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INVESTIGATION OF A WEIR DESIGN ALTERNATIVE FOR COASTAL FISHERIES BENEFITS BARTON D. ROGERS, M.S. WILLIAM H. HERKE, PH.D. E. ERIC KNUDSEN, M.S, FUNDED BY UNITED STATES ARMY CORPS OF ENGINEERS LOUISIANA DEPARTMENT OF NATURAL RESOURCES LOUISIANA STATE UNIVERSITY AGRICULTURAL CENTER LOUISIANA STATE UNIVERSITY COASTAL FISHERIES INSTITUTE UNITED STATES FISH AND WILDLIFE SERVICE LOUISIANA COOPERATIVE FISH AND WILDLIFE RESEARCH UNIT SCHOOL OF FORESTRY, WILDLIFE, AND FISHERIES SH LOUISIANA STATE UNIVERSITY AGRICULTURAL CENTER 365 BATON ROUGE, LOUISIANA 70803-6202 .L8 R64 FEBRUARY 1987 1987 This public document was published at a total cost of $312.62. 150 copies of this document were published in the first printing at a cost of $181.37. The total of all printings of this document, including reprints is $312.62. This document was published by the Department of Natural Resources, P.O. Box 44487, Baton Rouge, Louisiana 70804, to inform the public about Coastal Zone Management under the authority of Public Law 92-583 and La. R.S. 49:213. This material was printed in accordance with the standards for printing by state agencies established pursuant to La. R.S. 43:31. 'ACKNOWLEDGMENTS This study was a success due to the hard work, sacrifice, and perseverance of the field crew: Ms. Cora Cash and Messrs. Ralph Allemand (Field Supervisor), Marc Fugler, and William Sanderson. Data had to be collected every day and 2/7ths of the data were collected on weekends. This study was funded by five institutions: the U. S. Army Corps of Engineers (Agreement No. 14-16-0009-86-1817), the Louisiana Department of Natural Resources (Contract No. 21910-86-10), the Louisiana State University Coastal Fisheries Institute, the Louisiana State University Agri-cultural Center, and the United States Fish and Wildlife Service. Dr. James Geaghan provided statistical consultation for the data analysis. Ms. Dawn Brady provided great assistance in the administration of this project. The study area and logistical assistance were provided by the Sabine National Wildlife Refuge of the U. S. Fish and Wildlife Service. The field facilities were constructed under a previous project that was funded by the U. S. Soil Conservation Service. They also were instrumental in developing the study concept by providing much needed technical input. The Louisiana-Department of Wildlife and Fisheries assisted in the computerized reading of the water level gauge tapes. The Cotton-Miami Corporation graciously allowed us to use their launch ramp and to cross their land in order to access our study site. This was of great Assistance, because otherwise we would have had to go through Calcasieu Lake on a daily basis. Figures 1, and 3 were prepared by Ms. Michelle LaGory. Appreciation is extended to the following reviewers: Mr. Thomas Schultz, Mr. Richard Hartman, Mr. Don Moore, Dr. Gil Bane, Mr. Darryl Clark, Mr. Fred Dunham, and the Environmental Branch of the New Orleans District, U. S. Army Corps of En gineers. U.S. DEPAIRTMP,11 0@ ('0P,!VER('F NIOAP. 2 2 N 11 r 0 b 3 fte"tty Of coc UbraW TABLE OF CONTENTS PAGE ACKNOWLEDGMENTS ................................................... i LIST OF TABLES .................................................... iii LIST OF FIGURES ................................................... iv ABSTRACT .......................................................... v INTRODUCTION ...................................................... 1 METHODS AND PROCEDURE ............................................. 4 Trap ............................................................ 4 Trawling ........................................................ 11 Data Analysis .................................................... 11 RESULTS AND DISCUSSION ............................................ 13 Brown Shrimp .................................................... 13 Brown Shrimp Conclusions ..................................... 21 Species Composition ............................................. 22 Species Composition Conclusions .............................. 26 Environmental ................................................... 28 Salinity ..................................................... 28 Water Level .................................................. 31 Water Temperature ............................................ 34 Environmental Conclusions .................................... 34 GENERAL DISCUSSION ................................................ 36 CONCLUSIONS ....................................................... 42 LITERATURE CITED .................................................. 44 APPENDIX .......................................................... 47 Tables ....................................................... 47 Figures ...................................................... 53 LIST OF TABLES TABLES PAGE 1. Trap catch, biomass, and percent change for both experimental ponds .......................................... 14 2. Mean weight in grams, and percent change, of an individual organism taken by the traps ...................... 17 3. Number and biomass taken by both trawls in the three ponds ................................................. 20 4. Mean weight (grams) of organisms derived from the combined catch from both trawls for the duration of the study ................................................ 27 5. Summary statistics for the daily physical measurements for the experimental ponds (at the levee station) and Grand Bayou; and physical data collected while trawling in the three ponds .......................................... 33 6. Catch of abundant, or economically-important, organisms taken by Herke et al. (1987b)(15 February 1983 through 30 July 1983) and this study (15 February 1986 through 30 July 1986) ............................................... 38 LIST OF FIGURES FIGURE PAGE 1. Grand Bayou study area showing the paired ponds and the trawling station in the control pond ..................... 5 2. Diagram of the paired ponds showing the trawling stations (WE, WB, EE, and EB), the Grand Bayou salinity stations (A and B), and the levee salinity stations in each pond ...... 6 3. Diagram of the experimental-ponds trapping system showing the location of the standard and slotted weirs and the environmental stations ....................................... 7 4. Sketch of the slotted weir as viewed from the end of the chute ........................................................ 9 5. Number, biomass, and mean weight of brown shrimp taken by the traps in each pond ....................................... 16 6. Number, biomass, and mean weight of brown shrimp taken by the trawls in each pond ...................................... 19 7. Number of species, total number of individuals, and biomass of all emigrating species taken by the trap in each experimental pond .................................... 24 8. Number of species, total number of individuals, and biomass of all emigrating species taken by the trawls in each experimental pond .................................... 25 9. Daily salinity readings taken at the environmental and levee stations, and the mean salinity taken at the trawling stations, for both experimental ponds ............... 29 10. Salinity in both ponds (as measured at the levee stations) and in Grand Bayou (average of stations A and B) ............. 30 11. Water level for the experimental ponds and Grand Bayou ....... 32 12. Brown shrimp catch for 1983 and 1984 (Herke et al. 1987b) and 1986 (this study) at the experimental ponds .............. 39 iv ABSTRACT Standard fixed-crest weirs have been demonstrated to reduce fish and crustacean emigrations from the marsh nursery area back toward the Gulf of Mexico. These weirs are continuing to be constructed for wildlife habitat enhancement. The effect of weirs on emergent vegetation is unclear although some research has suggested that emergent marsh vegetation in water-logged soils may experience reduced growth. The objective of this study was to determine whether modification of a standard fixed-crest weir would result in greater export of fishery organisms from the area controlled by the weir. Total catch of emigrating organisms was taken from two nearly identical marsh ponds by traps with a mesh opening of 0.203 inch. Both ponds had a standard fixed-crest weir at the only entrance/exit, with one weir having a vertical slot from top to bottom. Data were collected from 15 February through 30 July 1986, which encompassed the majority of the brown shrimp (Penaeus aztecus) marsh nursery cycle. Salinity, water temperature, and water levels were measured in both ponds and in the nearby waters. Trawling was conducted in these experimental ponds and in a nearby control pond, which had no water-control structure. Over 241% more brown shrimp (84% in biomass) emigrated from the pond with the slotted weir than from the pond with the standard weir. Both the standard and slotted weir were suspected of delaying immi- gration and emigration for brown shrimp. The slotted weir apparently yields median results between the control pond (early and abundant immigration, early emigration, low mean size, and high rate of cycling) and the standard weir (later and less abundant immigration, delayed emigration, increasing greater mean size, and low rate of cycling). For all species combined, over 60% more organisms (62% in biomass) emigrated from the slotted-weir pond for the study period. For the time period studied, the salinities and water levels were generally similar. Water levels in the slotted-weir pond had slightly greater range and standard deviation, however the water level in the slotted weir pond did not drop nearly as low as the water levels outside the experimental ponds. Compared to a standard fixed-crest weir, a slotted weir would provide enhanced fishery access and utilization. The slotted and standard weirs should be evaluated for their effect on emergent vegetation, water levels, salinities, and wildlife and fishery organisms other than brown shrimp. v INTRODUCTION Standard fixed-crest weirs have been implicated in affecting the movements and abundance of many estuarine organisms (Herke 1968, 1971, 1979; Wengert 1972; Herke et al. 1984a, 1985, 1987a,b). Most of the economically-important species that spawn nearshore and migrate into the marsh nursery areas have been either less abundant in.these semi-impounded areas (those affected by we4rs) (Wengert 1972, Herke et al. 1987a) or the fisheries export from the nursery area was reduced (Herke et al. 1987b). Perry (1981) concluded that weirs did not prohib- it brown shrimp (Penaeus aztecus) from entering the marsh because he found shrimp behind a weir; however, he had no control (non-weired).area for comparison. Thus, he was unable to determine whether brown shrimp movement and abundance was reduced by the weir. Several other studies documented shrimp behind weirs, but these have only been a measure of standing crop and did not considered the turnover rate (cycling in and out). The productivity of an area can not be based on standing crop alone, but must consider the cycling of organisms. Two areas may have equal standing crops, but one could have many times the productivity, if the turnover rate is greater. The actual behavioral mechanisms by which water-control structures affect the movement of organisms are not kncwn. One likely mechanism is the reduction in water exchange. Herke et al. (1984b) and Schultz (1985) demonstrated that most of the organisms move with the current. Bradshaw (1985) found significantly lower densities of postlarval and juvenile brown shrimp in a semi-impounded area as compared to an adja- cent non-weired area. Thus, the reduction in water exchange may reduce the number of the young larval and juvenile immigrants. Another possi- ble mechanism is the creation of an ethological barrier by weirs (Herke 1979). That is, the organisms could physically cross the weir but behavioral traits prevented their crossing. Another likely mechanism is the blocking by weirs of a specific portion of the water column at which certain organisms would prefer to migrate; e.g., Herke et al. (1984a) suggested that weirs may impede the movement of juvenile spotted sea- trout (Cynoscion nebulosus) entering the marsh because they migrate at the middle and lower portions of the water column. King (1971), Herke et al. (1984b, 1987b), Rogers and Herke (1985a,b), and Schultz (1985) 2 present data on the vertical migration levels of many organisms. Weirs have been used for many purposes, in Louisiana they have been traditionally used to enhance the habitat for waterfowl and furbearers (Chabreck and Hoffpauir 1965; Chabreck 1968). Weirs maintain a minimum water level and sometimes reduce turbidity, thereby stimulating the growth of widgeongrass, Ruppia maritima, and other submerged aquatic vegetation, important food plants for waterfowl (Wicker et al. 1983). The effects of weirs on other types of vegetation have not been well studied. Weirs are installed to reduce marsh erosion, although we know of no documented evidence that they are effective for this purpose in brackish or saline marshes. Mendelssohn and Seneca (1980) and Mendelssohn et al. (1980) have demonstrated that saltmarsh cordgrass, Spartina alterniflora, has lower levels of standing crop and growth when the drainage is impaired or the plants are in waterlogged soils. These authors attribute decreased growth to increased anaerobic metabolism and subsequent increases in waste products of anaerobic metabolism, e.g. sulfides. Perhaps the longer inundation period caused by the weirs may be detrimental to saltmeadow cordgrass, Spartina patens, as well. At this point, not nearly enough is known about the short or long term effects of weirs on the marsh and the emergent vegetation. Perhaps better structures can be designed that will perform basi- cally the same marsh management functions as those of fixed-crest weirs, while allowing greater fishery organism usage and movement. Such structures may greatly improve fishery resources, while maintaining or enhancing benefits to other wildlife (especially when considering the questionable effects of weirs on emergent vegetation). The objectives of this study were to; 1) compare the catches of fishery organisms emigrating from two marsh ponds, one having a standard fixed-crest weir and the other having the same weir structure but mod- ified to include a 4-inch vertical slot from top to the bottom of the channel, and 2) monitor water level, salinity, and water temperature in each pond. Although several structures were discussed as possible test designs, the vertically-slotted, fixed-crest weir was chosen due to the ease of design and construction., lower cost, and the allowance of move- ment of organisms throughout the entire water column. When applied in marsh management, this slotted design would improve fisheries access with minimal active structural management and would allow easy closing of the slot, if necessary. 4 METHODS AND PROCEDURES Trap This study utilized two marsh ponds that were located in the East Cove portion of the Sabine National Wildlife Refuge in the Grand Bayou watershed, Cameron Parish, Louisiana (Fig. 1). These ponds were also used by Herke et al. (1987b). The ponds were constructed in October 1982 by surrounding a portion of a single natural marsh pond with a ring levee and installing a cross levee, such that the natural pond was divided into two 87-acre experimental ponds (Fig. 2). Each pond enclosed about 65 acres of water and 22 acres of predominantly Spartina patens marsh. These two ponds will be collectively referred to as the experimental ponds. The control pond (Fig. 2) had no water-control structure and was used only for trawl sampling (to be presented later). A single wooden chute, constructed of plywood and pilings, installed in each pond levee, was the only entrance/exit channel for tidal ex- change and aquatic organisms (Fig. 3). These chutes were 6 feet wide, 8 feet deep and 40 feet long. The bottom of each chute was about 4 feet below average water level. Identical trap systems were installed in each chute (Fig. 3). Each trap was 6 feet tall, 6 feet long, and 2 feet wide, and was constructed of welded aluminum alloy covered with monel, market-grade, wire cloth, having 0.047-inch diameter wire and 0.203-inch openings. The end of the trap facing the pond had a V-shaped mouth with a 2-inch vertical slit to funnel emigrating organisms into the trap. A similar mouth with a 3/4-inch vertical slit was placed in the middle of the trap to allow smaller organisms to retreat to the rear of the trap (Fig. 3). This was done to segregate the larger blue crabs (Callinectes apidus) from the smaller organisms, which hampered the crabs from mutilating or consuming the smaller organisms. Deflecting screens, made of the same mesh as that of the traps, were installed to guide immigrat- ing organisms toward a 3-inch (7.62 cm) slot at the pondward edge of the chute and deflecting screens (Fig. 3). This 3-inch slot had a deflector placed on the pon dward side to guide outgoing organisms past this slot. The deflecting screens also guided emigrating organisms into the trap. Thus, immigrants were easily guided into the ponds but all emigrants too large to pass through the mesh were trapped. A complete history of the various water-control structures used at CMD we i !@j VI CY ng N@ EXPERIMENTAL 1,0P PONDS CONTROL POND L 0 2 3 km V,@a -11 Figure 1. Grand Bayou study area showing the paireId ponds and the trawl stations in the control pond. N A 7? Area Enlarged WE in Figure 3 STANDARD-WEIR POND B WB EE LEVEE STATIONS EB SLOTTED-WEIR POND 0 0 ry Figure 2. Diagram of the paired ponds showing the trawling station s (WE, WB, EE, and EB), the Grand Bayou salinity stations@(A and B), and the levee salinity stations in each pond. STANDARD To POND WEIR 11-0 ENVIRONMENTAL STATION CHUTE SLOTTED WEIR LK RAMP r2- TRAP DEFLECTING SCREENS '0 0 0 76-cm wide VERTICAL SLIT RAMP ENVIRONMENTAL STATION Figure 3. Diagram of the experimental-ponds trapping system showing the location of the standard and slotted weirs and the environmental stations. 8 these experimental ponds by Herke et al. (1987b) and during this study is as follows: Pond Dates East West 12 Feb 1983 - 13 Feb 1984 weir no weir 13 Feb 1984 - 20 Apr 1985 no weir weir 20 Apr 1985 - 24 Aug 1985 no weir no weir 24 Aug 1985 - 22 Nov 1985 no weir weir 22 Nov 1985 - 20 Dec 1985 no weir no weir 20 Dec 1985 - present slotted-weir weir On 22 November 1985 the weir on the west pond was removed, to allow both ponds to be open (no structure), with the idea to let the ponds equilibrate in terms of salinity, water level, and fishery organisms. On 20 December 1985, a standard, fixed-crest weir (referred to as the standard weir) was installed on the Grand Bayou side of the trap in the west pond chute (Figs. 2 and 3). The crest of this weir was set 6 inches below average marsh soil level and had a length of 65 inches. On the same date, a standard fixed-crest weir with a 4-inch vertical slot (referred to as the slotted weir) was placed in the chute for the east pond. This vertical slot stopped 3 inches from the bottom, because a 3- X 6-inch timber was used for support across the bottom (Fig. 4). The 3.5- X 3.5-inch vertical timbers and the interior stoplog guides reduced the crest of the slotted weir to 61 inches (Fig. 4). Thus the slot width comprised 6.5% of the weir crest length, i.e., 1 inch of slot per 15.2 inches of weir crest length. The weir crest length was longer than normally used in practice (e.g. 1 foot of weir crest per 70 acres of semi-impounded marsh) because 6-foot wide chutes were necessary for installation of the traps and deflecting screens. Fish, shrimp, and crabs migrating into the ponds, after negotiating either weir, could either pass through the mesh of the deflecting screens and trap, or through the 3-inch wide vertical slot at the pondward end of the deflecting screens (Fig. 3). Incoming organisms too large for this opening were excluded; however, most were small enough to gain access. All organisms too large to pass through the mesh were captured when emigrating from each pond. The traps fished continuously 9 naslil LEVEL STOPLOG->t J. <--GUIDES 14CHUTE FLOOR Figure 4. Sketch of the slotted weir as viewed from the end of the chute. The 61-inch weir crest was set at 6 inches below average marsh soil level. The 4-inch slot went from the weir crest to within 3 inches from the floor of the chute. The bottom stoplog was one continuous timber to provide support for the interior stoplog guides. 10 and were emptied between 0800 and WOO hours dail from 15 February 1986 through 30 July 1986 (including holidays and weekends). A drop screen, of identical mesh as the traps, was lowered in front of each trap to prevent passage of organisms while the trap was being emptied. The entire catch was placed in ice until processing. The catch for each trap was sorted by species. Several species were further sorted into categories as follows; Blue crab (Callinectes saDidus) small blue crab (less than 25 mm; i.e., not easily sexed) immature female crab mature female crab male crab Ladyfi@_h (Elops saurus) leptocephalus juvenile Speckled worm eel (MVro-_)his punctatus) leptocephallis Juvenile/adult The total number of individuals and total weight (in grams) taken each (lay were determined for each speci@2s or other category, as de- scribed above; these data were then codecl onto a personal computer in the field lab. Excessively large catches of a species were subsampled by a method described by Herke (1978). Wl-i-n the entire sample was too large to be sorted, subsampling was don@i iit the total catch Level before sorting to species). The subsamole weight and the remainder weight for both techniques were used to estimate the number of each species in the entire ratch. The pond trap daLa were total catches of all organisms retained by the trap and deflectin@,,-screen mesh while emigrating from each P(Ind, thus the total catches were a census of the popualtions. Therefcre, to test the hypothesis "catches of emigrating organisms from the two ponds were equal" required no statistics, because the catches were the statistical (and biological) populations, not samples of the populations. [Most fishery research projects sample once a week or so (at best), and must use statistics to account for the lack of data between sample dates, but this study took complete data from all dates.] Thus, we did not have to estimate data or derive confidence limits because we took the entire populations from each experimental pond. Daily salinity and water temperature readings were taken at the environmental and levee stations for each pond (Fig. 2 and 3). Daily readings at the levee stations and stations A and B in Grand Bayou were taken with a Beckman RS-5-3 meter, and at the environmental stations with a Hydrolab 8000. (Grand Bayou salin4ty data collection began on 4 April 1986.) The Hydrolabs also recorded salinity and water temperature once per hour from 17 January 1986 through 30 July 1986. Daily water level readings were taken at the chutes in both ponds and in Grand Bayou. (Grand Bayou water level data collection began on 4 March 1986.) A Leupold-Stevens tide gauge, located at the environmental stations, recorded hourly water level readings in each pond. Trawling Trawling was conducted every two weeks from 6 March 1986 through 30 July 1986. Two trawling stations were located in each experimental pond and in the control pond (Figs. 1 and 2). The control pond was a natural area not affected by any water-control structure. The stations. were located in each of the three ponds such that two locations were sampled, one near the entrance (e.g., CE - Control Entrance) and another near the back (e.g., WB - West Back) of each pond. Each station was sampled with a 16-foot and a 6-foot trawl. The 16-foot trawl had 5/8-inch bar mesh in the body and 1/4-inch bar mesh in the cod end, and was towed for 5 minutes (approximate distance of 1/4 mile) with 75-foot ropes from an airboat. The 6-foot trawl had 5/16-inch bar mesh in the body and 3/16-inch bar mesh in the cod end, and was pushed in front of the airboat for 5 minutes (approximate distance of 1/4 mile) along the shoreline as described by Rogers (1985). Trawl samples were processed in the same manner as the trap samples. Salinity and water temperature were measured before each trawl haul with the Beckman instrument. Data Analysis This study was designed to encompass, as much as practical, the seasonal presence of brown shrimp in the marsh. The marsh nursery cycles of the many other important species were not entirely covered by 12 the study. Consequently discussions for these species are presented in much less detail than for brown shrimp, which was the target species of this study. To compare the total catch between the two ponds, percent change in catch and biomass of organisms emigrating from the slotted-weir pond as compared to the same from the standard-weir pond was calculated as follows: where Percent Change = ((SLW/STW)-I) X 100 SLW = total catch or biomass taken in the slotted-weir pond STW = total catch or biomass taken in the standard-weir pond This formula essentially sets the catch in the standard-weir pond to 100%. For example, a percent change of 50 would indicate an increase in catch of 50% from the slotted-weir pond compared to the standard-weir pond, referred to as a 50 percent Increase. A percent change of -50 would indicate a 50% decrease in catch from the slotted-weir pond compared to the standard-weir pond, referred to as a 50 percent decrease. For most graphic and tabular presentation, the trawl data were combined (trawls and stations) for each pond by date.. Brown shrimp trawl catch was analyzed by analysis of variance with a split-plot (split on gear) arrangement of treatments (PROC GLM, SAS 1985). Pond, location (entrance or back), and date were the main effects and date was further examined by its linear (D), quadratic (D*D), and cubic (D*D*D) components. 13 RESULTS AND DISCUSSION Brown Shrimp Since the fishery data were collected for only 5.5 months (15 February 1986 - 30 July 1986), total comparison of the function of the two structures for all species is impossible, because some of the species had not completed their yearly cycling in and out of the marsh nursery. The structures were installed on 20 December 1985 (2 months before sampling began), thus the fishery data collected should reflect what happened during the study period, there being little influence of the initial installation of the structures. Of the most recreationally and commercially important species, some gulf menhaden and Atlantic croaker individuals may have entered the pond before the structures were installed (Rogers and Herke 1985a). Brown shrimp would have begun the marsh part of their life cycle after the structures were installed, and would have basically finished the majority of the marsh part of their life cycle before the study ended (Rogers and Herke 1985a). The trap data revealed that brown shrimp catches from the slotted weir pond were 241% greater in numbers and 84% greater in biomass than from the standard-weir pond (Table 1). This increased catch from the slotted-weir pond was consistent throughout the study (Fig. 5). Brown shrimp emigration began about 3 weeks earlier in the slotted-weir pond (Fig. 5) and appears to be related to the lunar or tidal phases as noted by (Herke et al. 1987b). The mean weight of brown shrimp at.emigration was consistently greater in the standard-weir pond over time (Fig. 5) and when all shrimp weights were averaged (Table 2). Brown shrimp trawling data contributed additional information. Analysis of variance (PROC GLM, SAS 1985) using a split-plot (split on gear) arrangement of treatments was conducted (Appendix Table 1). The analysis indicated a highly significant difference due to the pond main effect (P < 0.01) but, significant interactions with date [particularly for the quadratic (P < 0.0001) and cubic (P < 0.0248) components] precludes a simple interpretation about the pond catch differences. Essentially, the catch in the three ponds varied differently in relation to one another over time. Even though the control pond was more 14 Table 1. Trap catch, biomass, and percent change for both experimental ponds. NUMBER BIOMASS (G) ------------------------------ I ------------------------------- SPECIES STANDARD SLOTTED PERCENT STANDARD SLOTTED PERCENT WEIR WEIR CHANGE WEIR WEIR CHANGE grass shrimp 270,907 388,977 44 133,995 141,183 5 gulf menhaden 219,279 279,171 27 297,798 207,805 -30 brown shrimp 28,681 97,694 241 244,536 449,176 84 Atlantic croaker 22,193 34,176 54 236,704 170,484 -28 white mullet 15,902 21,773 37 167,052 109,461 -34 inland silverside 13,451 36,766 173 15,144 30,441 101 immature female crab 9,018 28,364 215 318,847 504,321 58 male blue crab 8,689 24,874 186 672,912 1,152,386 71 gulf killifish 6,350 11,988 89 28,880 51,509 78 diamond.killifish 4,327 3,890 -10 2,032 1,600 -21 spot 4,045 15,805 291 32,784 49,471 51 striped mullet 3,560 12,921 263 38,391 666,024 1635 sheepshead minnow 3,540 7,464 ill 4,917 10,501 114 sailfin molly 3,165 1,495 -53 3,750 1,868 -50 naked goby 1,859 2,071 11 1,187 1,388 17 bay anchovy 1,614 1,970 22 2,395 2,202 -8 darter goby 1,116 2,223 99 1,075 1,899 77 pinfish 529 6,115 1056 8,717 63,663 630 blue crab (less than 25 mm) 472 6,576 1293 274 2,594 846 mature fem ale crab 421 349 -17 74,419 60,483 -19 white shrimp 368 2,2Z2 504 552 8,886 1511 rainwater killifish Z74 1,013 270 196 685 250 speckled worm eel 115 72 -37 1,267 821 -35 blackcheek tonguefish 112 300 168 1,417 2,660 88 bayou killifish 108 83 -23 130 106 -18 bay whiff 76 532 600 911 4,902 438 mosquitofish 70 38 -46 34 22 -37 clown goby 58 41 -29 63 35 -45 mud crab 43 25 -42 7 6 -9 ladyfish 38 49 @q 432 224 -48 sharptail goby 30 390 1200 515 5,666 1000 sand seatrout 18 37 106 484 759 57 southern flounder 13 115 785 5,636 14,976 166 black drum 5 5 0 23 26 17 rough silverside 5 1 -80 9 1 -85 redea sunfish 4 6 50 36 44 25 longnose killifish 3 2 -33 46 7 -86 sheepshead 3 4 33 57 14 -74 red drum 2 18 800 225 3,953 1660 least puffer 2 49 2350 2 82 3627 15 Table 1. continued. NUMBER BIOMASS (G) ------------------------------ -------------------------------- SPECIES STANDARD SLOTTED PERCENT STANDARD SLOTTED PERCENT WEIR WEIR CHANGE WEIR WEIR CHANGE violet goby 2 1 -50 255 76 -70 Atlantic cu@lassfish 2 1 -50 228 61 -73 green goby 2 9 350 1 3 93 threadfin shad 1 1 0 4 2 -39 fiddler crab 1 2 spotted seatrout 2 21 silver perch 3 15 Atlantic midshipman 1 3 crevalle jack 1 2 hardhead catfish 7 1,389 leatherjacket 2 1 inshore lizard fish 1 55 bluefish 3 2 gizzard shad 5 46 snapping shrimp 1 2 Atlantic spadefish 1 17 bluegill 1 5 pipefish 21 26 squid .3 79 worm eel leptocephalus 2 40 fat sleeper 1 5 620,473 989,731 60 2,298,341 3,724,187 62 1 Percent change is calculated by ((slotted-weir catch standard-weir catch) - 1) x 100. 7,000- 6,000- 5,000- M 4,000- 3,000 z 2,000 1,000 0- 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30jUL 30,0001 Ln 20,000@ 0 10,000- M 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 12, r 8- LIJ z 4, LIJ 0, 51EB 02MAP 17MAR 01APR 16APR-01MA@ 16MAY 31MA@ 15AH 30JUl SJU 7OR, L DATE SET POND -------- SLOTTED WEIR STANDARD WEIR ,/V-1111 Figure 5. Number, biomass, and mean weight of brown shrimp taken by the traps in each pond. 17 Table 2 . Mean weight in gram-, and percent change, of an individual organism taken by the traps. Values are computed for those species that had a total catch of 50 or greater in each experimental pond. SPECIES STANDARD SLOTTED PERCENT WEIR WEIR CHANGE mature female crab 176.8 173.3 -2 southern flounder 130.2 striped mullet 10.8 51.5 378 male blue crab 77.4 46.3 -40 immature female crab 35.4 17.8 -50 sharptail goby 14.5 speckled worm eel 11.0 11.4 3 pinfish 16.5 10.4 -37 bay whiff 12.0 9.2 -23 blackcheek tonguefish 12.7 8.9 -30 Atlantic croaker 10.7 5.0 -53 white mullet 10.5 5.0 -52 brown shrimp 8.5 4.6 -46 gulf killifish 4.5 4.3 -6 white shrimp 1.5 4.0 167 spot 8.1 3.1 -61 sheepshead minnow 1.4 1.4 1 bayou killifish 1.2 1.3 6 sailfin molly 1.2 1.2 5 bay anchovy 1.5 1.1 -25 darter goby 1.0 0.9 -11 inland silverside 1.1 0.8 -26 gulf menhaden 1.4 0.7 -45 rainwater killifish 0.7 0.7 -5 naked goby 0.6 0.7 5 diamond killifish 0.5 0.4 -12 blue crab (less than Z5 mm) 0.6 0.4 -32 grass shrimp 0.5 0.4 -27 mosquitofish 0.5 clown goby 1.1 I Values in this column are rounded from calculations carried to Lliree decimal places. 18 distant from the Gulf, the brown shrimp appeared earlier and in greater abundance in the control pond than in the two experimental ponds (Fig. 6). The control pond was not affected by water-control structures, suggesting that the two experimental structures delayed and reduced recruitment and subsequent standing crops. Even though trap catch from the slotted-weir pond was 2.4 times that from the standard-weir pond, the standing stock trawl estimates for the two experimen'tal ponds were similar in numbers (Fig. 6). This clearly illustrates what was pointed out in the Introduction: two areas may have equal standing stock, yet one may have much higher productivity if its turnover rate is faster. The standing stock biomass was greatest in the standard-weir pond in the latter part of the study (Fig. 6). This was mainly due to the larger shrimp in the standard-weir pond, and was probably a result of delayed emigration from that pond, as noted by Herke et al. (1987b). The biomass peaked earliest in the control pond, again indicating that both structures delayed immigration. The mean weight of brown shrimp from trawl catches was highest and had the greatest increase with time in the standard-weir pond, was intermediate for the slotted-weir pond, mean weight was the lowest and had the least increase with time in the control pond (Fig. 6). Trap catch in the slotted-weir pond was 241% higher than in the standard-weir pond (Table 1); standing crops in the two ponds were similar (Fig. 6) and total trawl catch in the slotted-weir pond was only 32% greater than in the standard-weir pond (Table 3). The only logical conclusion is that brown shrimp were cycling in and out of the slotted-weir pond in less time than the standard-weir pond. Therefore, the greater mean weight and greater increase with time in the standard-weir pond must have been due primarily to a greater delay in emigration from that pond. This resulted in older, and thus larger, shrimp being caught. This conclusion agrees well with a brown shrimp mark and recapture study conducted by Herke et al. (1987b), who reported that brown shrimp were delayed by two weeks on the average from leaving a pond with a weir as compared to a pond with no water-control structure. The measures of standing crop in numbers (Fig. 6) were considerably higher from the control pond, whereas the mean shrimp weight taken in the control pond 1,000- A 800, /A 600 M Z) 400' z 200, 0. 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 1 15 0 0'ir 1,000 (A 0 500' M U I 11@FFP n?MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30ML 115- 10 - z 5, 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JU-N 15JUL 30JUL DATE POND CONTROL ----- SLOTTED WEIR STANDARD WEIR Figure 6. Number, biomass, and mean weight of brown shrimp taken by the trawls in each pond. 20 Table 3. Number and biomass taken by both trawls in the three ponds. ------------ NUMBER ------------ ----------- BIOMASS ---------- SPECIES STANDARD SLOTTED CONTROL STANDARD SLOTTED CONTROL WEIR WEIR WEIR WEIR grass shrimp 29,583 53,898 18,247 4,083 8,788 3,727 gulf menhaden 6,444 10,389 51,047 3,560 6,428 23,494 inland silverside 5,753 6,489 4,509 4,355 4,090 2,860 spot 1,005 2,590 8,026 4,465 6,999 13,078 white shrimp 440 1,341 2,596 1,192 2,153 Atlantic croaker 919 1,193 1,190 5,229 3,978 3,311 brown shrimp 879 1,162 4,050 5,615 3,688 3,881 pinfish 477 665 249 4,498 5,277 2,085 bay anchovy 837 641 5,821 750 553 1,931 rainwater killifish 160 521 736 81 235 349 striped mullet 548 312 201 813 2,058 2,163 immature female crab 136 197 35 1,959 1,962 667 male blue crab 146 181 36 5,090 3,235 1,250 naked goby 183 157 38 107 55 20 gulf killifish 20 45 14 62 145 59 sheepshead minnow 31 42 26 25 41 36 diamond killifish 46 27 1 18 13 1 clown goby 20 25 1 21 24 1 darter goby 16 22 5 13 7 3 blue crab (lesss than 25 mm) 23 20 32 9 10 9 ladyfish 9 13 2 28 6 92 sailfin molly 77 12 16 45 13 11 white mullet 22 7 21 84 81 200 southern flounder 6 20 292 119 mud crab 5 23 1 11 mosquitofish 6 3 7 3 i 1 blackchee-k tonguefish 3 1 33 11 least puffer 2 5 8 10 spotted seatrout, 1 1 2 43 21 3 bay whiff 1 1 1 1 pipefish 16 1 9 18 1 8 ladyfish leptocephalus 4 1 69 0 0 7 sand seatrout 17 100 red drum 2 81 silver perch 2 19 black drum 2 532 crevalle jack 11 44 hardhead catfish 2 31 leatherjacket 3 3 inshore lizard fish 3 186 threadfin shad 5 20 gizzard shad 1 18 pigfish 1 1 scaled sardine 1 1 diamondback terrapin 1 1 45 471 chain pipefish 2 9 redear sunfish 2 10 20 88 green goby 1 1 sharptail goby 1 1 rough silverside 28 62 TOTAL 47,805 80,072 97,128 42,232 50,199 62,504 72 21 (Fig. 6) was less than from either experimental pond. Therefore, brown shrimp must have cycled in and out of the control pond in the least time, while being retained longer by the slotted weir, and longest by the standard weir. This would explain the apparent discrepancy between the higher standing biomass in the standard-weir pond, but the lowest emigration, and subsequent contribution to the fishery, from that pond. It is difficult to determine, from this study and others in the literature, which of these three regimes would be the best for maximization of brown shrimp production. We hypothesize that a higher abundance of smaller shrimp would be better for the resource than a considerably lower abundance of larger shrimp for several reasons * First, the greater numbers would allow brown shrimp to more fully utilize the environmental conditions that they may encounter following. the marsh part of their life cycle. For example, if only a few large shrimp survive to return to the bays and offshore, and conditions are unfavorable, the total number (and biomass) surviving would be lower. Second, if more small shrimp leave the marsh, they have the potential to grow in size and.produce several times the total biomass of the fewer larger ones. Third, the total biomass of numerous smaller shrimp leaving the slotted-weir pond was greater than the total biomass of larger but fewer shrimp leaving the adjacent standard-weir pond as seen in Table 1. Thus, there was relatively high survival and high biomass produced by the slotted-weir pond to*continue growth and possibly provide a greater harvest. Brown Shrimp Conclusions 1. The slotted weir allowed more individuals (241% more) and biomass (84% more) of brown shrimp to emigrate back towards the Gulf than did the standard weir. 2. Brown shrimp emigrated from the standard-weir pond later, and at a larger size, than from the slotted-weir pond. 3. Recruitment into the nursery and emigration were delayed and reduced by both structures, but more so by the standard weir. 22 4. Both structures reduced the cycling of brown shrimp in and out of the marsh nursery with the standard weir reducing it more. 5. Use of a slotted weir should result in more brown shrimp production than would use of a standard weir. Species Composition The interpretation for this section will only consider the time frame of this study (15 Feb ruary 1986 through 30 July 1986). Except for brown shrimp, this study did not cover the entire marsh portion of the life cycle of most of the species. To provide an indication of relative abundance and biomass of the species to each other, catch and biomass for all trawling and trapping combined are listed in Appendix Table 2, which also lists the common and scientific names for all organisms taken in the study. Appendix Figs. 1 - 29 contain the daily trap and periodic trawl catch, biomass, and mean weight for gulf menhaden, Atlantic croaker, spot, southern flounder, striped mullet, white mullet, grass shrimp, inland silverside, gulf killifish, sheepshead minnow, bay anchovy, blue crab (less than 25 mm), immature female blue crab, male blue crab, and mature female blue crab. There was an overall increase of 60% in numbers of all species combined trapped while emigrating from the slotted-weir pond as compared to the standard-weir pond (Table 1). Of the species taken in enough abundance to*make conclusions, the small blue crabs had the greatest increase in abundance (1293%), with pinfish having the second greatest increase (1056%). Brown shrimp, immature female blue crab, spot, striped mullet, and white shrimp each had increases of over 200%. Mature female blue crab was the only category of economically important species that decreased in abundance in the slotted-weir pond catch relative to the standard-weir pond. There was an overall increase in biomass emigration (62%) from the slotted-weir pond (Table 1). The percent changes in biomass between the two ponds was much less, than it was by numbers, for most of the 23 economically important species. Striped mullet, white shrimp, and small blue crabs had the greatest percent increase in biomass in the slotted-weir pond. For trapping data, almost all estuarine-dependent organisms were larger in the standard-weir pond (Table 2, Appendix Figs 1 - 29), with the exception of white shrimp and striped mullet. However, not enough of the annual nursery cycle was studied to make any firm conclusions for white-shrimp. Emigrating striped mullet were nearly 5 times larger in the slotted-weir pond trap catch than in the standard-weir pond trap catch. The species trapped and the order of their abundances were similar in the two experimental ponds (Table 1). The order of abundance of the top eight categories were the same, with minor exceptions. Some 57 species emigrated from the slotted-weir pond whereas 42 emigrated from the standard-weir pond. A single fiddler crab was the only species taken in the catch from the standard-weir pond that did not occur in the slotted-weir pond. Although not always consistent, the slotted-weir trap generally caught more species on a daily basis (Fig. 7). The slotted-weir pond catch had many more organisms early in the study, but catches were about the same in the later half (Fig. 7). Except on a few occasions, the catch biomass was greater in the slotted-weir pond on a daily basis (Fig. 7). Appendix Table 3 lists the catch and biomass for individual trawling stations. Trawling data did not show the differences between the experimental ponds as well as the trapping data. The number of species, total catch, and biomass were not distinctly different between ponds over time (Fig. 8). However, total catches over the study period from all three ponds did indicate that the slotted-weir and control pond had 67% to 103% greater standing crop in terms of numbers, and a 19% to 48% greater standing crop in terms of biomass than the standard-weir pond, respectively (Table 3). These data again demonstrate that standing crop is not an indicator of productivity (as measured by the export from the ponds back towards the Gulf). Standing crop over time was not very different in the two experimental ponds (Fig. 8), nor was overall trawl catch by biomass (Table 3), but export was much greater from the slotted-weir cn 25' w 0- (n 20 'k LIJ 15 J" If, M I M z 101 1 1 1 SFEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31 MAY 15JUN 30JUN 1 5JUL 30JUL 70,000 60,000 X 50,000 M 40,000 30,000 z 20,000 11 ih I1@ %Ii 10,000 0 15FEB 02MAR 17MAR 01APR 16APR CIMAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 80,000- 70,000- 60,000- 50,000- V) V) 40,000- 30,000- Fn 20,000- 10,000- 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN I 5JUL 30JUL POND -------- SLOTTED WEIR - STANDARD WEIR Figure 7. Number of species, total number of individuals, and biomass of all emigrating species taken by the trap in each experimental pond. 25 25' Cl- M 20- LL. 0 Li 15, z 101 15FEB 02MAP 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 24,000 20,000- LLJ 16,000- 12,000, z 8,000 4,000- 0 15 FE8 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 10,000 8,000' Ln 6,000- V) 4,000- \V// 2,000 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND ---- CONTROL ----- SLOTTED WEIR STANDARD WEIR Figure 8. Number of species, total number of individuals, and biomass of all species taken by both trawls combined in each experimental pond. 26 pond by both numbers and biomass as compared to that from the standard-weir pond (Table 1). Total trawl catch of most of the economically important species such as gulf menhaden'. Atlantic croaker, white shrimp, and brown shrimp was greater in the control and slotted-weir ponds than in the standard-weir pond (Table 3). Twenty-seven species were taken by the trawls in the standard-weir pond trawl catch, 29 in the slotted-weir, and 46 in the control pond (Table 3). Trawling indicated little difference in number of species between the two experimental ponds, whereas the trapping data indicated 57 species occurred in the slotted-weir pond and 42 in the standard-weir pond. We have no trap data for the control pond, but based on the trawl data, trap catches there would probably have taken more species than taken emigrating from the ponds having either type of weir. Trends in mean weight are presented in Appendix Figs. 1 - 29 and mean weight of organisms captured by the trawls over the entire study are presented in Table 4. Species Composition Conclusions 1. More organisms (60%) and more biomass (62%) emigrated from the slotted-weir pond than the standard-weir pond during the study period. 2. More species emigrated from the slotted-weir pond (57) than from the standard-weir pond (42) during the study period. 3. The order of species abundance was similar between the two ponds for the study period. 4. Except for striped mullet, which were approximately five times larger in the slotted-weir pond, most economically-important species had a lower mean weight when emigrating from the slotted-weir pond than from the standard-weir pond for the study period. 5. Total trawl catch was higher in the control and slotted-weir ponds than in the standard-weir pond for the study period. 6. More species were taken by the trawls in the control pond (46) as compared to the slotted-weir (29) and standard-weir (27) ponds for the study period. 27 Table 4. Mean weight (grams) of organisms derived from the combined catch from both trawls for the duration of the study. Values are computed for those species which had a total catch of 10 or greater. Species that were not taken in more than one pond are not included. SPECIES STANDARD SLOTTED CONTROL WEIR WEIR male blue crab 34.9 17.9 34.7 immature female crab 14.4 10.0 19.1 pinfish 9.4 7.9 8.4 striped mullet 1.5 6.6 10.8 gulf killifish 3.1 3.2 4.2 brown shrimp 6.4 3.2 1.0 Atlantic croaker 5.7 3.1 2.8 spot 4.4 2.7 1.6 white shrimp 2.7 1.6 0.6 sailfin molly 0.6 1.1 0.7 sheepshead minnow 0.8 1.0 1.4 clown goby 1.1 1.0 bay anchovy 0.9 0.9 0.3 gulf menhaden 0.6 0.6 0.5 inland silverside 0.8 0.6 0.6 rainwater killifish 0.5 0.5 0.5 diamond killifish 0.4 0.5 blue crab (less than 25 mm) 0.4 0.5 0.3 naked goby 0.6 0.4 0.5 darter goby 0.8 0.3 grass shrimp 0.1 0.2 0.2 white mullet 3.8 9.5 28 Environmental Salinity Salinity readings were taken in the experimental ponds at three locations; the environmental stations (just pondward of the chutes), the levee station, and the trawling stations (Figs. 2 and 3). The salinities taken at the environmental stations did not represent the salinity of the entire ponds, especially when the current was incoming. The salinities taken during trawling were more representative of the entire pond because they were taken at different locations within each pond. The levee station was approximately at the midpoint of the middle levee, and readings there nearly equaled the readings of the trawl stations on the days when trawl samples were taken (Fig. 9) and were thus used to represent the experimental pond salinities. Hourly salinity values taken by the Hydrolab instruments (located at the environmental stations) from 17 January 1986 through 30 July 1986 are presented in Appendix Figure 30. No statistical difference was detected between the two Grand Bayou salinity stations (P = 0.76, PROC GLM, SAS Institute 1985), thus the averages of these two readings were used to represent the Grand Bayou salinity. Hereafter, any reference to the Grand Bayou salinity will be to the daily average of sa linity at stations A and B. The salinity in the slotted-weir pond was approximately 1-3 ppt higher than in-the standard-weir pond for the first two months of the study (Fig. 10). (The structures were in place approximately two months prior to the beginning of the study, thus the observed differences early in the study were probably due to the structures.) The bottom of the slotted-weir pond had an approximate 0.3-foot higher elevation than the standard-weir pond. Thus, the slotted-weir pond .volume was 23 percent less than the standard-weir pond volume when the water levels were at the weir crest level in the ponds. The resultant lower volume in the slotted-weir pond may account for the increase in salinity (1-3 ppt) in that pond early in'the study. In addition, if the volumes were the same, the expected differences in salinity and water level would be considerably less than seen in this study. The higher the water levels in the ponds and Grand Bayou increased 251 29 20 CL 15 z 'D 10 V) 5 ENVIRONMENTAL STANDARD WEIR LEVEE ------- TRAWL 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 251 20 a- a_ 10 V) 5-1 ENVIRONMENTAL SLOTTED WEIR LEVEE ------- TRAWL 01 ... I- 15FEB 02MAR 17MAR 0.1APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 1 5JUL 30JUL DATE Figure 9. Daily salinity readings taken at the enviroranental and levee stations, and the mean salinity taken at the trawling stations, for both experimental ponds. mom noun 4010011w@ on w'.00 sweava mom 25' STANDARD WEIR SLOTTED WEIR -------- GRAND BAYOU 20" q- 15- 10, (A 5" 01 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 1 5JUL 30JUL DATE Figure 10. Salinity in both ponds (as measured at the levee stations) and in Grand Bayou (average of stations A and B). 31 above the weir crest level the more similar both ponds became in terms of salinity and water level (Figs. 10 and 11). To compare salinities for the different locations, the data were separated by concurrent time periods (Table 5). (In Grand Bayou, salinity readings began on 4 April 1986 and water level readings began on 4 March 1986.) Over the entire study period, the slotted-weir pond salinity had a lower standard deviation than the standard-weir pond. The standard-weir pond had lower salinities (which deviated greatly from its mean) in the early part of the study, which accounted for this greater overall deviation. When examining data from 4 April through 30 July 1986, Grand Bayou, the slotted-weir pond and the standard-weir pond had decreasing standard deviations, respectively (Table 5). Salinity taken with trawling indicated that the control pond had the highest standard deviation in salinity and the slotted-weir pond had the lowest. Salinities over the entire year, if not more than one year, would be needed to make any firm conclusions on how these structures affect the salinity regime. Water Level The ability to control water levels is of major concern to most marsh managers. Two strong cold front's lowered the water level in Grand Bayou to -14 inches (0'inches = marsh level) early in the study (Fig. 11, Table 5). The water levels in the slotted-weir pond dropped to a minimum of -8 and -9 inches on these two occasions, whereas the water levels dropped to -5 and -5.5 inches in the standard-weir pond (Fig. 11). If the weir crests in both ponds were to the scale that is normally used (1 foot of weir crest per 70 acres of marsh), then water levels would not have dropped as low in either pond. When the water levels dropped in Grand Bayou, the lowest water levels were reached in the slotted-weir pond before the standard-weir.pond. As the water levels rose, the water level in the slotted-weir pond began to rise while the levels were still dropping in the standard-weir pond. Thus for these frontal periods, the slotted-weir would have greater periods of incoming current (traded off with a shorter period of water level decrease), which would allow a greater period of time for larval and/or juvenile organisms to enter the pond. When Grand Bayou water levels were above -6 inches, the pond levels were usually similar. During 10 STANDARD WEIR SLOTTED WEIR -------- GRAND BAYOU 5' Li 2: MARSH LEVEL %-oo z V LAJ > Ld ir I,- 1,V I y -10 11 1 1 WEIR CREST -15 @c vi@ 15FEB 02MAR 17MAR 01APR 16APR 0 1 MAY 16MAY 31 MAY I SJUN 30JUN 15JUL 30JUL . DATE Figure 11. Water level for the experimental ponds and Grand Bayou. 33 Table 5. Summary statistics for the daily physical measurements for the experimental ponds (at the levee station) and Grand Bayou, and physical data collected while trawling in the three ponds. Data are separated by time frames such that valid comparisons can be made. Water levels are presented in inches, with 0 inches being equal to marsh level. N STANDARD STD ERROR MINIMUM MAXIMUM POND (SAMPLES) MEAN DEVIATION OF MEAN VALUE VALUE 15 FEBRUARY - 30 JULY 1987 -------------------------------- SALINITY (ppt) ------------------------------- SLOTTED 165 16.6 2.2 0.2 9.1 20.7 STANDARD 165 14.9 3.0 0.2 7.8 20.4 ------------------------------ WATER TEMPERATURE (C) ---------------------------- SLOTTED 165 23.6 5.2 0.4 8.1 34.7 STANDARD 164 23.5 5.3 0.4 7.1 33.7 -------------------------------- WATER LEVEL (in) ------------------------------ SLOTTED 165 -1.7 3.6 0.3 -9.0 6.0 STANDARD 165 -1.1 2.9 0.2 -5.8 6.0 4 MARCH - 30 JULY 1987 -------------------------------- WATER LEVEL (in) ------------------------------- GRAND BAYOU 148 -2.5 4.2 0.3 -14.3 6.8 SLOTTED 148 -1.4 3.6 0.3 -9.0 6.0 STANDARD 148 -0.8 3.0 0.2 -5.8 6.0 4 APRIL - 30 JULY 1987 -------------------------------- SALINITY (ppt) ------------------------------- GRAND BAYOU 117 17.1 2.4 0.2 11.7 21.0 SLOTTED 117 17.4 1.8 0.2 14.4 20.7 STANDARD 117 16.6 1.4 0.1 13.7 20.4 ------------------------------ WATER TEMPERATURE (C) ---------------------------- GRAND BAYOU 117 26.4 3.6 0.3 17.7 32.3 SLOTTED 117 26.0 3.5 0.3 16.0 34.7 STANDARD 117 26.0 3.5 0.3 16.2 33.7 TRAWLING DATA -------------------------------- SALINITY (ppt) ------------------------------- CONTROL 48 16.2 2.9 0.4 9.1 20.6 SLOTTED 48 16.8 2.3 0.3 12.2 20.3 STANDARD 48 15.3 2.8 0.4 9.1 20.0 ----------------------------- WATER TEMPERATURE (C) ----------------------------- CONTROL 48 28.3 5.3 0.8 18.0 38.3 SLOTTED 48 27.0 4.6 0.7 17.8 35.8 STANDARD 48 26.8 4.7 0.7 18.2 35.6 34 extremely low water levels in March, the slotted weir buffered water level changes in range and time as compared to Grand Bayou (Figure 11), but not as much as the standard weir. The short-term drops in water levels from April through July were buffered about the same by both structures. The water levels were slightly more variable over the entire study in the slotted-weir pond than in the standard -weir pond (Table 5). Apparently, as overall water level increased above crest levels, both structures exhibited about the same water level characteristics and only when water levels declined to near crest level did the two structures differ in their water level characteristics. Appendix Figure 31 contains hourly water level values taken by the Leupold-Stevens gauges from 17 January 1986 through 30 July 1986. Water Temperature No"statistical difference was detected between Stations A and B in Grand Bayou (P = 0.92, PROC GLM, SAS Institute 1985). No obvious differences in water temperature were noticed between the two experimen@al ponds (Table 5, Appendix Fig. 32) at the levee stations. Environmental Conclusions 1. Both structures reduced the salinity changes, when compared to Grand Bayou, with the slotted-weir pond having the lower standard deviation than the standard-weir pond for the overall study period (even though the slotted-weir pond had 23% less volume). Data should be collected from all times of one or more years to make firm conclusions on the effect these two structures have on the salinity regime. 2. As Grand Bayou water levels increased above the weir crest level, the experimental ponds became more similar in water level and salinity for this study period at least. 3. Water levels in the slotted-weir pond were 3 to 4 inches lo,wer than the standard-weir pond when water levels were extremely low in Grand Bayou (-14 inches), but similar between the experimental ponds when water levels were above the weir crest. 35 4. No obvious differences in water temperatures were detected between the two experimental ponds and Grand Bayou for the study period. 36 GENERAL DISCUSSION Each marsh management situation may differ in terms of the marsh type, location relative to the Gulf, desired resource use, and funds avaifable for management. Any type of marsh management will require a trade off of time, money, and certain natural resources. Historically, weirs have been installed primarily to maintain minimum water levels for human access and improve habitat for waterfowl and furbearers. Recently these weirs have been recommended to reduce saltwater intrusion and erosion (DaV4s and Gagliano 1983). There is no direct evidence that weirs reduce erosion, and only in certain hydrological situations do they reduce saltwater intrusion. Herke et al. (1987b) demonstrated the fisheries losses due to weir construction. Chabreck and Hoffpauir (1965), Chabreck (1968), and Wicker et al. (1983) discussed the benefits of weirs to furbearers and waterfowl. Reduced growth of saltmarsh cordgrass in water-logged soils (a condition often found in semi-impounded areas) has been demonstrated by Mendelssohn and Seneca (1980) and Mendelssohn et al. (1980). The resource manager must consider these and possibly other asp ects when making marsh management decisions. Thus, the purpose of this study was to test the effects of a management alternative that would improve estuarine-dependent fisheries production, thereby providing an additional aspect for managerial consideration. The slotted weir allowed the emigration of 241% more brown shrimp and 82% more brown shrimp biomass than the standard weir. Although the complete annual cycle of most other species was not covered by the study, the total catch of all emigrating species was 60% higher (62% by biomass) in the slotted-weir pond. Although the total biomass of emigrants was less, the average size of an economically-important organism (with the major exception of striped mullet) was larger in the standard-weir pond. . Comparison of the results of this study to that of Herke et al. (1987b) allows a look at four structural alternatives, all'monitored at the same study site: standard weir, slotted weir, standard weir set at 12 inches below marsh level, and no structure. The most obvious drawback to the comparison is that the Herke et al. (1987b) data were 37 from years other than the present study. Table 6 presents comparative da'ta (15 February through 30 July) on these four structures. It is obvious that the most fisheries export would generally occur with no structure. Comparison of brown shrimp catch by date for the four structures indicates that the absence of a structure allows the greatest emigration, while the standard fixed-crest weir allows the least (Fig. 12). Since any type of structure placed in the path of these migrating organisms apparently impedes movement, the objective of this study was to examine an alternative to the fixed-crest weir in the coastal habitat, which would more adequately balance the resource use for all forms of wildlife. The slotted-weir appears to be a compromise (between no weir and a standard weir) for both fisheries and hydrologic balance. The slotted weir apparently yields median results between the control pond (early and abundant immigration, early emigration, low mean size, and high rate of cycling) and the standard weir (later and less abundant immigration, delayed emigration, increasingly greater mean size, and low rate of cycling). Although the hydrologic data in this study only cover parts of the winter and summer regime, it appears the greater discrepancy in hydrology between the ponds would occur in the winter, especially during cold fronts. (A possible management practice may be to close the slot during strong cold fronts.) The effect of the slotted and standard weir for management of the hydrologic regime should be further studied and should encompass the entire annual cycle. The width of the slot would be subject to management requirements and the hydrodynamics of the area concerned. The widest slot that will still achieve the rest of the management goals would be desired for coastal fisheries benefits. Data from this study can be used as an example, but not necessarily as a model. With these empirical data and knowledge of hydrologic principles, formulas or models could be derived to estimate the slot width for a given area to meet management criteria. The weir crests (see Methods and Procedure) were wider per area of marsh affected than is generally used in practice. Thus, the absolute differences in salinity and water levels between the two experimental ponds in this study probably were greater than would be expected had the marsh area been larger or the weir crests shorter. 38 Table 6. Catch of abundant, or economically-important, organisms taken by Herke et al. (1987b)(15 February 1983 through 30 July 1983) and this study (15 February 1986 through 30 July 1986). Herke et al. (1987b) This Study No Low Standard 1 Slotted Standard Species Structure Weir Weir Weir gulf menhaden 834,045 73,717 2793,171 219,279 grass shrimp 324,767 331,871 388,977 270,907 brown shrimp 285,954 93,486 97,694 28,681 Atlantic croaker 228,296 47,728 34,176 22,193 blue crab (< 25 mm) 226,833 151,567 6,576 472 bay anchovy 169,771 22,820 1P970 1,614 imm. female blue crab 97,968 75,259 28,364 9,018 inland silverside 95,648 80,343 36,766 13,451 male blue crab 75,711 60,431 24,874 8,689 spot 16,496 9yO22 15,805 4,045 striped mullet 10,603 11,484 12y921 3,560 gulf killifish 6,181 5,184 11,988 6,350 naked goby 5,998 3,033 2,071 1,'859 sheepshead minnow 4,795 2,726 7,464 3,540 white mullet 2,141 3,416 21,773 15,902 pinfish 207 155 6,115 529 white shrimp 695 15 2,222 368 red drum 540 80 18 2 sand seatrout 490 135 37 18 southern flounder 30 12 115 13 spotted seatrout 9 0 2 0 1 Standard weir with crest set 12 inches below average marsh soil level. 39 30,000- 20,000 1983 U-1 M ---- NO WEIR :M -LOW WEIR D z 10,000. "It, ;hJ 01- 15APR 30APR 15MAY 30MAY 14JUN 29JUM 14JUL 29JUL 30,000- 1984 20,000- -----NO WEIR ch -LOW WEIR z 10,000 It 01 1 15APR 30APR 15MAY 30MAY 14-JUN 29JUN 14JUL 29JUL 30,000. 1986 CC 20,000- ---- SLOTTED WEIR W M STANDARD WEIR z 10,000. 01 15APR 30APR 15MAY 30MAY 14-JUN 29JUN 14JUL 29JUL DATE SET Figure 12. Brown shrimp catch for 1983 and 1984 (Herke et al. 1987b) and 1986 (this study) at the experimental ponds. The weir crest was set at 12 inches below average marsh soil ground level in 1983 and 1984. 40 Also, the slotted-weir pond had less volume, which should have increased the salinity and water level variability. The length of weir crest, marsh area affected, depth, ratio of marsh to open water, amount of fresh water inflow, and other considerations should be included when calculating the slot width. If a marsh is to be managed by water-control structures, they should be customized to the specific resource needs. A slotted weir may be inappropriate in a fresh or intermediate marsh, because saltwater exclusion may be the primary management goal. Cowan et al. (1986) found that most marsh management practices in the fresh and intermediate marshes were generally successful. However, they concluded marsh management practices in the brackish to saline habitats were, by and large, only marginally successful. Indications are that the brackish and saline marshes may need more water exchange and fluctuations to allow oxidation of the soils and reduce the stress upon the natural plants that dominate that environment. From this study it is evident that, if a weir is considered as a coastal marsh management tool, a slotted weir would be more beneficial to fisheries resources. Additional research should be conducted to determine the compatibility of slotted weirs with management goals which are designed to benefit. other forms of wildlife, and preserve and enhance marsh vegetation. As a minimum, such investigations should: 1. Evaluate the effectiveness of the standard and slotted weir in reducing erosion and stress on the native plants. 2. Evaluate the effectiveness of these structures in providing habitat for other forms of wildlife. 3. Further evaluate the effect of these structures on seasonal salinity patterns and water levels. 4. Evaluate the effect of these structures on other estuarine-dependent fishes and crustaceans (the target species for this study was brown shrimp). These evaluations could be done simultaneously to reduce costs. They should also cover enough years (probably 5 to 7) to provide a complete evaluation of the short- and long-term effects of alteration of the hydrologic regime on the marsh vegetation and all forms of wildlife. 41 General Conclusion 1. The slotted weir allowed greater numbers and biomass of brown shrimp to emigrate back toward the Gulf. Resource managers should consider the slotted weir as an alternative to the standard fixed-crest weir. 42 CONCLUSIONS The conclusions for each section are reproduced here for convenience of the reader. The study only covered a 5.5 month period (15 February through 30 July), thus these conclusions are based on that period alone. Conclusions for species other than brown shrimp (target species for this study) and hydrologic factors would require a study which at least examines an entire yearly cycle. Brown Shrimp Conclusions 1. The slotted weir allowed more individuals (241% more) and biomass (84% more) of brown shrimp to emigrate back towards the Gulf than did the standard weir. 2. Brown shrimp emigrated from the standard-weir pond later, and at a larger size, than from the slotted-weir pond. 3. Recruitment into the nursery and emigration were delayed and reduced by both str*uctures, but more so by the standard weir. 4. Both structures reduced the cycling of brown shrimp in and out of the marsh nursery with the standard weir reducing it more. 5. Use of a slotted weir should result in more brown shrimp production than would use of a standard weir. Composite Species Conclusions 1. More organisms (60%) and more biomass (62%) emigrated from the slotted-weir pond than the standard-weir pond during the study period. 2. More species emigrated from the slotted-weir pond (57) than from the standard-weir pond (42) during the study period. 3. The order of species abundance was similar between the two ponds for the study period. 43 4. Except for striped mullet, which were approximately 5 times larger in the slotted-weir pond, most economically-important species had a lower mean weight when emigrating from the slotted-weir pond than from the standard-weir pond for the study period. 5. Total trawl catch was higher in the control and slotted-weir ponds than in the standard-weir pond for the study period. 6. More species were taken by the trawls in the control pond (46) as compared to the slotted-weir (29) and standard-weir (27) ponds for the study period. Environmental Conclusions 1. Both structures reduced the salinity changes, when compared to Grand Bayou, with the slotted-weir pond having the lower standard deviation than the standard-weir pond for the overall study period (even though the slotted-weir pond had 23% less volume). Data should be collected from all times of one or more years to make firm conclusions on the effect these two structures have on the salinity regime. 2. As Grand Bayou water levels increased above the weir crest level, the more the experimental ponds became similar in water level and salinity for the study period. 3. Water levels in the slotted-weir pond were 3 to 4 inches lower than the standard-weir pond when water levels were extremely low in Grand Bayou (-14 inches), but similar between the experimental ponds when water levels were above the weir crest. General Conclusion 1. The slotted weir allowed greater numbers and biomass of brown shrimp to emigrate back toward the Gulf. Resource managers should consider the slotted weir as an alternative to the standard fixed-crest weir. 44 LITERATURE CITED Bradshaw W. H. 1985. Relative abundances of small brown shrimp as influenced by semi-impoundment. M.S. Thesis, Louisiana State University, Baton Rouge. 61 p. Chabreck, R. H. 1968. Weirs, plugs, and artificial potholes for the management of wildlife in coastal marshes. Pages 178-192 in J. D. Newsom editor. Proceedings of the Marsh and Estuary Management Symposium. Division of Continuing Education,, Louisiana State University, Baton Rouge. Chabreck, R. H. and C. M. Hoffpau ir. 1965. The use of weirs in coastal marsh management in Louisiana. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners. 16:103-112. Cowan J. H., R. E. Turner, and Donald R. Cahoon. 1986. A preliminary analysis of marsh management plans in coastal Louisiana. Coastal Ecology Institute, Center for Wetland Resources, Louisiana State University, Baton Rouge, Louisiana. Work Assignment 9. Davis, D. J. and S. M. Gagliano. 1983. LaFourche Realty wetlands marsh management program. Coastal Environments, Inc., 1260 Main St., Baton Rouge, Louisiana. 43 p. Herke, W. H. 1968. Weirs, potholes and fishery management. Pages 193-211 in J. D. Newsom, editor. Proceedings of the Marsh and Estuary Management Symposium. Division of Continuing Education, Louisiana State University, Baton Rouge. Herke, W. H. 1971. Use of natural, and semi-impounded, Louisiana tidal marshes as nurseries for fishes and crustaceans. Ph.D. Dissertation, Louisiana State University, Baton Rouge. 264 D. Univ. Microfilms, Ann Arbor, Mich. (Diss. Abs. 32:2654-B). Herke, W. H* 1978* A subsampler for estimating the number and length frequency of small, preserved nektonic organisms. Fisheries Bulletin 76(2):490-494. Herke, W. H. 1979. Some effects of semi-impoundment on coastal Louisiana fish and crustacean nursery usage. Pages 325-346 'in J. W. Day, Jr., D. D. Culley, Jr., R. E. Turner, and A. J. Mumphrey, Jr. editors. Proceedings of the Third Coastal Marsh and Estuary Management Symposium, Division of Continuing Education, Louisiana State University, Baton Rouge. Herke, W. H., B. D. Rogers, and E. E. Knudsen. 1984a. Habits and habitats of young spotted seatrout in Louisiana marshes. Research Report No. 3. School of Forestry, Wildlife, and Fisheries, Louisiana State University, Baton Rouge. 48 p. 45 Herke, W. H., B. D. Rogers, and J. A. Grimes. 1984b. A study of the seasonal presence, relative abundance, movements, and use of habitat types by estuarine-dependent fishes and economically-important decapod crustaceans on the Sabine National Wildlife Refuge. Final Report. Louisiana Cooperative Fish and Wildlife Research Unit, Louisiana State University, Baton Rouge. 3 volumes. 933 p. Herke, W. H., E. E. Knudsen,, B. D. Rogers, and V. L. Prenger. 1985. Effects of a fixed-crest water-control structure on the abundance of the fish and crustaceans migrating from a shallow marsh nursery toward the Gulf of Mexico. Estuaries 8(2A):21A. Herke, W. H., M. W. Wengert, and M. E. Lagory. 1987a. Abundance of brown shrimp in a natural and semi-impounded marsh nursery areas: relation to temperature and salinity. Northeast Gulf Science 9(l): In press. Herke, W. H., E. E. Knudsen, Z. X. Chen, N. S. Green, P. A. Knudsen, and B. D. Rogers. 1987b. Final report for the Cameron-Creole Watershed Fisheries Investigations. Louisiana Cooperative Fish and Wildlife Research Unit, School of Forestry, Wildlife, and Fisheries, Louisiana State University Agricultural Center, Baton Rouge. In press. King, B. D., 111. 1971. Study of migratory patterns of fish and shellfish through a natural pass. Texas Parks and Wildilfe Department. Technical Series No. 9. Austin, Texas. 54 p. Mendelssohn, I. A. and E. D. Seneca. 1980. The influence of soil drainage on the growth of salt marsh cordgrass Spartina alterniflora in North Carolina. Estuarine and Coastal Marine Science (1980)11:27-40. Mendelssohn, I. A., K. L. McKee, and W. H. Patrick, Jr. 1980. Oxygen deficiency in Spartina alterniflora roots: metabolic adaptation to anoxia. Science 214:439-441. Perry, W. G. 1981. Seasonal abundance and distribution of brown and white shrimp in a semi-impounded Louisiana coastal marsh. Proceedings of the Louisiana Academy of Science 44:102-111. Rogers, B. D. 1985. A small push-otter trawl for use in shallow marshes. North American Journal of Fishery Management 5(3A):411-413. Rogers, B. D. and W. H. Herke. 1985a. Temporal patterns and size characteristics of migrating juvenile fishes and crustaceans in a Louisiana marsh. Research Report No. 5. School of Forestry, Wildlife and Fisheries, Louisiana State University, Baton Rouge. 81 P. 46 Rogers, B. D. and W. H. Herke. 1985b. Estuarine-dependent fish and crustacean movements and weir management. Pages 210-219 in C. F. Bryan, P. J. Zwank, and R. H. Chabreck, editors. Proceedings of the Fourth Coastal Marsh and Estuary Management Symposium. Louisiana Cooperative Fish and Wildife Research Unit, Louisiana State University, Baton Rouge. SAS Institute Inc. 1985. SAS User's Guide: Statistics. 1985 edition. SAS Institute Inc. Cary, NC. 956p. Schultz, T. S. 1985. Diel movement of brown shrimp (Penaeus aztecus) at a southwest Louisiana estuarine lake-marsh interface. M. S. Thesis, Louisiana State University, Baton Rouge. 93 p. Wicker, K. M., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve: Evaluation of wetland management techniques. Louisiana Department of Natural Resources, Coastal Management Section, Baton Rouge. 86 p, 8 plates. Wengert, M. W., Jr. 1972. Dynamics of the brown shrimp, Penaeus aztecus aztecus Ives 1891, in the estuarine area of Marsh Island, Louisiana in 1971. M.S. Thesis, Louisiana State University, Baton Rouge. 94 p. 47 Appendix Table 1. Analysis of variance (PROC GLM, SAS 1985) for brown shrimp (log number + 1) for trawling data. Date is further analyzed by its' linear (D), quadratic (D*D), and cubic (DytD*D) components. GENERAL LINEAR MODELS PROCEDURE DEPENDENT VARIABLE: log catch + I SOURCE DF SUM OF SQUARES F VALUE PR > F R-SQUARE (TYPE I) MODEL ill 300.29 9.17 0.0001 0.98 POND 2 41.34 70.05 0.0001 LOCATION 1 0.02 0.05 0.8229 D 1 0.02 0.07 0.8004 D*D 1 91.25 309.26 0.0001 D*D*D 1 1.74 5.89 0.0248 DATE 7 6.69 3.24 0.0183 POND*LOCATION 2 0.03 0.05 0.9488 D*POND 2 67.47 114.34 0.0001 D*D*POND 2 4.33 7.34 0.0041 D*D*D*POND 2 0.44 0.74 0.4907 PONDYcDATE 14 12.78 3.09 0.0106 LOCATIONY-DATE 10 1.86 0.63 0.7718 POND*LOCATION*DATE 20 5.62 0.95 0.5423 GEAR 1 12.39 41.98 0.0001 POND*GEAR 2 0.59 1.00 0.3870 LOCATION*GEAR 1 0.13 0.46 0.5077 GEAR*DATE 10 29.76 10.09 0.0001 *YC POND*GEAR*DATE 20 21.71 3.68 0.0027 POND*LOCATION*GEAR 2 0.69 1.13 0.3417 LOCATION*GEAR*DATE 10 1.46 0.50 0.8731 ERROR 20 5.90 CORRECTED TOTAL 131 306.19 48 Appendix Table 2. List of all species, catch and biomass for the entire study taken by the traps and trawls combined. SCIENTIFIC COMMON NUMBER BIOMASS NAME NAME (G) Palaemonetes sp. grass shrimp 761,612 291,776 Brevoortia patronus gulf menhaden 566,330 539,085 Penaeus aztecus brown shrimp 132,466 706,896 Menidia beryllina inland silverside 66,968 56,890 Micropogonias undulatus Atlantic croaker 59,771 419,705 C. sapidus, immature female im-tu e female blue crab 37,750 827,757 Mugil curen- white mullet 37,725 276,877 Callinectes sapidus, male male blue crab 33,926 1,834,874 Leiostomus xanthurus spot 31,471 106,798 Fundulus grandis gulf killifish 18,417 80,655 Mugil cephalus striped mullet 17,542 709,449 Cyprinodon variegatus sheepshead minnow 11,103 15,520 Anchoa mitchilli bay anchovy 10,883 7,833 Adinia xenica diamond killifish 8,291 3,664 Lagodon rhomboides pinfish 81035 84,240 Callinectes sapidus blue crab (less than 25 mm) 7,123 2,896 Penaeus setiferus white shrimp 6,967 14,220 Poecilia latipinna sailfin molly 4,765 5,687 Gobiosoma bosci naked goby 4,308 2,757 Gobionellus boleosoma darter goby 3,382 2,998 Lucania parva rainwater killifish 2,704 1,546 C. sapidus, mature female mature female blue 770 134,902 Citharichthys spilopterus bay whiff 610 5,815 Gobionellus hastatus sharptail goby 421 6,182 Symphurus plagiusa blackcheek tonguefish 416 4,121 Fundulus pulvereus bayou killifish 191 235 Myrophis punctatus speckled worm eel 187 2,088 Paralichthys lethostigma southern flounder 154 21,024 Microgobius gulosus clown goby 145 143 Gambusia affinis mosquitofish 124 62 Elops saurus ladyfish ill 782 Rithropanopeus harisii mud crab 96 25 Elops saurus leptocephalus ladyfish leptocephalus 74 7 Cynoscion arenarius; sand seatrout 72 1,344 Sphoeroides parvus least puffer 58 103 Syngnathus sp. pipefish 47 54 Membras martinica rough silverside 34 73 Sciaenops ocellatus red drum 22 4,258 Lepomis microlophus redear sunfish 22 188 Pogonias cromis black drum 12 581 Caranx hippos crevalle jack 12 46 Microgobius thalassinus green goby 12 5 Arius felis hardhead catfish 9 1,421 Dorosoma petenense threadfin shad 7 25 Archosargus probatocephalus sheepshead 7 71 49 Appendix Table 2. continued. SCIENTIFIC COMMON NUMBER BIOMASS NAME ' NAME (G) Cynoscion nebulosus spotted seatrout 6 88 Dorosoma cepedianum gizzard shad 6 64 Bairdiella chrysoura silver perch 5 34 Oligoplites saurus leatherjacket 5 4 Fundulus similis longnose killifish 5 52 Synodus foetens inshore lizard fish 4 241 Pomatomus saltatrix bluefish 3 2 Gobioides broussoneti violet goby 3 331 Trichiurus lepturus Atlantic cutlassfish 3 290 Malaclemys terrapin diamondback terrapin 2 516 Syngnathus louisianae chain pipefish 2 9 M. punctatus leptocephalus worm eel leptocephalus 2 40 Porichthys plectrodon Atlantic midshipman 1 3 Orthopristis chrysoptera pigfish 1 1 Alpheus sp. snapping shrimp 1 2 Uca sp. fiddler crab 1 2 Harengula jaguana scaled sardine 1 1 Chaetodipterus faber Atlantic spadefish 1 17 Lepomis macrochirus bluegill 1 5 Dormitator maculatus fat sleeper 1 5 TOTAL 1,835,209 6,177,464 50 Appendix Table 3. List of species, total catch, and total biomass for trawling data by station and gear for the entire study. Station WB (standard-weir, back - six-foot trawl) Station WB (standard-weir, back - sixteen-foot trawl) SPECIES NUMBER BIOMASS (g) SPECIES NUMBER BIOMASS (g) grass shrimp 18,854 2,121 gulf menhaden 1,114 1,011 gulf menhaden 2,300 733 Atlantic croaker 482 2,474 inland silverside 2,136 1,578 brown shrimp 388 3,008 striped mullet 499 380 spot 340 1,736 spot 256 390 inland silverside 324 294 bay anchovy 229 166 grass shrimp 261 63 naked goby 129 68 white shrimp 197 851 rainwater killifish 122 60 bay anchovy 192 168 white shrimp 114 101 pinfish 181 1,864 brown shrimp 87 244 male blue crab 76 2,920 pinfish 73 26 inunature female crab 72 1,014 sailfin molly 45 27 white mullet 4 37 immature female crab 26 302 striped mullet 3 301 diamond killifish 24 10 blue crab (less than 25mm) 3 1 sheepshead minnow 23 22 naked goby 3 4 male blue crab 22 230 darter goby 2 2 blue crab (less than 25 mm) 14 5 clown goby 2 3 gulf killifish 13 46 ladyfish 2 16 white mullet 12 14 pipefish 1 1 pipef ish 12 14 TOTAL 3,647 15,771 Atlantic croaker 7 33 clown goby 7 8 mosquitofish 5 3 ladyfish 5 1 darter goby 3 3 ladyfish leptocephalus 3 0 diamondback terrapin 1 45 redear sunfish 1 6 sharptail goby 1 1 TOTAL 25,023 6,634 Station WM (standard-weir, mouth six-foot trawl) Station WM (standard-weir. mouth - sixteen-foot trawl) SPECIES NUMBER BIOMASS SPECIES NUMBER BIOMASS (g) grass shrimp 10,203 1,833 gulf menhaden 2,512 1,640 inland silverside 2,589 1,842 inland silverside 704 640 gulf menhaden 518 176 Atlantic croaker 422 2,714 bay anchovy 213 204 spot 363 2,231 brown shrimp 127 230 brown shrimp 277 2,133 naked goby 50 34 grass shrimp 265 65 white shrimp 49 17 bay anchovy 203 212 Spot 46 108 pinfish 186 2,592 striped mullet 44 55 white shrimp 80 223 rainwater killifish 37 20 male blue crab 38 1,862 pinfish 37 16 immature female crab 25 511 sailfin molly 32 18 clown goby 7 7 diamond killifish 22 8 white mullet 6 32 immature female crab 13 132 striped mullet 2 77 male blue crab 10 78 spatted seatrout 1 43 darter goby 10 5 rainwater killifish 1 1 Atlantic croaker 8 7 redear sunfish 1 14 sheepshead minnow 8 4 darter goby 1 2 gulf killifish 7 17 naked goby 1 0 blue crab (less than 25mm) 6 3 ladyfish 1 10 clown goby 4 3 5,096 15.010 pipefish 3 2 mosquitofish 1 0 ladyfish leptocephalus 1 0 ladyfish 1 2 TOTAL 14,039 4,817 51 Appendix Table 3. continued. Sta,tion EB (slotted-weir, back - six-foot trawl) Station EB (slotted-weir. back - sixteen-foot trawl) SPECIES NUMBER BIOMASS (g) SPECIES NUMBER BIOMASS (g) grass shrimp 21,100 3,202 gulf.menhaden 3.729 3,020 inland silverside 1,671 939 spot 1,036 2,910 gulf menhaden 1,226 488 Atlantic croaker 653 2,176 white shrimp 430 198 brown shrimp 369 1,374 spot 291 319 white shrimp 336 990 rainwater killifish 250 107 grass shrimp 321 66 brown shrimp 206 483 inland silverside 264 220 Atlantic croaker 99 166 pinfish 246 1,989 bay anchovy 74 53 bay anchovy 188 161 naked goby 70 19 male blue crab 87 1.705 pinfish 36 61 immature female crab 85 651 male blue crab 31 311 striped mullet 19 1,080 immature female crab 25 252 clown goby 4 4 striped mullet 19 137 blue crab (less than 25 mm) 3 2 darter gaby 14 4 southern flounder 3 285 sheepshead minnow 12 10 blackcheek tonguefish 3 33 gulf killifish 11 31 least puffer 2 8 clown goby 11 9 naked goby 2 1 blue crab (less than 25mm) 10 5 spatted seatrout 1 21 ladyfish 6 1 rainwater killifish 1 1 diamond killifish 2 1 white mullet 1 14 white mullet 2 31 ladyfish 1 3 sailfin molly 2 3 TOTAL 7,354 16,717 TOTAL 25,598 6,833 Station EM (slotted-weir, mouth six-foot trawl) Station EM (slotted-weir, mouth - sixteen-foot trawl) SPECIES NUMBER BIOMASS (g) SPECIES NUMBER BIOMASS (g) grass shrimp 31.895 5,393 gulf menhaden 2,922 1,969 inland silverside 4,017 2,429 spot 1.185 3,640 gulf menhaden 2,512 951 grass shrimp 582 127 white shrimp 283 173 inland silverside 537 501 striped mullet 264 99 Atlantic croaker 508 1,565 rainwater killifish 259 121 brown shrimp 408 1,387 bay anchovy 187 157 pinfish 372 3,223 brown shrimp 179 443 white shrimp 292 792 spot 78 131 bay anchovy 192 183 naked goby 78 28 immature female crab 45 681 immature female crab 42 378 male blue crab 43 1,049 gulf killifish 34 113 rainwater killifish 11 5 Atlant ic croaker 33 70 striped mullet 10 741 sheepshead minnow 29 29 clown goby 7 9 diamond killifish 25 12 naked goby 7 6 male blue crab 20 169 white mullet 3 23 pinfish 11 3 southern flounder 2 3 sailfin molly 10 10 bay whiff 1 1 darter goby 8 4 sheepshead minnow 1 2 blue crab (less than 25mm) 7 3 pipefish 1 1 ladyfish 6 2 TOTAL 7.129 15,910 mud crab 5 1 mosquitofish 3 1 clown goby 3 2 white mullet 1 12 ladyfish leptocephalus 1 0 southern flounder 1 4 TOTAL 39,991 10,740 -A 52 Appendix Table 3. continued. Station CB (control, back - six-foot trawl) Station CB (control. back - sixteen-foot trawl) SPECIES NUMBER BIOMASS (g) SPECIES NUMBER BIOMASS grass shrimp 9,451 1,664 gulf menhaden 24,811 11,966 gulf menhaden 8,862 2,453 spot 4,264 7,190 white shrimp 1.329 512 brown shrimp 959 1.221 brown shrimp 1,121 502 grass shrimp 481 81 spot 806 639 bay anchovy 374 210 inland silverside 625 311 Atlantic croaker 358 1,333 bay anchovy 464 149 white shrimp 326 292 rainwater killifish 427 203 inland silverside 173 145 Atlantic croaker 40 23 pinfish 126 1,259 striped mullet 29 51 striped mullet 44 1,519 blue crab (less than 25mm) 20 6 male blue crab 16 341 ladyfish leptocaphalus 16 1 mud crab 13 8 pinfish 15 3 immature female crab 13 12 sailfin molly 13 8 sand seatrout 10 64 sheepshead minnow 11 12 white mullet 10 86 mud crab 7 2 southern flounder 10 100 gulf killifish 7 17 crevalle Jack 8 35 mosquitofish 7 1 naked goby 8 7 male blue crab 6 183 rainwater killifish 6 5 white mullet 4 16 threadfin shad 4 17 darter goby 3 2 sheepshead minnow 3 6 naked goby 3 0 redear sunfish 3 22 chain pipefish 2 9 red drum 2 81 pipefish 1 0 silver perch 2 19 immature female crab 1 2 black drum 2 532 clown goby 1 1 sailfin molly 2 2 TOTAL 23,271 6,773 blue crab (less than 25 mm) 2 1 ladyfish 2 92 spotted seatrout I I hardhead catfish 1 21 least puffer 1 3 diamondback terrapin 1 471 diamond killifish I I pipefish 1 1 darter goby 1 1 TOTAL 32,039 27,146 Station CH (control, mouth - six-foot trawl) Station CM (control, mouth - sixteen-foot trawl) SPECIES NUMBER BIOMASS (g) SPECIES NUMBER BIOMASS (g) grass shrimp 8,201 1,958 gulf menhaden 12,558 7,824 gulf menhaden 4,816 1,251 spot 2.176 4,605 inland silverside 3,538 2,238 bay anchovy 1,510 692 bay anchovy 3,473 880 brown shrimp 919 1,430 brown shrimp 1,051 728 Atlantic croaker 507 1,740 spot 780 644 white shrimp 191 316 white shrimp 750 317 inland silverside 173 165 rainwater killifish 300 139 grass shrimp 114 24 Atlantic croaker 285 214 pinfish 63 821 striped mullet 117 92 male blue crab 13 719 ladyfish leptocephalus 52 6 immature female crab 12 638 pinfish 45 2 striped mullet 11 500 naked goby 23 10 southern flounder 8 16 rough silverside 21 48 sand.seatrout 7 36 sheepshead minnow 12 18 white mullet 7 97 blue crab (less than 25mm) 10 3 rough silverside 7 14 immature female crab 9 15 least puffer 4 8 gulf killifish 7 43 naked goby 4 3 pipefish 7 7 crevalle Jack 3 9 redear sunfish 6 52 inshore lizard fish 3 186 southern flounder 2 3 mud crab 3 1 leatherjacket 1 2 rainwater killifish 3 3 pigfish 1 1 leatherjacket 2 2 scaled sardine 1 1 spotted seatrout 1 2 sailfin molly 1 0 hardhead catfish 1 10 male blue crab 1 7 threadfin shad 1 2 TOTAL 23,510 8,679 bay whiff I I gizzard shad 1 18 r:d:ar ;unfish 1 14 d r ar oby 1 0 green goby I I ladyfish leptocephalus 1 0 blackcheek tonguefish 1 11 TOTAL 18.308 19,906 53 70,000' 60,000- 50,000' Uj cn 40,000. 30,000- z 20,000- 10,000 0 1 ,Nas i - I - I 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 60,0001 40,000- V) V) 0 0 20,000' M 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 3041UL 5 03 FJ 2 z iAMi < 01 1 15 FEB 02,VAR 744R 01APR 16APR 01@tAY 6PAY 31 MAY '5@UN LOJUN 1511JL ','Ck-,JL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 1. Number, biomass, and mean weight of gulf menhaden taken by the traps in each experimental pond. 54 12,000 A (Y- 8,000- LLI M z 4,00& 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 7,000- 6,000- 5,000- V) 4,000 V) 3,000- 2 2,000 1,000. 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2.01 1.54 1.0 < 0-5@ 0.011 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 3',MAY 15JUN 30JUN 15JUL 30JUL DATE POND ---- CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 2. Number, biomass, and mean weight of gulf menhaden taken by trawls in each pond. 55 3,000' 2,000 M z 1,000. it it ol 01 15FEB 02MAR 17MAR 01APR 1 6APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 30,000- 20,000- (A V) 0 10,000- M 01- 15FEB 02MAR 17MAR 01 APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 40 30 r W 20' 3: z < 10 LU 01F 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 1 5JUL 30JUL DATE SET POND ----- SLOTTED WEIR STANDARD WEIR It Appendix Figure 3. Number, biomass, and mean weight of Atlantic croaker taken by the traps in each experimental pond. 56 500* 400, LAJ co 300, Z) 200* z 100, 0 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 1,6001 1,200- (A (A 800, 400' 0' 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JLII In-1111 32' 24' 16- z < 8. 0 T- I 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND ---- CONTROL ------- SLOTTED WEIR STANDARD WEIR Appendix Figure 4. Number, biomass, and mean weight of Atlantic croaker taken by trawls in each pond. 57 1,200- 800" M Z) 400 fill it It 0 i 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 1 SJUN 30JUN 15JUL 30JUL 4,000- 3,000- V) 2,000- it M 1,000- f I it 01- 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 181 12, 6, 0 '5@'EB 02MAR 17 MAP 0'AP3 16APR 01MAY 16MAY 31MAY lf,JUN 3()JtN '5kL ')!LL DATE SE"Ir' POND ----- SLOTTED WEIR STANDARD WEIR 141, JIV-41 1 f Appendix Figure 5. Number, biomass, and mean weight of spot taken by the traps in each experimental pond. 58 1,600' Cy- 1,200- Lj Co 800, z 4001 ------------- 0- 1@r I 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2,0001 U ol 1,500 V) V) 1,000 Co 500' 01 1 1 i I I I 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 15, 10, --------------------- --- 01 I 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15jUL 30JUL 15FEB 02MAR 17MAR 01APR DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 6. Number, biomass, and mean weight of spot taken by trawls in each pond. 39 30' 20, M z 10. --------------------- Oi , , I , - I ' ' I ' ' I 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 4,000- 3,000- V) V) 2,000- 0 1,000- 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 1500, 1000, z 500 Lj Oi 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR STANDARD WEIR Appendix Figure 7. Number, biomass, and mean weight of southern flounder taken by the traps in each experimental pond. 60 10, 8' 6' M 4* z 2' 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL -300 200 V) V) 0 100, 15FEB 02MAR 17MAR GIAPR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 120' 0 80, z 40, 01 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND ---- CONTROL ------- SLOTTED WEIR STANDARD WEIR Appendix Figure 8. Number, biomass, and mean weight of southern flounder taken by trawls in each pond. 61 1,200- 800, a, z 400, 01 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 70,000 60,000 50,000 V) 40,000- 30,000- 0 fill M 20,000- 10,000. if 0- 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 1 55J U N30JUN 15JUL 30JUL 3 20' 240- r UJ 160 3@: Ii, I z < 80 0. 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 9. Number, biomass, and mean weight of striped mullet taken by the traps in each experimental pond. 62 3001 200' % % z 100, V@ Ot- 15FEB 02MAR 17MAR 01APR 1 6APR 01 MAY I 6MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 1,500' 10 I- (A1 1,000. V) < 0 500' 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 120, X 80, 0 /.1 Ui z 40, W 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 10. Number, biomass, and mean weight of striped mullet taken by trawls in each pond. 63 6,000 4,000 M z 2,000 01 15FES 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 20,000' 15,000' Ln V) 10,000 t 0 M 5,000' 0i i I I 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 18. UV lit :r 12, z 6 Uj 1 --------------------------- -- C 1 @ I - I - I - - I , - I I I 51FEB 02MAR 17MAP 01APR 16APR 01MA@ 16MAY 31MA@ 15JUN 30JUN 15JUL -70JLL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 11. Number, biomass, and mean weight of white mullet taken ----------------- ------- -- by the traps in each experimental pond. 15' 10, M z 5 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 160, 120, V) V) < 80, 0 M 40' 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 181 12 Ld 01 ISFEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 12. Number, biomass, and mean weight of white mullet taken by trawls in each pond. - - %-4 65 30,000- 20,000- Uj M 0 z 10,000 t 1, 14 01 4-1 1 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 12,000* V) 8,000. V) 0 4,000- M -44 T--r I- I 01 1 15FEB 02MAR 17MAR 01 APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 1.2* T- 0. 8' W ZO.4 < W M 0.011 1 5FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 13. Number, biomass, and mean weight of grass shrimp taken by the traps in each experimental pond. 66 18,000- (Y- 12,000 z 6,000- 0- 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 3,000, 2,000- (A V) M 0 1,000- 0 --------- - 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 0.4' 0-3- 0-2- z ------ 0. 1 0.0- 15FE13 02MAR 17'MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR STANDARD WEIR Appendix Figure 14. Number, biomass, and mean weight of grass shrimp taken by trawls in each pond. 67 10,0001 8,000"0 6,000- M 4,000 3 z 2,00dlo 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 5,0001 4,000- 3,000',@@ V) 2,000 1. 0 1,000 A @A@_4 0 A I . I I ' ' 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2.01 1.5* "i-tk' 1.0 z < 0.5 0-0, 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN '5JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 15. Number, biomass, and mean weight of inland silverside taken by the traps in each experimental pond. 4,000- 3,000- LAJ M 2,000' 1,000 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 3,000- 2,000' W 0 1,000 M 01 1 15FES 02MAR 17MAR 01APR 1 6APR 0 1 MAY 1 WAY 31 MAY 15JUN 30JUN 15JUL 30JUL 1.01 -0.8, T- oO.6 0. 4' z 0.2- 0-0, 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 16. Number, biomass, and mean weight of inland N silverside taken by trawls in each pond. 69 1,500- 1,000, z 500 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 6,000- U 4,000- V) Oil 0 2,000 Cn 0 A2 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN 15JUL 30JUL 18, 0oo 12 W z 6, 0 i 1 5FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 17. Number, biomass, and mean weight of gulf killifish taken by the traps in each experimental pond. 30' 70 ce- 20 3 z 10 --------------------- - - - - - - - - - - - 0i 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 90, 60' V) V) 0 30' M OT --------- I- 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 12 8 z 4, Uj 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 18. Number, biomass, and mean weight of gulf killifish taken by trawls in each pond. 71 1,800 Of W 1,200- Co z 600- IN ;'k A 0 1 1 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2,500- 2,000- V) 1,500- V) 1,000- 0 500' 1"ItI A Iit 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 4 3 r I 0 1. W2 - 't ?-1 z < Ld 01 15FEB 02MAR 17MAR 01APR 16APR ClMAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 19. Number, biomass, and mean weight of sheepshead minnow taken by the traps in each experimental pond. 72 30' 20' % M z 10, 01 15FEB 02MAR 17MAR 01 APR 16APR 01 MAY 1 SMAY 31 MAY 15JUN 30JUN 15JUL 30JUL 20" 15' V) V) 10, 0 M 5 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2.5, 2.0, 1 . 0 z < W 0.5 M 0.0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR STANDARD WEIR Appendix Figure 20. Number, biomass, and mean weight of sheepshead minnow taken by trawls in each pond. 73 300' 200' z 100. 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 400' 300' V) 200" 0 M 100, 0 15FEB 021W 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL' 30JUL 3.5' 3.0' 2.5, 2.0 Ui 3: 1.5 AA z 1.011 11, %1 --A V%V' LLJ 0.5' 0.0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31 MAY I 5JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 21. Number, biomass, a nd mean weight of bay anchovy taken by the traps in each experimental pond. 74 1,600 1,200- LLJ 800* z 400 0 t- r I 15FEB 02MAR 17MAR 01APR 1 6APR 01 MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 400' 300' (A V) < 200 0 100, 01 15FEB 02MAR 17MAR 01APR 16APR 01 MAY 1 GMAY 31 MAY 15JUN 30JUN 15JUL 30JUL 2.0- Uj 1.0- z < 0.5' LLJ 0.0- 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 22. Number, biomass, and mean weight of bay anchovy taken by trawls in each pond. 1,600- 75 1,200- in 800, z 400,', 0 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30.,UL 8001 0 600 0 V) < 400 0 Co 200'IA'l 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 2 z -< - I LWAJ 0' 1 SFEG 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 23. Number, biomass, and mean weight of blue crab (<25mm) taken by the traps in each experimental pond. 76 10, 1rN'@ Li z 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 5 M 0 co of I I I 13FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 3WUN 15JUL =UL ------------- ---------------- - z 15FEB 02MAR 17MAR 01APR ISAPR 01MAY 16MAY 31MAY 15JUN 30JUM 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR - STANDARD WEIR Appendix Figure 24. Number, biomass, and mean weight of blue crab (< 25 mm) taken by trawls in each pond. ,A-1/11 77 1,800- 0 0 1,200, Co Z) z 600 01 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY -31MAY 15JUN 30JUN 15JUL -30JUL 18,000, I-W (A 12,000" V) 0 6,0001 0 --00 F .................7 1 5FEB 02MAR 17MAR 01APR 16APR 01MAY 164AY 31MAY I-5JUN 30JUN 15JIJL 30JUL 140' 105. W 70 z < 35 Uj A_p 0 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 25. Number, biomass, and mean weight of immature female crab taken by the traps in each experimental pond. 100, 75' M 50' z 25, 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN ISJUL 30JUL 1,000 800 (A 600 400@ 0 200. 0 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 75' M 50, 'INN z 25, N < % 01 1 `T. I I I 15FES 02MAR 17MAR 01APR 1-6APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE POND CONTROL ------- SLOTTED WEIR- STANDARD WEIR Appendix Figure 26. Number, biomass, and mean weight of immature female crab taken by trawls in each pond. 79 1,600' 1,200- Co 800, It z 400 01 15FES 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 20,000, It 15,000- A V) it 11 It I I V) 10,000- I it Wit I Iv 0 oil Co It 5,000- 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 300 200 C Z100, t' It 1% to" 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND it ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 27. Number, biomass, and mean weight of male blue crab taken by the traps in each experimental pond. 100, 80' cr_ W 60 z 40' 20' 0i -15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUM =UN 15JUL 30JUL 1,600' 1,200- V) 800' 400 0 TV V v 9 13FED 02MAR 17MAR 01APR 16APR 01MAY IGMAY 31MAY 15JUN 30JUN 15JUL 3WUL 11 UU, A 200' W z 100, < -1 % W % % ---------- 0 1 1 ' I ' ' I ' ' I ' ' I ' I 1 -1 ISFEB 02MAR 17MAR 01APR 16APR olmAy 1"My 31MAy 15jUN 30jUW 15JUL 30JUL DATE POND CONTROL ------- SLOrr WEIR STANDARD WEIR Appendix Figure 28. Number, biomass, and mean weight of male blue crab taken by trawls in each pond. 20' 15' Me 10, z 5 I it 0 15FEB 02MAR 17MAR 01APR 16APR 01MAY 16MAY 31MAY 15JUN 30JUN 15JUL 30JUL 4,000- 3,000- V) < 2,000 0 1,000- ISFEB 02MAR 17MAR 01APR 16APR 01MAY ISMAY .31MAY ISJUN 30JUN 15JUL 30JUL 400- 3 00. M k 200, 111: IV it < 100. it LLJ 01 ISFEB 02MAR 17MAR 01APR 16APR 01MAY ISMAY 31MAY 15JUN 30JUN 15JUL 30JUL DATE SET POND ----- SLOTTED WEIR - STANDARD WEIR Appendix Figure 29. Number, biomass, and mean weight of mature female crab taken by the traps in each experimental pond. 82 Appendix Figure 30. Hourly salinity for both experimental ponds taken at the environmental stations by the Hydrolabs, from 17 January through 30 July 1986. 20 - 15- Io - 25DEC85 a 17 06JAN86oO7 17JAN86s2l 29JAN86ill I OFEW6 a 00 DATE: AND TIME POND ---------- SLorrED WEIR STANDARD WEIR Appendix Figure 30. continued. m1m m mow m mow= m m 20- 15 - 10- -4 5. 01 Z9JAN86ill IOFEBB6sOO 21FEBB6sl4 05MAR86sM DATE: AND TIME:' POND --------- SLOrM WEIR sTMMARD WEIR f I Appendix Figure 30. continued. 20- 15- 10. 5- 0 21FFJMsl4 05MAMmO4 16MAROWIS ZBMAR86sO8 OBAPR86sZl DATE AN D TIME POND --------- SLOTM WEIR STANDARD WEIR Go Appendix Figure 30. continued. 20. 15. 10. 5- 01 OSAPMoZI 2DAPRM s I I 02KAY8601 DATE AND TIME PONI) - --------- sLol"M WEIR STANDARI) WEIR 00 Appendix Figure 30. continued. 20- 15- 10 5- 01 ZOAPR86sll OZMAYB6vOl 13MkY86sl5 25MAY86s04 05JUN86slB DATE AND TIME POND --------- SLOllm WEIR STANDARD WEIR 00 Appendix Figure 30. continued., man 20- lit 10- 01 25MAY86sD4 05JUN86slO 17JUN86sO8 28JUN86o22 I OJLL86 12 DATE AND TIME POND --------- SLOTTED WEIR STANDARD WEIR 0"U" oii@ Appendix Figure 30. continued. 20- 15- 10- 5- 0- 28JEJN86 7-2 IGJUL66tl2 22JUL86:01 OZALIG86il5 DATE AN D T1 M E: POND --------- SLOTTED WEIR STANDARD WEIR 00 Appendix Figure 30. continued. 90 Appendix Figure 31. Hourly water levels taken by the Leupold-Stevens tide gauge at the environmental stations in each experimental pond, from 17 January 1986 through 30 July 1985. MARSH LEVEL L.Lj C= LJA WEIR tz-c LEVEL -15 16JAN86:17 22JAN86:12 28JAN86:07 OIFEB86:22 DATE AND TIME POND --------- SLOTTED WEIR STANDARD WEIR Appendix Figure 31. continued. MARSH LEVEL U.1 X :@:P- L.Lj A WEIR LEVEL -15 29JAN86:11 IOFEB86:00 21FEB86:14 05MAR86:04 DATE AND -17IME: POND --------- SLOTTED WEIR STAMARD WEIR Appendix Figure 31. continued. MARSH LEVEI WEIR LEVEL -15 21FEB86:14 05MAR86tO4 16MAR86:18 28MAR86:08 08APR86:21 DATE AND TIME POND --------- SLOTTF.D WEIR STANDARD WEIR Appendix Figure 31. continued. @ IL lt 1, Lj MARSH L-EVEL- WEIR LEVE -10 -15 28MAR86:08 08APR86321 20APR86:11 02MAY86301 DATE AND TIME POND --------- SLOITIM WEIR STANDARD WEIR Appendix Figure 31. continued. MARSH L-Ev E L- __j WEIR LEVEL -10 -15 20APR86:11 02MAY86;01 13MAY86:15 25MAY86:04 05JUN86tl8 DATE AND TIME: PONI) --------- SLOTTEI) WEIR STMDARD WEIR Appendix Figure 31. continued. MARSH LEVEL WEIR LEVEL -10 -15 25MAY86:04 05JUN86:18 17JUN86:08 28JUN86:22 IOJUL86:12 DATE: AND TIME: POND --------- SLOTTED WEIR STANDARD WEIR Appendix Figure 31. continued. 10- M RSH LEV L W WEIR !@ -5. LEVEL -10- -15 28JUN86:22 ICJUL86%12 22JUL86:01 02AUG86tl5 DATE AND 71ME POND --------- SLOTTED WEIR STANDARD WEIR MARSH Appendix Figure 31. continued. 40' STANDARD WEIR SLOTTED WEIR --------- GRAND. BAYOU 30 "20 CL F- 10* 0 i 5FEB 02MAR 17MAR 01APR 16APR 01 MAY 16MAY 31 MAY 15JUN 30JUN i 5JUL 30JUL DATE Appendix Figure 32. Daily temperature at the levee stations in the experimental ponds and the average daily temperature at the Grand Bayou stations. I I I I I I It I I I 1: I I t t I 11 ------------- I @ I - 3 666-8 00000 8153-1 t t