Semi-Annual Progress Report To National Marine Fisheries Service, NOAA for the period 1 June through 31 December 2005
Brief Project Overview:
The Science Consortium for Ocean Replenishment and Enhancement (SCORE) is a science-based approach to stocking hatchery-reared marine organisms to help rebuild depleted marine fisheries (marine fisheries enhancement). SCORE scientists are conducting research to resolve critical uncertainties about the effectiveness of culture-based marine enhancement as a fishery management tool. It is anticipated that significant progress will be made by SCORE scientists, leading to greater and greater success from marine enhancement programs in the U.S.
As scientific gains are made in understanding the potential, SCORE scientists have partnered with NMFS and regional fishery-management agencies to develop policy and apply fishery-enhancement science to rebuilding depleted coastal stocks. Linkages with local fishing communities provide the cadre of citizens needed to support and expand enhancement as a fishery management strategy. Much of the enhancement technology developed here will be supported by funds generated by contributions and license fees paid by stakeholders and user groups. To fully embrace and use stocking as a marine enhancement management tool, demonstrated success stories are needed in a few key states. SCORE research is planned and coordinated to achieve such successes. Built around the principles of “a responsible approach to marine stock enhancement” (Blankenship and Leber; and see Leber, 2002, 2004), SCORE scientists are conducting key experiments to resolve critical uncertainties about how to control the biological, ecological, and economic effectiveness of marine fisheries enhancement.
SCORE is an R&D initiative conducted by a consortium of national partners. It is a powerful alliance of scientists and fishery managers currently working in the field of marine stock enhancement in the U.S.A., which encourages improved utilization of their expertise and resources. Bringing these scientists and managers together through SCORE allows synergisms to develop that would not occur otherwise.
Multi-Year Contract Period and Relation to this Reporting Period
This Multi-Year contract commenced on July 1, 2004 for the 5-year period ending June 30, 2009. The funding period for this 2nd year of the Multi-Year contract is July 1, 2005 through June 30, 2006. This interim report covers progress made during the period June 1, 2005, through December 31, 2005.
Project Accomplishments:
Mote Marine Laboratory Progress June through December 2005
Aquaculture Research to Develop Rearing Technology for SCORE Species:
Wild Strip Spawning Efforts with Common Snook
The 2005 snook spawning season to produce juvenile snook for stock enhancement research began in late May and continued through September. Due to the results of the 2003 and 2004 spawning seasons, this year’s spawning attempts were conducted on the 2nd and 3rd day after the full and new moon cycles. These days correspond to the previous years’ most successful spawning efforts. Unfortunately, due to the drastic topographical changes that resulted from the 2004 hurricanes and the presence of red tide in and around Sarasota Bay in 2005, many of the historically successful spawning sites have been either inaccessible by boat or contaminated with red tide. A total of 18 spawning attempts were conducted over the snook spawning season. From these spawning efforts a total of over 1,921 adult males and over 178 females were captured. Of these 18 spawning attempts, 11 were successful in yielding an approximate total of 10.3 million eggs that were later stocked for experimental and production trials.
Development of year-round captive spawning protocol for common snook
In mid-August 2005 an attempt was made to transport wild snook broodstock from Charlotte Harbor, FL (2 hours south of Sarasota) to Mote’s main campus for a hormone induced spawning trial. Fish were collected from this area due to the consistently high levels of red tide in Sarasota’s Bay throughout the snook spawning season. From this broodstock collection 5 females (mean weight 2.64 Kg) and 5 males (approximately 1.5 Kg each) were obtained. All of the females were pit tagged, weighed, and injected with human chorionic gonadotropin (HCG) at 500 IU’s/Kg in order to reduce the level of egg regression due to the handling and capture of the fish. Because findings in the literature show that HCG injections do more harm than good to the reproduction capabilities of the male snook; these fish were only pit tagged and were not weighed in order to reduce the stress placed on the fish.
The following day approximately 1.2 million eggs were collected in the egg collectors. These eggs did not show signs of fertilization and were observed to have poor cellular division. In case any of the collected eggs had been fertilized, they were stocked in a single 3.3 m3 production tank. The following day, all eggs had dropped out. Two days later two of the female snook died due to unknown causes. It was later recommended by our broodstock research consultant to inject the remaining 3 female snook with Carp Pituitary Hormone (CPH) at 50 mg/kg and to then check the fish the following week for egg maturation. If the females were then showing signs of maturation, they would be injected with LHRH-a at 200µg/3 kg. Unfortunately, no further egg development was observed after the CPH injection. The remaining 13 fish were quarantined and later moved to a 54,315 L broodstock tank at MAP where they will be monitored for egg development and growth every 4 months.
From late September to mid-October 2005, the Mote maturation and spawning research team met with three expert broodstock consultants to assess the developmental status and prepare a maturation strategy for the captive snook broodstock at MAP. Biopsy results in September and October revealed that some female snook were mature; however, none of the male snook were ready to spawn. In October, one female was implanted with LHRH and 9 males were implanted with methyltestosterone to induce final maturation and spawning. The November sampling revealed that the implanted snook had regressed, which was not surprising since we were far beyond the natural spawning season for snook.
Based on the maturation and spawning plan developed in our October meeting, we began a photoperiod and temperature environmental manipulation using the snook broodstock in the two independent 54,315 L tanks. In late February and/or early March, these fish will be examined for signs of maturation.
Determination of an optimal diet for common snook broodstock
The captive broodstock at MAP are maintained on a diet of shrimp, herring and squid at a ration of 3-4% body weight per day. The fish are monitored for egg development and growth every 4 months. Collaborative work has been discussed with feed companies interested in developing an optimal broodstock diet. Because this diet will focus on the nutritional needs for broodstock to produce viable eggs, analysis of snook eggs for fatty acid and lipid content are needed. Eggs will be collected from both wild broodstock strip-spawned in the wild and cultured broodstock that have spawned. Not only does this study have the potential for finding a species specific diet for broodstock, it also can help Mote’s staff record a historic egg profile for each fish.
Larval Rearing Production Results
All of the larvae from the eggs obtain in the 2005 wild strip-spawning efforts died during the larval experimental and production trials. The majority of the larval production runs dropped out prior to first feeding suggesting an egg quality problem, which may have resulted from the red tide exposure experienced by wild adult broodstock. Only one larval group survived to18 DAH. Experimental results continue to suggest that size of rotifers may be too large as the first food for snook larvae. An experimental trial was conducted that included copepods and rotifers as the first food for larval snook: (1) 75% copepod nauplii and 25% rotifers, 2) 50% copepod nauplii and 50% rotifers, 3) 25% copepod nauplii and 75% rotifers, and 4) 100 % rotifers. Results from this study showed that the 75% copepod nauplii and 25% rotifer diet almost doubled the survival of the larvae when compared to the other treatment regimes examined. Another potential cause of the high larval mortality may have been the high culture temperatures experienced during the larval culture period. Temperatures in the greenhouse hatchery at the main campus were as high as 34oC during June and July 2005. Although the adult and juvenile snook are found at temperatures as high as 34°C in the wild, the effect of these high temperatures on larvae is unknown.
Studies at Mote Marine Laboratory To Develop Effective Release Strategies and Assess The Actual Effectiveness And Potential Impact Of Stock Enhancement:
Evaluate Snook Stock Enhancement Impact in Sarasota Bay and Tampa Bay
Refining release strategies to improve survival of released snook.
We submitted a manuscript entitled “Significance of predator-free enclosures on post-release survival of stocked common snook” by Nathan P. Brennan, Meghan C. Darcy, and Kenneth M. Leber. This manuscript was submitted to Journal of Experimental Marine Biology and Ecology and is in review.
Test of Density-Dependency Effects with Hatchery-Reared Juvenile Snook Released in Critical Nursery Habitats
Proposed work in this area has been completed. We are currently working on analysis and write-up of this study. Results will be distributed when they are completed.
Refining Tag Technology with the Common Snook and Red Drum
Adapting Tag Technology toward Stock Enhancement of the Common Snook
We published this work under the following citation in 2005:
The study of the effects of visible implant elastomer as a tag in fish cornea tissue has been completed. Results from this study are being analyzed and will be reported when completed.
We are investigating the use of acoustic transmitters (Vemco, V8SC1L, 24 mm long) in juvenile (age-0) snook. Both hatchery and wild snook were implanted with transmitters to monitor movement patterns in 2004. We are currently analyzing the results of this study.
Adapting Coded-wire Tags to “Phase-I” Red Drum
A manuscript that describes these activities is in progress.
Feeding Ecology of juvenile snook.
Experiment 1: Determine diel feeding activity of snook ranging from 100-500mm FL in size.
May 26-July 30, 2005: To determine when snook were actively feeding, two 24-hour observation periods were carried out in North and South Creek located in the southern portion of Sarasota Bay. Each 24-hour period was broken-up into 3-8 hour blocks and samples were taken every two hours. Snook were collected using a 73.15 x 3.05 m (240x10 ft.) bag seine with 0.32cm (1/8 in.) mesh with a 3.05 x 3.05 x 3.05 m (10x10x10 ft.) bag. Stomach contents were collected using the pulsed gastric lavage (PGL) technique, as described in Waters et al. (2004), because this allowed for the fish to be released unharmed. This method involves using slightly pressurized water jetted through the esophageal opening to fill the stomach with water while the fish is in a head up position. Then the fish is turned downward at a 45-degree angle allowing any food items to flow out into the collection net. The underbelly is then massaged as the stomach is flushed with a continuous flow of water allowing any remaining food items to be removed. This process is repeated 2-3 times until the stomach is believed to be empty.
A total of 197 snook were caught of which 168 were sampled for stomach contents. Of those sampled, a total of 127 stomach samples were successfully collected. The samples were analyzed using a digestion index ranging from 0-5, with 0 equaling a fresh, undigested sample and 5 equaling a nearly completely digested sample with only bones and/or other hard parts remaining, depending on the prey item. Preliminary analysis suggests that juvenile snook feed primarily after dusk and through the early morning hours, with light to moderate feeding during the daylight hours.
Experiment 2: Describe summer juvenile snook diet in estuaries of southern Sarasota Bay.
July 1-August 19, 2005: During this time period an additional 191 snook were caught and 181 checked for stomach contents. Of those 181 snook sampled an additional 139 stomach samples were collected. These collections were performed at night in the same manner described above. Combined with the previous samples, a total of 266 stomach samples were collected throughout the summer and will be used to describe the diet of juvenile snook in southern Sarasota Bay. Of those 266 samples, 105 were collected from North Creek and 161 from South Creek, respectively.
Fishery Independent Assessment of Adult Habitat
Identify Recruitment of Hatchery Snook to the Adult Populations
We are in the process of producing a publication entitled “Effects of release microhabitat on survival and growth of hatchery-released snook in a Florida estuary”.
Fishery Dependent Sampling of Snook Populations in Sarasota Bay
8TH ANNUAL “SNOOK SHINDIG”
On October 14-15, 2005 the 8th Annual Snook Research Roundup Tournament and Shindig BBQ was held as part of an annual long-term evaluation of snook stockings to the Sarasota fishery. Forty volunteers and research scientists assisted during the tournament in various ways from setting up for the Captain’s meeting, to overnight on-site processing of angler’s snook. Twelve boats, primarily provided and operated by volunteers, acted as mobile weigh-in stations from Venice Inlet to Anna Maria Key. Working crews were equipped with tag detection and fish processing equipment. Personnel from the Stock Enhancement Research Facility provided staff, a research vessel, and processing equipment for the tournament. The Florida Fish and Wildlife Conservation Commission’s Fishery Independent Monitoring Program also provided coded-wire tag wand detectors for this event, as did Northwest Marine Technology, Inc.
During the tournament 195 snook were captured and scanned for tags. Of these, three hatchery-reared snook were from previous releases were recovered. Even with prevalent red tide fish kills over the past year, overall snook catch rates during the tournament appeared unaffected and were still among the highest in tournament history.
We used a point system to calculate the angler’s results. Each inch of snook was counted as one point, a hatchery recaptured snook was worth an additional 75 points, and a wild tagged snook recapture was worth and additional 25 points.
Dave Robinson placed first overall with 27 snook captured worth 604 points. Geoff Smith and Ken Smith placed second and third with 392 and 286 points respectively. David Bronkie captured the largest snook overall at 33 inches total length. Only 7 snook captured (3.6% of the total catch) were legal size, and all of these were captured along the coastline of Sarasota Bay (Northern range of the tournament). Overall 80 snook were captured in the southern Venice area, 73 from the mid-range area from Stickney Bridge to Whitaker Bayou and 42 captured north of Stephens Point in the north Sarasota Bay area (primarily Bowlees Creek).
An evaluation of cannibalism risk in juvenile snook
Results from this study are being analyzed and will be reported on when complete.
Testing the capability of inland snook fisheries
We are investigating the capability of using the common snook in inland pond environments. Forty snook (300-450 mm SL; two age classes) were tagged with individual PIT tags and VIE marks and stocked into a freshwater pond at the Mote Aquaculture Project (MAP). The pond is designed to incorporate thermal refuge, vegetative habitat, structure, and various prey species for snook. An automatic feeder supplements snook diet. Submersed temperature loggers continue to monitor surface and bottom temperatures in the pond. In July 2005 we also set up a remote tag reading antenna in the MAP pond. This prototype system uses half-duplex passive integrated transponder tags that are activated when a tag is within range of a powered antenna. We are in the process of setting up a second antenna along shallow shoreline habitat that will allow us to document differential habitat use of differently sized individuals in the pond. These systems also allow us to monitor survival of the tagged individuals.
In November we tagged 215 snook consisting of three age classes (1, 2, and 3 years old) with half duplex PIT tags. Lengths of each snook were recorded. These snook are being held in the Stock Enhancement Wet Lab Facility until release. Releases will occur in ponds next spring when water temperatures are warmer.
Assist the Florida Fish and Wildlife Conservation Commission (FWC) with Strategic Planning for the FWC Marine Stock Enhancement Program
In line with the short and long-term objectives of strategic planning for the Fish and Wildlife Conservation Commission’s marine stock enhancement program, several steps have been made toward (1) improving the effectiveness of FWC’s marine stock enhancement program, (2) adapting and refining the aspects of a “Responsible Approach to Marine Stock Enhancement” (Blankenship and Leber, 1995) that have not yet been fully implemented in Florida, and (3) identifying and prioritizing potential marine fish species for stock enhancement in Florida.
- Dr. Ken Leber (Mote Marine Laboratory) has been working closely with the Florida Fish and Wildlife Conservation Commission’s Stock Enhancement program as a chief advisor and co-leader in strategic planning and research planning in this program.
- Dr. Leber has continued to work closely with the state in developing and implementing the pilot release experiments to evaluate the effectiveness of releasing juvenile red drum in Tampa Bay to boost red drum population size there (Project Tampa Bay).
In addition to managing collaborative aspects of this project at Mote Marine Laboratory, Dr. Leber participated in several planning meetings with FWC staff during this grant period. These included meeting with the Director of the Marine Research Section and of the FWC Stock Enhancement program on September 23, to discuss future research needs and again on January 17th, at FWC’s Fish and Wildlife Research Institute (FWRI). Leber was an invited speaker at FWC’s workshop on 28 September 2005 on Florida Bass stock enhancement, where Leber presented an overview of the Responsible Approach concept and application. Leber also assisted FWRI in October 2005 with the planning and conduct of a semi-annual meeting with the Florida Marine Stock Enhancement Advisory Board, a stakeholder group organized by FWC to assist in planning future goals, objectives and activities of the FWC Marine Stock Enhancement Program. On 2 November 2005, Leber participated as a panel member of the FWC Genetics Committee to finalize Florida’s genetic protocols for hatchery stocking initiatives throughout the state of Florida. The genetic protocols are established to minimize genetic hazards to wild stocks from stocking hatchery fish. These genetic protocols are to be incorporated into the state’s permitting system for scientific and other activities requiring a collecting permit. A stocking permit is also required under Florida’s system.
UNH Progress June through December 2005
The long-term goal of our winter flounder stock enhancement program is to accelerate recovery of the fishery by increasing spawning stock biomass. To meet this goal, we have developed a multidimensional research program designed to produce large numbers of high quality juveniles, to optimize release strategies, and to understand how habitat attributes affect movement and sexual differentiation of juvenile winter flounder. Elements of the program addressed in this reporting period have included:
Juvenile Fish Production:
We produced approximately 10,000 winter flounder from a wild-caught broodstock at the Coastal Marine Laboratory (CML). These fish were used for the 2005 acclimation cage/predator study. In addition, we maintained fish from the 2004 hatchery production. These one-year old flounder are being used for the telemetry studies.
Acclimation Cages/Predator Study:
Juvenile flatfish are vulnerable to a suite of predators, including many decapod crustaceans. For juvenile winter flounder, predation by green crabs Carcinus maenas is of special concern (Fairchild & Howell 2000). In a field study done prior to the 2004 release of fish, we found that average green crab density at the release site was 0.6 crabs/50 m2. This density was not significantly different than adjacent areas. Our acclimation cages, stocked with cultured flounder, were then placed at the site so that the fish could adjust to their new environment for 2 days, and then be released from the cages. Within 4 days after the release, crab density increased 7 fold to 4.3 crabs/50 m2 in the immediate area. Crab density returned to pre-release densities quickly thereafter, but cultured winter flounder density also decreased quickly. No cultured flounder were recaptured outside of the immediate release site despite frequent sampling. The sharp increase in crab density, combined with the sharp decrease in flounder, leads us to hypothesize that crabs may be attracted to, and aggregate around, the acclimation cages containing the fish, and that crab predation may have been responsible for the decrease in the cultured flounder density. Thus although acclimation cages are a necessary tool that allows the stocked fish to adjust to their new environment, they also may be a detriment if they attract predators to the site.
To determine if green crabs are attracted to the acclimation cages, a study was conducted in August 2005 at the release site. Crab densities were determined by trawl surveys for 2 days. Following this, four acclimation cages were placed on the bottom at the release site. Two replicates contained flounder while two were empty (control). Surveys of crab density (#crabs/m2) within 5m of each cage were conducted daily for 3 days by SCUBA. Results showed that after one day, crab abundance was significantly (t-test, p < 0.01) higher on cages containing fish than on empty cages, proving that acclimation cages containing flounder do attract green crabs.
To determine if acclimation cages, even in the absence of fish within them, attract crabs because they provide structural relief in an otherwise relatively featureless environment, a second field study was conducted in September 2005. In this, a second site (control) was established 250m downriver from the release site. At both sites, crab densities were determined by trawl surveys for 2 days. Four empty acclimation cages were deployed at the release site while no cages were deployed at the control site. At the release site, surveys of crab density (#crabs/m2) within 5m of each cage were conducted daily for 3 days by SCUBA, while at the control site, trawl surveys were continued. Results showed that within 30 minutes of cage deployment, crab densities significantly increased in the release area (t-test, p < 0.01) and continued to increase each day indicating that green crabs are attracted to the empty acclimation cages.
Although cages are necessary for acclimating cultured flounder (Fairchild and Howell 2004; Sulikowski et al. 2005), they also are detrimental by attracting predators to the release site. Modification of the release strategy is necessary to offset this problem and alternate release strategies are being investigated. For example, in addition to our “standard” release protocol, we also will release acclimated flounder into a secondary release site where crabs have not aggregated and then we will compare crab density at both sites. The completion of this objective will be done next summer.
The results from these acclimation cages studies will be presented in May 2006 in Florence, Italy at Aqua 2006.
Temporal and spatial distribution of juvenile wild and cultured winter flounder in the estuary:
The objective of this study is to identify the areas within the estuary where juvenile fish are found, to characterize their habitat, and to study their temporal and spatial use of the estuary. In addition, cultured and wild juvenile movements will be compared. To accomplish this goal, both wild and cultured juvenile winter flounder were anesthetized, fitted with acoustic tags (VEMCO V7-2L-R256 coded pinger tags), and released. Each acoustic transmitter emits a distinctive coded pulse (frequency 69 khz) that is detected by a hydrophone, thereby allowing the fish’s location to be accurately determined, and the fish’s movements to be tracked over time.
To ensure that the tag (17x7 mm, 0.5 grams in water) did not interfere with the fish’s swimming abilities, a laboratory experiment was conducted in June at the CML in a 2 m diameter round fiberglass tank containing a 2 cm layer of sand on the bottom. Three cultured fish (mean size = 33g, 117mm) were fitted with dummy tags in the following way. A 15 mm length of Tygon™ tubing was cut lengthwise and 2 holes on each side of the cut were made by heating a needle and melting the tubing. Then the tag was glued to the inside of the tube with Marine Amazing Goop™ and allowed to cure for 24 hrs. The final product added 0.3 g to the tag weight but for an average one-year old, 22.9 g (+4.7g) cultured juvenile fish, the total tag configuration is 3.6% (+0.7) of the fish’s weight in water. This tag arrangement ensures that the tag can be sewn securely to the fish.
The fish were anesthetized with MS-222 (0.5g/l) for 2 min, and then each tag was sutured (2-0 Dermalon blue) to a fish just above the lateral line and laying perpendicular to the fish’s axis. Tagged fish were allowed to recover in a 1 m diameter tank for 48 hrs. The 3 tagged cultured fish (mean size = 33g, 117mm), along with 3 untagged cultured fish (mean size = 22g, 108mm) and 3 wild caught untagged fish (mean size = 15g, 118mm), were placed in the tank and filmed from above for 48 hrs with time lapse video. At the end of 2 days, while still filming, each fish was gently prodded to elicit a burst swimming episode. The VHS tapes were analyzed so that for each fish the total distance moved in 48 hrs, and the swimming speed and distance moved when prodded were calculated. Means were generated for comparing the movements of tagged cultured, untagged cultured, and untagged wild fish. Tagged cultured fish did move further (ANOVA, p<0.01) than untagged cultured fish. It is possible that the tags were not sutured tightly enough to the fish and flapped against the fish. This movement could have spooked the fish which would explain the additional distance swum. No differences were observed in either the burying behavior (ANOVA, p=0.37), burst swimming speeds (ANOVA, p=0.07), or the amount of moves (ANOVA, p=0.50) made by tagged and untagged cultured fish. Therefore, we assumed that, overall, the tag location and mode of attachment did not adversely affect the flounder and we initiated the field work.
Simultaneous releases of cultured and wild one year old winter flounder occurred in the Hampton-Seabrook Estuary, New Hampshire, USA. Wild fish were caught by beam trawl at the release site (Hampton River) and brought back to the CML where they and the cultured fish were fitted with acoustic tags. All fish were released 48 hours later by gently placing them into the river. Tracking began one hour after the fish were released and continued daily until either the fish could not be found or we suspected that the tag died. Fish were located manually using an omnidirectional and a directional handheld hydrophone. When a fish was located, the position (latitude, longitude), depth, and tidal stage were recorded. Using a Niskin sampling bottle, temperature, salinity, and dissolved oxygen were measured from the bottom. In addition, a core was taken with a grab sampler for sediment composition analysis. Fish location data were analyzed using ArcView 3.3 software.
The first release occurred on 13 July 2005 when 3 cultured fish (30 + 3 g; 122 + 3 mm) and 3 wild fish (15 + 2 g; 118 + 2 mm) were released. Unfortunately, immediately after their release, the directional hydrophone broke and was not replaced by VEMCO for 5 weeks. During that time, the fish only could be tracked by the omnidirectional hydrophone which could not pinpoint fish locations. Nonetheless, we were able to get general locations of the fish for 64 days. Though data analysis was not possible without exact positions, we observed that the fish generally remained in the release area.
For the second release, 2 cultured (47.3 + 0.4 g; 137 + 7 mm) and 2 wild (39.6 + 0.8 g; 147 + 1 mm) fish were tagged and released on 23 August 2005 and tracked daily for 78 days. Within the first 2 days, cultured fish emigrated approximately 1000 m out of the release site. After this initial movement, however, the mean daily movement of the wild fish (22 + 22 m) was significantly (p < 0.01) greater than that of the cultured fish (10 + 14 m). This difference also was detected by kernal analysis of the home ranges. In the 95% probability area, cultured fish maintained a smaller home range than wild fish (wild = 3948 m2; cultured = 1185 m2; p = 0.01). However, there were no significant differences in the 50% probability area (wild = 419 m2; cultured = 225 m2; p = 0.14), nor in the overall area (wild = 2762 m2; cultured = 798 m2; p = 0.10) or perimeter (wild = 208 m; cultured = 129 m; p = 0.14) of the home ranges as computed by minimum convex polygon analysis. Habitat use by cultured fish was very similar to that of wild fish. There were no differences in dissolved oxygen (p=0.64) or salinity (p=0.67). Cultured fish were found in water 1 m deeper (p<0.01), and, thus, 1 °C cooler (p=0.03) on average than wild fish. Sediment composition analyses have not been completed but we suspect there will be no differences.
In order to describe fine-scale movements of juvenile winter flounder, a VEMCO VRAP system which automatically tracks tagged fish movements within a triangular array of buoys was deployed in the release area. This third release on 28 November 2005 consisted of 2 wild fish (44.3 + 36.6 g; 151 + 49 mm) and 6 cultured fish (60.3 + 31.6 g; 153 + 18 mm), 2 of which had been acclimated in a cage for 48 hours. As of 31 December 2005, this group of fish is still being tracked. Analyses will reveal if there is a relationship between fish movements and tidal stage, and also if acclimating cultured flounder in cages at the release site reduces their initial movements.
Results from these tagging studies will be presented in May 2006 in Florence, Italy at Aqua 2006 and in September 2006 in Lake Placid, NY at the annual meeting of the American Fisheries Society.
Sex ratio of juvenile winter flounder:
We have shown that the sex ratio was significantly different than 1:1 in the 2003 cultured winter flounder population (males dominate 2.5:1)(Fairchild et al., In Review), and we know from studies with other flounders that water temperature can affect gender during differentiation. Because winter flounder spawn and develop throughout estuaries, which often have spatially different temperature regimes within them, it is possible that the sex ratio of wild fish varies from one part of an estuary to another, dependent on which part of the estuary they develop in. To investigate this, 3 sites in the Great Bay Estuary that differ in temperature were chosen for this study. Because winter flounder spawn in March/April, and an individual’s gender is determined at <41mm TL (Fairchild et al., In Review), we assumed the gender of fish we collected would have been influenced by the thermal regime they experienced from hatching through gonadal differentiation. Temperature recorders were deployed to document temperature and a total of 89 one-year old juvenile winter flounder were collected by trawl in early June (age 1 fish) and 25 in late October (young-of-the-year). All fish were measured, euthanized with an overdose of MS-222, and preserved in Davidson’s modified fixative. Gonads were dissected out of each fish, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Slides were numerically coded and examined by three viewers in a blind test to determine gender based on structures and cells associated with gonadal tissue. Fish were scored male, female, unknown (gonadal tissue visible but unidentifiable to sex), or missed (no gonadal tissue present on slide). Although sex ratio data are being analyzed still using Chi-square goodness of fit, it appears that the sex ratio of fish at all sites in both spring and fall is 1:1. These results, along with the findings from the cultured flounder sex ratio and sexual differentiation study from last year, were presented in Norway in August at the meeting of the European Aquaculture Society.
We also continued the sex ratio research on cultured juvenile winter flounder by (1) identifying sex of other year classes of cultured fish and (2) by manipulating juvenile rearing temperatures. From the 2004 and 2005 cultured populations, a total of 149 and 50 fish were sampled, respectively, for sex identification. These fish were processed and are being analyzed in the same manner as the wild fish. In addition, fish rearing temperatures are being analyzed to determine if any thermal differences existed between years which might explain sex ratio differences.
To determine if winter flounder exhibit temperature-dependent sex determination (TSD), a temperature manipulation experiment was conducted in the laboratory with young-of-the-year cultured fish. Three replicates of 3 temperature treatments (5, 10, 15°C) were set up in climate-controlled rooms at the UNH. Experimental units consisted of glass aquaria filled with 40 liters of filtered, UV sterilized sea water. Each of these static systems contained a carbon filter, aerator, gross particulate sponge filter, and was illuminated from above (24L:0D). Fifty cultured fish (59 dph; mean TL 16.6mm) were stocked into each tank on June 20, 2005. Fish were monitored daily for 72, 123, and 86 days for the 5, 10, and 15°C treatments, respectively. Daily protocol included feeding (Gemma 300-500microns), and measuring water temperature, dissolved oxygen, salinity, and total ammonia. Twenty liters of water in each aquarium were changed approximately weekly, and total ammonia levels never exceeded 1ppm. Too few fish survived in the 5°C treatment to generate meaningful results. In the other 2 treatments, once the fish were > 41 mm TL and gonadal differentiation was complete (Fairchild et al., in review), all fish were processed. The data are being analyzed using Chi-square goodness of fit and these preliminary results should inform us if winter flounder gonadal differentiation is affected by these temperatures.
Northwest Fisheries Science Center Progress June through December 2005
Manage Fish Health and Disease:
Development of improved diets for larval marine fish
Study A) To evaluate the ability of FTDM to support growth and survival of larval Pacific rockfish.
Additional work continued on scaling up production and testing methods for the fractionated trypsin digest micro-diet (FTDM). During the period staff set up an additional larval rearing system with 12 tanks for larval fish feeding studies, and began to renovate an old wet lab for scaled up microparticulate feed preparation. A pilot trial using rockfish and Atlantic cod (Gadus morhua) in the new system was conducted however we ran out of feed and larvae prior to fully completing this task. This study will be completed in early 2006 when larva once again become available.
Continuing work on micro-particulate feeds and formulations was on-going during the period.
Study B) To refine methods to determine apparent protein digestion and absorption efficiency of FTDM for cod larvae.
Due to a lack of Pacific Cod (Gadus macrocephalus) broodstock showing up on the spawning grounds in 2005, and the resulting lack of larvae this study was completed using Atlantic Cod purchased from a hatchery on the east coast. After several refinements to the method to determine the apparent digestibility of protein in larval feeds in July 2005, we successively conducted a feeding trial in August with 8-week-old Atlantic cod larvae and determined the Apparent Digestibility Coefficients (ADC) of protein for a live feed and a microbound diet. The live feed used was Artemia nauplii marked with dysprosium oxide. The microbound diet (FTDM see Study A) was developed in our laboratory from a fraction of trypsin digested cod muscle and was marked with yttrium oxide. In addition to ADCs, we were able to determine the amount of feed ingested by larvae actively feeding on a single meal of each diet and we measured the amount of feed passed at 6 hours after ingestion. During the later part of 2005, we completed our analyses of samples from the experiment and began preparation of a manuscript. The current plan is to complete the manuscript and submit it to a refereed scientific journal in the first half of 2006
Three manuscripts describing previous SCORE work were written during the period, and two presentations were given at international meetings. Details are contained in the Presentation and Publication section below.
Describe Life History Patterns and Ecological Interactions
1. Lingcod
Study A) Continue to monitor adult lingcod released in FY04
In FY 2004, 14 acoustically tagged adult lingcod were released at two locations in southern Puget Sound. Tracking of these at-large fish continued in FY2005 until the end of the tag life. A draft report; “Survival, site fidelity and movement behavior of acoustically tagged hatchery lingcod released in south Puget Sound” was produced, however data analysis is still at a superficial level. Completion of this task and writing up the results for publication will resume after the SCORE sponsored training on analysis of data from acoustic tagging studies.
Study B) Determine whether surgically implanted acoustic tags affect the survival, growth and spawning of adult lingcod held in captivity.
We noticed delayed mortality in groups of juvenile Pacific cod destine for release (see below). Since there was an immediate need for this information prior to a Pacific cod release experiment we decided to change this study to use juvenile Pacific cod instead of lingcod. Given the funding cuts in FY06, it is unlikely that we will attempt this study with adult lingcod anytime soon.
The first Pacific cod destine for release were tagged on March 30 2005. We initially tagged 19 individuals and kept the fish on chilled water at 8-8.5 °C. As mortalities occurred new fish were tagged. Initially, mortalities averaged about one fish per week up to about 40 days post initial tagging. At 40 days post tagging mortality increased significantly and the cause could not be determined. This was significant since in previous trials we (and others) had assumed that fish sill alive after two weeks from tagging were unlikely to experience tagging related mortality. Interestingly, untagged fish reared under the same conditions experienced little or no mortality during this period.
On 06 June 2005, we initiated this tag-effects study to determine whether the tagging procedure (i.e., anesthetization, incision and sutures) or implantation of the tag itself was causing the mortality described above.
We divided the fish into 4 treatment groups for this study. The treatments were; 1) previously tagged fish, 2) newly tagged fish, 3) Sham tagged, and 4) untagged controls. All fish were anesthetized with Tricaine methanesulfonate at a dose of 100 mg/l. Surgerical methods followed the protocols outlined in Ladoucer et al. (2005). Three fish from each treatment group were stocked out into each of three replicate 12 ft diameter tanks. Recirculated chilled seawater at 7.5 °C was supplied to the tanks at a rate of 12 gpm. Feed was supplied to the fish in excess at a feed rate of 5-7% BW/day. The study lasted 7 weeks, ending on 25 July 05. Results of this study are given in the table below.
|
Treatment1
Pre tag3 Tag4 Sham Control |
Growth (% BWG/day2)
0.29 + 0.13 (n=7) 0.59 + 0.26 (n=8) 0.49 + 0.16 (n=9) 0.52 + 0.17 (n=7) |
Survival (%)
77.78 + 19.25 (n=9) 88.89 + 19.25 (n=9) 100 + 0.00 (n=9) 77.78 + 38.49 (n=9) |
2 Percent body weight gain per day.
3 Each tank (5,6,7) had two fish tagged on 5/16/05. Tanks 5&7 had one fish each tagged on 3/30/05. Tank 6 had one fish tagged on 5/9/05.
4 Tagged on 6/6/05.
1 Three fish per treatment were placed in each 12tf diameter tank. Three replicate tanks were used.
2 Percent body weight gain per day.
3 Each tank (5,6,7) had two fish tagged on 5/16/05. Tanks 5&7 had one fish each tagged on 3/30/05. Tank 6 had one fish tagged on 5/9/05.
4 Tagged on 6/6/05.
Study C: Collect lingcod eggs and produce juveniles for FY06.
Approximately 1500 juvenile lingcod were produced in winter 05. Unfortunately, the majority of fish were killed when river otters found a way into the net-pens containing the majority of the lingcod. A small number (300) of fish that had been moved to a tank on shore survived can be used for small scale studies and replacement broodstock. Given the sever cuts to the SCORE budget in FY06, this task would have been scaled back anyway. No lingcod for release will be cultured in winter 06 due to funding cuts.
2. Pacific cod
Studies on Pacific cod Juveniles during the period had to be modified or cancelled because no adult spawning cod were collected during the winter of 2005. This was despite a similar sampling effort as in previous years. The spawning stock of Pacific cod that we are working on (Puget Sound) is at historic lows. Even in the past using trawls and hook and line sampling methods we have only been able to obtain small numbers of adults (less than 20/yr). Fall and winter 2004-2005 was warm and dry. This might have impacted the number of fish that were in the spawning stock to the point where spawning for the most part did not occur in 2005. We will be increasing our sampling efforts in 2006.
Study A: Investigate the effects of release location on release-site fidelity, migration patterns, and inferred survival.
Methods
Release locations:
Each release location was located at well defined vegetation transitions between continuous eelgrass (Zostera marina) beds and other vegetation types which were first located in The Bainbridge Island Nearshore Habitat Characterization and then verified by underwater video observation. One release site was located at the north end of Bainbridge Island ~ 700 m south east of the Agate Pass Bridge (N 47 42.389, W122 33.955). The vegetation north of the release site was a continuous eelgrass and the area south of it was predominately Laminaria , Ulva , Fucus with sparse patches of Zostera. The second site was located ~ 600 m south west of Point Monroe on the northern tip of Bainbridge Island (N47 42.474, W122 31.223). The vegetation east of the release site was a continuous a eelgrass bed and the area northwest of site was continuous Ulva bed changing to Ulva and Laminaria mixed with bare patches of rock, sand and shell further north west of the release site.
Nineteen Pacific cod implanted with acoustic transmitters (see tag effects study above) were loaded into an aerated holding tank and transported by boat to the two release locations (Agate Pass and Pt. Monroe; Figure 1). All 19 fish were transported in 14.8 C water on 16 August 2005 between 1431 and 1446 hrs and released into 15.5 C water at the Agate Pass site (1.5 m depth) and 15.2 C (1.5 m depth) at the Pt. Monroe site. Both sites had a sharp transition between eelgrass (Zostrea marina) and brown algae (Fucus sp.) vegetation in the nearshore environment.
At each release site, one acoustic receiver was placed near shore in the eelgrass habitat and one approximately 500 m away in the adjacent non-eelgrass habitat. Each receiver was capable of detecting tags within an approximate 500 m diameter. The tags were configured to randomly transmit an acoustic ‘ping’ every 60 to180 seconds for approximately 540 days after release. Automated Hobo temperature recorders (Onset Corporation) were deployed with the acoustic receivers to record temperature every 2 hours. Additional VR2 receivers were placed in other nearby locations to track movements of cod through Rich Passage, Agate Pass, and Colvos Pass (Figure 1).
Active detection of acoustically tagged Pacific cod was conducted using a boat-mounted Vemco VR28 ultrasonic receiver up to 48 hours after release of the 19 cod. The receiver was towed approximately 15.1 km on 17 August and 3.6 km on 18 August at the Manzanita site, and 5.4 km on 17 August and 16.3 km on 18 August at the Point Monroe site.
The receivers and temperature logger were recovered at the Point Monroe and Agate Pass sites on 7 September, from Rich Passage on 2 December, and from Clovos Pass on 9 December.
Results
The Pacific cod implanted with acoustic transmitters remained in the nearshore environment, within range of the VR2 receivers, for highly variable durations. At the Agate Pass site, two of the fish were last detected on the receivers not more than 30 hours after release. The longest duration any one fish was detected within range of the receivers was 45 d (Table 2). At the Pt. Monroe site, three fish remained less than 48 hours within range of the receivers, and the longest ‘residence’ time was 30 d (Table 2).
Pacific cod released at the Agate Pass site tended to spend more time near the receiver placed in eelgrass habitat than non-eelgrass habitat, but fish at the Pt. Monroe site did not exhibit a similar trend (Table 3). Data collected on the VR28 receiver suggested a more offshore movement of cod at the Pt. Monroe site than at the Agate Pass site (Figure 3).
Study B: Determine whether surgically implanted acoustic tags affect the vulnerability of juvenile Pacific Cod to predation.
Given the lack of Juvenile cod available this study was modified to use yearling (04 cohort) cod and is described above under lingcod, study B. Due to the lack of animals, no predation study was conducted.
Study C: Describe patterns of habitat use by cultured and wild juvenile Pacific cod in Puget Sound, and establish a pre-supplementation database to determine how to release cultured and wild fish.
Nearshore beach seining efforts conducted by the City of Bainbridge Island, in collaboration with the Suquamish Tribe, have resulted in capture of a total of 15 juvenile Pacific cod between 2002 and 2004 (P. Namtvedt Best, City of Bainbridge Island, Pers. comm.). Twelve of the 15 fish were captured in nearshore habitats containing eelgrass as the primary vegetation and 2 were caught in habitats with Ulva as the primary and eelgrass as the secondary vegetation. No Pacific cod were captured in Fucus habitats or non-vegetated sites. The majority of fish (12 of 15) were captured at a site that contained eelgrass, sandy/gritty substrate, and a gentle (<5%) slope. These data provide a starting point for locating important nursery habitats for juvenile Pacific cod.
We began assisting with the beach seining efforts in December 2005, and plan to continue working with the City of Bainbridge Island, Suquamish Tribe, and the Kitsap Nearshore Group to sample Pacific cod in the nearshore environment. The few number of collected fish over the past 3 years suggests that cultured fish may have to be used as surrogates for identifying important juvenile rearing habitat. Efforts in 2006 will attempt to identify additional nearshore habitats with similar features that support Pacific cod.
Study D: Assist in a study to determine broad range genetic structure of Pacific Cod.
No new samples were collected during the reporting period. If more adult Pacific Cod are obtained in the winter of 06, then these samples will be added to the previous samples for the genetic study being conducted by scientists at the Alaska Fisheries Science Center.
Presentations during period:
Cook, M., R. Johnson and M. B. Rust. Development of a Method For Determining Consumption in Marine Fish Larvae.
Poster (chosen "topic of special interest") LARVI 05, Sept 5-9, 2005, Ghent, Belgium.
Menasveta, P. M. Izquierdo and M. B. Rust. Academic Impressions of LARVI 05 and the state of the art. LARVI 05, Sept 5-9, 2005, Ghent, Belgium.
Nicklason, P. Real time measurement of leaching in microparticulate diets. Fish Feed and Nutrition Conference, Sept. 2005 Ensenada, Mexico
Manuscripts published, completed or submitted during period:
Cook, M A. and M. B. Rust. (2005) Lingcod research continues in the Pacific Northwest. Global Aquaculture Advocate. 2:2005, pp 79-80.
Cook, M. A., Guthrie, K. M., Plesha, P. and M. B. Rust. (In Press) Effects of Temperature and Salinity on the Hatching and Development of Lingcod, Ophiodon elongatus Girard, Embryos, Aquaculture Research
M.A. Cook, R.B. Johnson, P. Nicklason, H. Barnett and M.B. Rust. Marking Live Feeds With Inert Metal Oxides For Fish Larvae Feeding and Nutrition Studies. Submitted to Aquaculture Research.
Nicklason, P. Real time measurement of leaching in microparticulate feeds. Ready to submit.
References Cited
Blankenship, H. L. and K. M. Leber. 1995. A responsible approach to marine stock enhance-ment. In Uses and effects of cultured fishes in aquatic ecosystems. American Fisheries Society Sympo-sium 15:165-175.
Fairchild E.A. and W.H. Howell. 2000. Predator-prey size relationship between Pseudopleuronectes americanus and Carcinus maenas. Journal of Sea Research 44(1):81-90
Fairchild and Howell. 2004. Factors affecting the post-release survival of cultured juvenile Pseudopleuronectes americanus. Journal of Fish Biology 65:69-87.
Ladoucer, A.R., Jacobs, M.C., Winchell, P.M. 2005. Kintama Research Corporation Acoustic Tag Surgery Guide. Draft March 2005.
Leber, K. M. 2004. Marine Stock Enhancement in the USA: Status, trends and needs. Pp 11-24 In Leber, K.M., S. Kitada, T. Svåsand and H.L. Blankenship (eds) Stock Enhancement and Sea Ranching: Developments, Pitfalls and Opportunities. 2nd Edition. Blackwell Publishing, Oxford. 562 pp.
Leber, K. M. 2002. Advances in marine stock enhancement: shifting emphasis to theory and accountability. Pp 79-90 In Stickney, R. R. and J. P. McVey (Eds) Responsible Marine Aquaculture CABI Publishing, New York.
Sulikowski, J. A., D. A. Fairchild, N. Rennels, W. H. Howell and P. C. E. Tsang. 2005. The effects of tagging transport on stress in juvenile winter flounder. Journal of the World Aquaculture Society 36(1):148-156.