approximate number by
                                        measuring out a small volume of seed and counting them, and/or the
                                        average size by measuring a handful of clams with calipers. If you are
                                        using standard sieves, the number and size of clams in each category
                                        will be fairly close to those listed in Table 5. After sorting, the clams
                                        should be redistributed into clean bins at reduced densities, using
                                        Table 4 to determine appropriate densities. If there is only a small

                                            Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 35






                                   quantity of seed in any one category, they may be combined with the
                                   next category. For example, it would not be economical to maintain
                                   300 ml of 6 mm seed in a separate bin, so these could be combined
                                   with either 5 mm or 7 mm seed.



                                   Table 5. Size and count of seed clams retained on standard sieves


                                         Sieve Size               Seed Size                 Seed Count
                                   US#              mm          (Length,mm)                    (#/ml)

                                   25               0.710             1                         2700
                                   18               1.0               1.5                        800
                                   14               1.4               2                          350
                                   12               1.7               2.5                        200
                                   10               2                 3                          100
                                   8                2.36              3.5                         60
                                   7                2.8               4                           40
                                   6                3.35              5                           20
                                   5                4.0               6                           12
                                   4                4.75              7                             8
                                   31/2             5.6               8                             5
                                   1/4 in           6.3               9                            3.5



                                   Carrying Capacity

                                   The upweller system can accommodate far more 1 mm seed than
                                   could be reared to 8-10 mm in size. The carrying capacity is
                                   determined by the quantity the system can accommodate at an
                                   intermediate size, 1-2 mm less than the final desired size. If the
                                   target size is 10 mm, the carrying capacity is the quantity of 7-8 mm
                                   seed that can be accommodated. These seed will begin to reach the
                                   target size over the next month and therefore the density will be
                                   continually reduced thereafter as seed are moved to the growout
                                   system.

                                   Table 6 shows the number of seed the pilot system can accommodate
                                   by size up to 9 mm. Remember that the system has not actually been
                                   tested with seed larger than 6 mm. The number of 7-8 mm seed
                                   which can be accommodated is about 250,000. This is the carrying
                                   capacity if the target size is 10 mm. If the target size is only 7 mm,
                                   the carrying capacity is considerably higher (about 350,000).
                                   Carrying capacity will be different for each system, depending on


                                   36 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System






                                               factors such as flow rate and ambient food availability.

                                               Labor Requirements

                                               One of the benefits of the tidal-powered upwelling system is its ease
                                               of maintenance. Cleaning is less frequent and takes less time than in
                                               land-based nursery systems. Most of the maintenance and operation
                                               tasks of the tidal system can be accomplished by one operator,
                                               although it will certainly be easier and faster with two.

                                               Routine cleaning of the units, which includes rinsing all the bins,
                                               requires about 45 minutes. A thorough cleaning, including removing
                                               the clams, scrubbing the bins, cleaning the weed screen and
                                               redistributing seed back into the bins, requires approximately 3
                                               hours. Thus, total labor requirements are only about 7.5 hours/
                                               month during the growing season. Of course, these estimates do not
                                               include the time to travel to and from the site.



                                               Table 6. Suggested stocking volumes for 19x19 bins with an
                                               average flow of 52 liters per minute

                                                Seed Size      Seed Count      Volume@er bin           per bin        Syste Lcapacity
                                               (Length,mm)         (#/Ml)            (rnl)           (X 1000)             (X 1000)

                                               1                     2700              300             810                  12,960
                                               1.5                   800               350             280                  4,480
                                               2                     350               450             157                  2,520
                                               2.5                   200               475               95                 1,520
                                               3                     100               520               52                     '832
                                               3.5                     60              650               39                     624
                                               4                       40              850               34                     544
                                               5                       20            1150                23                     368
                                               6                       12            150CI               18                     288
                                               7                         8           200CI               16                     256
                                               8                         5           3000                15                     240
                                               9                         3.5         400CI               14                     224













                                                    Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 37








                                   COST CONSIDERATIONS


                                   Costs of Materials and Construction


                                   The types and costs of materials are listed in Table 1 (see page 8
                                   The total cost of materials in Table 1 is about $ 2,775.00. This does
                                   not include the time to actually construct and launch the upweller.
                                   Someone with carpentry skills, the proper tools, and a part-time
                                   helper should be able to construct and launch one upweller by
                                   "investing" about 240 man-hours G.e., about six weeks of
                                   construction, working at 40 hours per week). Someone with no
                                   carpentry skills may require much more time; the cost of contracting
                                   and/or hiring someone to construct the upweller may need to be
                                   considered.


                                   Operating Costs

                                   The time and frequency for cleaning the upweller's bins and culling
                                   and splitting seed clams are given in the previous section "Operation
                                   of the Tidal Upweller." In addition, it may be necessary to haul the
                                   upweller out of the water, depending upon fouling and other factors
                                   (e.g., storm-related damage repairs) every 12 to 18 months for
                                   scraping, recaulking, painting and other routine maintenance
                                   activities. In general, one should plan to spend about 220 hours
                                   (about 28 days) each year on operating the upweller (e.g., cleaning
                                   bins) and maintenance (e.g., repairing bins and the raft). This time
                                   estimate does not include travel time to and from the upweller site.
                                   Cost of materials for minor repairs and annual maintenance could
                                   range from $100 to $200 each year.

                                   Relative Cost Savings of Using the Tidal-Powered Upwelling
                                   Nursery

                                   The amount of time and cost saved by using the upweller system
                                   will depend on a number of factors, including how much one values
                                   time (economists call this the "opportunity cost of labor and
                                   management" - that is, what other type of income would one forego
                                   to construct, operate and maintain the upweller), the market price
                                   and the size (e.g., 6 mm. vs. 12 mm) of plantable clams one would
                                   normally use for final growout, the amount of time and expense to
                                   construct the upweller, and travel time to and from a suitable site.
                                   A comparative cost analysis of this upweller to other clam nursery
                                   systems has been made (see Baldwin, et al. 1994). Including the cost
                                   of construction labor, it appears that a tidal-powered upweller can be

                                      Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 39






                                     $800 to nearly $1,600 less expensive to construct than small-scale
                                     nursery systems with similar capacity. Including the costs of
                                     construction, the relative annual operating cost savings for the tidal-
                                     powered upweller could exceed $3,000 per year compared to two
                                     other land-based systems (Table 7). In other words, given the
                                     assumptions made in Baldwin et al. 1994, it appears that the cost
                                     savings from using the upweller could "pay back" the initial
                                     construction costs in at least two years. Indeed , the five-year net
                                     present cost savings for the upweller would range from about
                                     $13,000 to $14,700. In contrast, some will prefer backyard land-based
                                     nursery systems like raceways because of ease of access to the
                                     system and the convenience of securing and monitoring the system.






































                                     40 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System








                                      Table 7. Cost comparison of a tidal-powered upweller (TPU) to land-based
                                      nursery systems (URS = upweller-raceway; RS = raceway) with access to
                                      suitable land sites.


                                                                                        TPU           URS             RS*


                                      Initial Construction Cost:                       $4,500        $6,100        $5,300



                                      Projected Annual Operating Costs:

                                      Annual seed purchases:       $3.30/1,000          2,200         2,200          4,690
                                                Operating and Maintenance Labor"        2,180         3,400          1,450
                                                Utilities                                 000         1,800          1,600
                                                Materials for Maintenance                 100           300           200


                                      Total Operating Costs Including Seed:             4,480         7,700          7,940


                                      Projected Annual Operating Savings:"*             N/A           3,220          3,460

                                      Discount Rate:                                    7.0%          7.0%           9.0%


                                      Projected 5-year Present Value Cost:           ($22,574)     ($37,254)     ($35,741)


                                      Projected Savings of the Upweller:                           $14,679        $13,166


                                      *Approximately 533,000 seed clams (2-4 mm) purchased at $8.80 / 1,000
                                      including shipping costs.
                                      **Estimated opportunity cost of the owner-operator's labor only
                                      ***Projected annual operating savings for using the TPU compared to a URS
                                      or RS.





















                                           Construction and Operations Manual for aTidal-Powered Upwelling Nursery System 41







                                           LITERATURE CITED AND FURTHER READING


                                 Baldwin, R.B., N.H. Hadley, R.J. Rhodes and M.R. DeVoe. 1994.
                                         Demonstration and evaluation of the performance of a tidal-
                                         powered upwelling nursery system in South Carolina. Final
                                         report submitted to the NOAA National Coastal Resources
                                         Research and Development Institute, Portland, Oregon. 26pp.

                                 Hayes, J.C. 1981. Forced upwellin.g nurseries for oysters and clams
                                         using impounded water systems. pp. 73-82 in Claus et al.,
                                         eds. Nursery Culturing of Bivalve Molluscs. Eur. Mar. Soc.
                                         Spec. Pub. #7. Belgium.

                                 Hadley, N.H. 1995. A manual for the culture of the hard clam
                                         Mercenaria spp. in South Carolina. S.C. Sea Grant Consortium.
                                         Charleston.


                                 Kemp, F.S. 1991. Clam gardening: a manual for small-scale clam
                                         operations in North Carolina. NOAA, NMFS, Office of Sea
                                         Grant, UNC-SG-91-02. 35 pp. [$5.00 from UNC Sea Grant
                                         College Program.]

                                 Malinowski, S. 1988. Variable growth rates of seed clams in an
                                         upflow nursery system and the economics of culling slow
                                         growing animals. J. Shellf. Res. 7(3):359-366.

                                 Manzi, J. and M. Castagna, eds. 1989. Clam Mariculture in North
                                         America. Elsevier, New York.


                                 Manzi, J., N. Hadley, C. Battey, R. Haggerty, R. Hamilton and M.
                                         Carter. 1984. Culture of the northern hard clam in a
                                         commercial-scale, upflownursery system. J. Shellf. Res.
                                         4(2):119-124.


                                 Mook, W. 1988. Guide to construction of a tidal upweller. Mook Sea
                                         Farm, Inc. Damariscotta, Maine. 23pp.

                                 Mook, W. and A.C. Johnson. 1988. Utilization of low-cost, tidal-
                                         powered floating nurseries to rear bivalve seed. Mook Sea
                                         Farm, Inc. Damariscotta, Maine. 28pp.







                                     Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System 43








                                                      ACKNOWLEDGMENTS


                                 This work was sponsored by the National Coastal Resources
                                 Research and Development Institute, NOAA, U.S. Department of
                                 Commerce through the S.C. Sea Grant Consortium under Contract
                                 No. AQ66.90-5628-03.

                                 The authors wish to express their appreciation to the staff of NCRI
                                 for their assistance and guidance during the course of this project,
                                 and especially to Dr. Earle Buckley and Dr. Steve Olson.

                                 Special thanks go to the Cape Romain Wildlife Refuge (U.S. Fish and
                                 Wildlife Service, U.S. Department of the Interior) and Refuge
                                 Manager George Garris for allowing this project to be conducted
                                 within its boundaries.











































                                 44 Construction and Operations Manual for a Tidal-Powered Upwelling Nursery System




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