Search

A 9-week feeding trial was conducted with juvenile red drum, Sciaenops ocellatus, to evaluate the use of soy oil as a fish oil replacement. Three primary protein sources (fishmeal - FM, soybean meal - SBM, and soy protein concentrate - SPC) were utilized with 100% fish oil (FM, SBM, SPC), 75% fish oil (SBM, SPC), or 50% fish oil (FM, SBM, SPC) as the lipid source. Traditional growth and performance metrics (specific growth rate, feed consumption, feed conversion ratio) were tracked and tissue samples (liver, muscle, plasma, adipose, and brain) were collected for gas chromatography-based fatty acid profiling. Ten lipid metabolism related genes were analyzed for potential expression differences between dietary treatments in liver and muscle tissues and whole body and fillet tissues were sampled for proximate composition analyses. Forty- four fatty acids were measured by gas chromatography-flame ionization detector (GC-FID) and evaluated with principle component analysis and ANOVA to understand the dietary influence on lipid metabolism and health. Significant differences in growth rate were observed with the SBM 50% fish oil diet outperforming the FM 100% fish oil reference diet. All other soy protein-based diets performed statistically equivalent to both FM reference diets (100% and 50% fish oil) in regard to growth, however all soy protein-based formulations had significantly lower feed conversion ratios than the fishmeal-based references (p < .001). Gene expression differences were not significant in most cases, however often trended similarly as the observed performance. Fatty acid profiles differed as a function of oil source, with no apparent influence by protein source, with C18:2n-6 (linoleic acid) being-the primary differentiator. Overall, the six soy protein, fishmeal-free formulations performed equivalently or better than the fishmeal references with up to 50% of fish oil replaced by soybean oil.

We investigated changes in the metabolome in juvenile red drum (Sciaenops ocellatus) induced by increasing amounts of soybean meal (0% to 60%) in extruded, fishmeal-free diets using a nuclear magnetic resonance spectroscopy (NMR)-based metabolomics approach in a 12-week feeding trial. All of the diets were composed of ≈40% total crude protein, ≈11% total crude lipid and were energetically balanced. A fishmeal-containing, commercial extruded diet was used as a control diet throughout the trial. Each week, liver, muscle, intestine and plasma samples were collected and analyzed by NMR to provide a "snapshot" of the metabolome at different time points. Results indicate significant time-dependence of the metabolic profiles in various tissues with stable metabolomic profiles forming after about 9-weeks on the experimental diets. We identify a previously unexploited biomarker of potential dietary stress (N‑formimino‑l‑glutamate (FIGLU)) in the fish that may prove to be useful for optimization of alternative diet formulations.

The South Carolina Department of Natural Resources (SCDNR) began stocking red drum, Sciaenops ocellatus (Linnaeus), in 1989 to augment the abundance of juveniles available for recreational harvest in South Carolina estuaries. While stock enhancement can help supplement wild populations under high fishing pressure, releasing hatchery‐raised fish into the wild also presents the risk of decreased genetic diversity. An individual‐based model (IBM) was developed to forecast the genetic influences of stocking on the wild spawning population to inform responsible stocking strategies. Model results indicated the SCDNR red drum stock enhancement programme should maintain mean contributions of stocked fish no greater than 30% per year class over a 45‐year stocking period, coupled with at least 10 effective breeders in the hatchery replaced annually, to maintain current levels of genetic diversity estimated in the wild population. The IBM is a useful tool for hatchery managers to guide responsible stock enhancement.

The South Carolina Department of Natural Resources began a stock enhancement research program for red drum, Sciaenops ocellatus, as a possible management strategy for augmenting the availability of juveniles for recreational harvest in South Carolina estuaries. Between 1999 and 2011, approximately 6 million juveniles and 260 million larvae were stocked into the Charleston Harbor (CH) estuary, and proportions of stocked fish were found through standardized sampling as high as 49.6% within a subadult year-class and up to 12% within the spatially separate spawning population. This study evaluated the genetic influences of stocking on the spawning population, using microsatellite loci, and examined any changes in genetic diversity metrics over the course of the stock enhancement program. Percent contribution of stocked fish among subadult and adult collections was compared against measures of genetic diversity. No statistically significant correlations were found among genetic diversity metrics, suggesting that responsible stocking of red drum as small juveniles has not altered the genetic diversity of adults spawning offshore the CH. Life-history characteristics likely play a large role in mitigating changes in genetic diversity, despite high contributions of stocked fish in some years, because red drum exhibit a long adult life span and benefit from overlapping generations.

Telomere length measurements are becoming increasingly popular in biology as a non-lethal tool for estimating organisms’ biological conditions. One particularly appealing application of telomere length measurements for conservation biologists is genetic age estimation. Most age estimation methods require animals to be sacrificed followed by the dissection and sectioning of calcified structures. Because telomeres degrade over time, telomere lengths may provide non-lethal and minimally invasive tool for estimating age. Furthermore, telomere length may also be useful for predicting longevity and fitness. Traditionally, telomere lengths have been measured using terminal restriction fragment (TRF) methodology; however, there is no one standard laboratory procedure to estimate the size of these fragments, and few studies supply repeatability data for the respective methods. While TRF telomere length assays are applicable to all organisms with known telomere repeat motif sequences, inconsistencies in TRF methodology include template DNA treatment, restriction enzymes used, gel electrophoresis methods, and probe/detection methods. Here we present a study documenting repeatability data for a specific laboratory procedure for estimating telomere length using two common restriction enzymes, denaturing pulsed field gel electrophoresis, and a chemiluminescent detection system for three replicates of 16 individual red drum collected in South Carolina. The data were analyzed following traditional methods using an average across the entire TRF distribution, which represents all TRF lengths found in the sample; and following non-traditional methods, where only a subsample of the TRF distributions are analyzed. Our results demonstrate a strong correlation among average TRF lengths between replicates while analyzing the entire TRF distribution; however, our results show a decreasing trend of consistency between replicates as smaller portions of the TRF distribution were analyzed. These results suggest our method provides a repeatable estimate of average TRF length in a sample, and we urge that caution should be exercised when subsampling TRF distributions for telomere length analysis. Repeatability data not only validate the assay producing the data, but also may allow researchers to develop standard optimal criteria to balance cost and extent of their study design.

In the present study, quantitative data were collected to clarify the relationship between calling, call structure and eggs produced in a captive population of red drum Sciaenops ocellatus. Sciaenops ocellatus were held in four tanks equipped with long-term acoustic loggers to record underwater sound throughout a simulated reproductive season. Maximal sound production of captive S. ocellatus occurred when the photoperiod shifted from 13·0 to 12·5 h of light, and the water temperature decreased to c. 25° C. These captive settings are similar to the amount of daylight and water temperatures observed during the autumn, which is the primary spawning period for S. ocellatus. Sciaenops ocellatus exhibited daily patterns of calling with peak sound production occurring in the evenings between 0·50 h before dark and 1·08 h after dark. Spawning occurred only on evenings in which S. ocellatus were calling, and spawning was more productive when S. ocellatus produced more calls with longer durations and more pulses. This study provides ample evidence that sound production equates to spawning in captive S. ocellatus when calls are longer than 0·8 s and contain more than seven pulses. The fact that more calling, longer calls and higher sound pressure levels are associated with spawns that are more productive indicates that acoustic metrics can provide quantitative information on spawning in the wild.

A 9-week feeding trial was conducted with juvenile red drum, Sciaenops ocellatus, to evaluate the use of soy oil as a fish oil replacement. Three primary protein sources (fishmeal - FM, soybean meal - SBM, and soy protein concentrate - SPC) were utilized with 100% fish oil (FM, SBM, SPC), 75% fish oil (SBM, SPC), or 50% fish oil (FM, SBM, SPC) as the lipid source. Traditional growth and performance metrics (specific growth rate, feed consumption, feed conversion ratio) were tracked and tissue samples (liver, muscle, plasma, adipose, and brain) were collected for gas chromatography-based fatty acid profiling. Ten lipid metabolism related genes were analyzed for potential expression differences between dietary treatments in liver and muscle tissues and whole body and fillet tissues were sampled for proximate composition analyses. Forty- four fatty acids were measured by gas chromatography-flame ionization detector (GC-FID) and evaluated with principle component analysis and ANOVA to understand the dietary influence on lipid metabolism and health. Significant differences in growth rate were observed with the SBM 50% fish oil diet outperforming the FM 100% fish oil reference diet. All other soy protein-based diets performed statistically equivalent to both FM reference diets (100% and 50% fish oil) in regard to growth, however all soy protein-based formulations had significantly lower feed conversion ratios than the fishmeal-based references (p < .001). Gene expression differences were not significant in most cases, however often trended similarly as the observed performance. Fatty acid profiles differed as a function of oil source, with no apparent influence by protein source, with C18:2n-6 (linoleic acid) being-the primary differentiator. Overall, the six soy protein, fishmeal-free formulations performed equivalently or better than the fishmeal references with up to 50% of fish oil replaced by soybean oil.

Spotted Seatrout Cynoscion nebulosus are recreationally important fish that have been harvested in South Carolina for centuries. The Spotted Seatrout in South Carolina suffered substantial declines in estuarine abundance during the cold winters of 2000, 2009, and 2010, when water temperatures dropped below their tolerance threshold. As these population declines may result in genetic bottlenecks and their repetitive occurrence over a short timescale could reduce the population’s adaptive potential, we estimated the genetic diversity and effective population size (Ne) of the Charleston Harbor Spotted Seatrout population at six time points related to recent cold winters using a suite of 13 microsatellite markers. Grouping individuals by year-class (fish spawned in the same year) was the most appropriate and effective method for measuring interannual fluctuations in observed and expected heterozygosity and allelic richness, superior to partitioning fish by collection year. The genetic diversity of Spotted Seatrout was significantly influenced by catch per unit effort, although only minor changes were observed and Ne remained high. Short overlapping generations appear to allow Spotted Seatrout to genetically recover during population growth and maintain moderate levels of genetic diversity. Received May 7, 2015; accepted February 2, 2016

In this study, we investigated the metabolic effects of four different commercial soy-based protein products on red drum fish (Sciaenops ocellatus) using Nuclear Magnetic Resonance (NMR) spectroscopy-based metabolomics along with unsupervised principal component analysis (PCA) to evaluate metabolic profiles in liver, muscle and plasma tissues. Specifically, during a 12-week feeding trial, juvenile red drum maintained in an indoor recirculating aquaculture system were fed four different commercially available soy formulations, containing the same amount of crude protein, and two reference diets as performance controls: a 60 % soybean meal diet that had been used in a previous trial in our lab and a natural diet. Red drum liver, muscle, and plasma tissues were sampled at multiple time points to provide a more accurate snapshot of specific metabolic states during the grow-out. PCA score plots derived from NMR spectroscopy data sets showed significant differences between fish fed the natural diet and the soy-based diets, both in liver and muscle tissues. While red drum tolerated the inclusion of soy with good feed conversion ratios, a comparison to fish fed the natural diet revealed that the soy-fed fish in this study displayed a distinct metabolic signature characterized by increased protein and lipid catabolism, suggesting an energetic imbalance. Furthermore, among the soy-based formulations, one diet showed a more pronounced catabolic signature.

Spotted Seatrout Cynoscion nebulosus are vulnerable to mortality in winter when water temperature decreases rapidly. Temporary fishery closures in response to population declines should be based on a thorough understanding of the magnitude of winter mortality. We used three methods to estimate the low-temperature tolerance of Spotted Seatrout: the chronic lethal method (CLM) and the acclimated chronic exposure (ACE) method using both static and fluctuating temperatures. All three methods use an environmentally realistic temperature change of 1°C/d. Fish acclimated to 14°C (n = 24) for 10 d and subsequently exposed to constantly declining temperatures using the CLM experienced loss of equilibrium at a temperature of 3.57 ± 0.24°C (mean ± SD) and mortality at a temperature of 3.08 ± 0.31°C. The ACE method, which uses changing temperatures until a base temperature is reached, was used to evaluate how Spotted Seatrout are affected by prolonged, sublethal temperatures. The ACE method was performed with...

Analyses of the genetic population structure of spotted seatrout Cynoscion nebulosus along the south-eastern U.S. coast using 13 microsatellites suggest significant population differentiation between fish in North Carolina (NC) compared with South Carolina (SC) and Georgia (GA), with New River, NC, serving as an area of integration between northern and southern C. nebulosus. Although there is a significant break in gene flow between these areas, the overall pattern throughout the sampling range represents a gradient in genetic diversification with the degree of geographic separation. Latitudinal distance and estuarine density appear to be main drivers in the genetic differentiation of C. nebulosus along the south-eastern U.S. coast. The isolation-by-distance gene-flow pattern creates fine-scale differences in the genetic composition of proximal estuaries and dictates that stocking must be confined to within 100 km of the location of broodstock collection in order to maintain the natural gradient of genetic variation along the south-eastern U.S. coast.

Understanding the genetic relationships of Striped Bass Morone saxatilis populations within and between watersheds is necessary to identify appropriate management units. Determining temporal changes in genetic relationships as well as the genetic diversity of the populations is important in understanding how stock enhancement influences population units. A suite of 12 microsatellites was used to evaluate patterns of Striped Bass gene flow both spatially and temporally across watersheds in the southeastern United States. Populations from the study watersheds were genetically diverse with the exception of the Savannah River, South Carolina–Georgia, which is recovering from a major population decline. Striped Bass in the Roanoke and Cape Fear rivers, North Carolina, represented a single population, most likely due to historical transfer stocking across the state from Roanoke River stock. Watersheds in South Carolina contained genetically distinct Striped Bass populations, although the difference betw...

Cobia (Rachycentron canadum) is a pelagic, migratory species with a transoceanic distribution in tropical and subtropical waters. Recreational fishing pressure on Cobia in the United States has increased substantially during the last decade, especially in areas of its annual inshore aggregations, making this species potentially susceptible to overfishing. Although Cobia along the Atlantic and Gulf coasts of the southeastern United States are currently managed as a single fishery, the genetic composition of Cobias in these areas is unclear. On the basis of a robust microsatellite data set from collections along the U.S. Atlantic coast (2008–09), offshore groups were genetically homogenous. However, the 2 sampled inshore aggregations (South Carolina and Virginia) were genetically distinct from each other, as well as from the offshore group. The recapture of stocked fish within their release estuary 2 years after release indicates that some degree of estuarine fidelity occurs within these inshore aggregations and supports the detection of their unique genetic structure at the population level. These results complement the observed high site fidelity of Cobias in South Carolina and support a recent study that confirms that Cobia spawn in the inshore aggregations. Our increased understanding of Cobia life history will be beneficial for determining the appropriate scale of fishery management for Cobia.

Genetic population structure of anadromous striped bass along the US Atlantic coast was analyzed using 14 neutral nuclear DNA microsatellites. Young-of-the-year and adult striped bass (n = 1114) were sampled from Hudson River, Delaware River, Chesapeake Bay, North Carolina, and South Carolina. Analyses indicated clear population structure with significant genetic differentiation between all regions. Global multilocus FST was estimated at 0.028 (P < 0.001). Population structure followed an isolation-by-distance model and temporal sampling indicated a stable population structure more than 2 years at all locations. Significant structure was absent within Hudson River, whereas weak but significant genetic differences were observed between northern and southern samples in Chesapeake Bay. The largest and smallest effective striped bass population sizes were found in Chesapeake Bay and South Carolina, respectively. Coalescence analysis indicated that the highest historical gene flow has been between Chesapeake Bay and Hudson River populations, and that exchange has not been unidirectional. Bayesian analysis of contemporary migration indicated that Chesapeake Bay serves as a major source of migrants for Atlantic coastal regions from Albemarle Sound northward. In addition to examining population genetic structure, the data acquired during this project were capable of serving as a baseline for assigning fish with unknown origin to source region.

Background Fish sound production is widespread throughout many families. Territorial displays and courtship are the most common reasons for fish sound production. Yet, there is still some questions on how acoustic signaling and reproduction are correlated in many sound-producing species. In the present study, our aim was to determine if a quantitative relationship exists between calling and egg deposition in captive spotted seatrout (Cynoscion nebulosus). This type of data is essential if passive acoustics is to be used to identify spawning aggregations over large spatial scales and monitor reproductive activity over annual and decadal timeframes. Methods Acoustic recorders (i.e., DSG-Oceans) were placed in three laboratory tanks to record underwater sound over an entire, simulated reproductive season. We enumerated the number of calls, calculated the received sound pressure level, and counted the number of eggs every morning in each tank. Results Spotted seatrout produced three distinct call types characterized as “drums,” “grunts,” and “staccatos.” Spotted seatrout calling increased as the light cycle shifted from 13.5 to 14.5 h of light, and the temperature increased to 27.7 °C. Calling decreased once the temperature fell below 27.7 °C, and the light cycle shifted to 12 h of light. These temperature and light patterns followed the natural reproductive season observed in wild spotted seatrout in the Southeast United States. Spotted seatrout exhibited daily rhythms in calling. Acoustic signaling began once the lights turned off, and calling reached maximum activity approximately 3 h later. Eggs were released only on evenings in which spotted seatrout were calling. In all tanks, spotted seatrout were more likely to spawn when male fish called more frequently. A positive relationship between SPL and the number of eggs collected was found in Tanks 1 and 3. Discussion Our findings indicate that acoustic metrics can predict spawning potential. These findings are important because plankton tows may not accurately reflect spawning locations since egg capture is likely affected by predator activity and water currents. Instead, passive acoustics could be used to monitor spotted seatrout reproduction. Future studies can use this captive study as a model to record the estuarine soundscape precisely over long time periods to better understand how human-made stressors (e.g., climate change, noise pollution, and chemical pollutants) may affect spawning patterns.

The South Carolina Department of Natural Resources has been stocking red drum Sciaenops ocellatus since 1988 to evaluate parameters critical to their successful survival and recruitment in South Carolina estuaries. From 1999 to 2002, between 600,000 and 1,000,000 juvenile red drum were stocked each year in two tributaries of Charleston Harbor. The harbor and each tributary were partitioned into three independent strata and randomly sampled monthly for two decades, allowing population trends before, during, and after stocking to be evaluated. Using microsatellite-based parentage analysis, we examined the contribution of stocked age-0 juvenile red drum (15–60 mm total length) to the local population 1 year after release by using fishery-independent sampling. Analysis of these data showed that the highest contributions (88.9%) were close to the stocking site in years with low natural recruitment, whereas in years with high natural recruitment, contributions were lower and stocking was less effective...

Across a species' range, the population dynamics of some areas may express spatial syn- chrony (i.e. they fluctuate with one another), whereas other areas may express no synchrony (they fluctuate independently). The degree of synchrony and spatial extent of synchrony are important considerations when assessing the population as a whole. We examined these aspects in red drum Sciaenops ocellatus along the coast of South Carolina using long-term survey data of juvenile abun- dance in estuarine areas separated by up to ~200 km. Synchrony of year class strength was detected among areas, but the degree of synchrony declined significantly with distance. By comparison, genetic segregation along the coast was either weak or undetectable (based on allele frequencies at 8 microsatellite loci), although it depended on the year class (2004, 2005 or 2007) of fish that was tested. By standardizing juvenile abundance data across estuaries and survey types, a single, region- wide juvenile time series was generated that covered the 1985-2007 year classes. The juvenile time series correlated significantly with the year class composition of the present-day adult population, which was determined using otoliths collected by a separate survey operating in deeper adult habi- tats. Future work integrating data across even broader spatial scales would assist in the understand- ing of large-scale ecological processes that control fluctuations in red drum populations, and would provide useful information for fishery managers.

Microsatellite multiplexing is a useful technique that minimizes the time, reagents, and cost associated with genetic studies in fisheries biology. Striped Bass is an important sport and aquaculture species commonly stocked throughout the United States. We have developed three multiplexed panels that collectively incorporate twelve different established microsatellite loci. All loci were tested for Hardy-Weinberg equilibrium, linkage disequilibrium, Mendelian inheritance, and null alleles in two populations. Loci were comparably polymorphic in two river systems with similar allele size ranges observed; therefore, these multiplexed panels should be useful for genetic population studies of Striped Bass both within and between disparate geographic distributions.

Lipid content, lipid class and fatty acid compositions were determined in eggs from wild and captive black sea bass, Centropristis striata L., from northern (New England) and southern (South Carolina) regions to determine the effects of diet on egg composition and fertilization success. The formulated diets fed to the northern captive (NC) fish were higher in total lipids (22%) compared with the cut fish and squid diet fed to the southern fish (SC; 3.3% lipid) and had a higher relative amount of linoleic acid (LA) and lower relative amounts of docosahexaenoic acid (DHA) and arachidonic acid (AA). These dietary differences were broadly reflected in the egg lipid composition. The LA levels were higher in all lipid classes in eggs of NC fish while AA levels were lower. The DHA was higher in the major polar lipids (PL) (phosphatidylcholine and phosphatidylethanolamine) of SC eggs compared with NC. Compared with wild fish, both captive groups produced eggs with PLs richer in LA and lower in DHA and AA. Over all fish groups, fertilization success was directly correlated with levels of DHA and AA in the PLs and was inversely correlated with LA levels.

The red drum Sciaenops ocellatus is an estuarine-dependent fish that is the focus of a large recreational fishery along the U.S. Atlantic coast and in the Gulf of Mexico. In response to dramatic declines in juvenile abundance, the South Carolina Department of Natural Resources has been experimentally stocking local estuaries since the late 1980s. Here we report on the genetic parentage approach that has been employed to identify fish of hatchery origin through DNA isolated from fin clips collected from wild-caught fish. In some cases tissue samples were not available, making it necessary to find an alternative source of DNA. Thus, we also examined the use of archived otoliths as a source of genetic material for parentage analysis. Amplification resulted from 96% of the extractions obtained from the extracellular tissue remaining on otoliths. In comparison with extractions obtained from fin clips, otoliths appear to be a reliable DNA source. These results not only present a method for nonlethally ...

The objectives of this research were to optimize techniques for the mass marking of larval red drum Sciaenops ocellatus with oxytetracycline (OTC) by testing effects of salinity (i.e., total dissolved solids [TDS], either as artificial sea salt [AS] or laboratory-grade NaCl) and immersion duration on fish survival and mark retention. Survival of larvae immersed for 24 h was greater than 83% for all combinations of salinity (15–30 g of TDS/L of water) and OTC concentration (0–500 mg of OTC/L of water). Treatments with the lowest Ca2+ and Mg2+ concentrations ([Ca2+] and [Mg2+]; i.e., highest NaCl in substitution of AS), highest OTC concentrations, and longest exposure times yielded the poorest survival (mean ± SD = 63.3 ± 5.8%). Conversely, mark quality (on a scale of 1–5, where 1 = best and 5 = worst) was greatest (1.4 ± 0.4) in treatments with the lowest [Ca2+] and [Mg2+]. Larval survival (>93%) and mark quality (2.3 ± 0.1) were acceptable under a combination of 500-mg/L OTC, 30-g/L TDS (80% of n...

Mature black sea bass, Centropristis striata L. (200–800 g), were captured in coastal South Carolina during the spawning season and administered hormones for ovulation induction and strip spawning. During both study years, control groups of females were incorporated into the study design and administered sham injections containing physiological saline solution. In 2004, females received a single intramuscular injection of human chorionic gonadotropin (hCG) (330 IU kg−1) (n=8) or two injections of hCG at 24-h intervals (n=8). In 2005, females received a single injection of hCG (n=10) or an analogue of luteinizing hormone releasing hormone (LHRHa) (n=10). In 2004, all fish administered a single dose of hCG ovulated at least once. Six fish ovulated on two consecutive days and one fish ovulated on 3 days consecutively. In contrast, six of eight fish receiving two doses of hCG ovulated once, five ovulated on 2 days successively and three fish ovulated 3 days in succession. Of the fish that spawned, no differences were found in any reproductive parameters. In 2005, all fish administered hCG or LHRHa ovulated at least once. Three fish administered hCG ovulated twice, four fish ovulated on three consecutive days and one fish 4 days successively. All fish administered LHRHa spawned at least twice, six fish ovulated thrice and three fish ovulated 4 days, successively. A significant difference in fertility was found between hCG (75.6±11.4%) and LHRHa (55.6±27.4%). The results of this study indicate that both hCG and LHRHa are effective for ovulation induction in prespawning black sea bass.

The effects of culture parameters of tank color and feeding regimes were examined on larval white bass Morone chrysops during 1994–1995. Under high surface illumination (998 lux), dark tank walls were essential for effective prey capture. Larvae reared in clear glass aquaria did not grow and had died by day 6 of the study. In contrast, 48.7% of the larvae reared in black-walled tanks were alive on day 24 and had grown to 17.2 mm total length (TL). In another study, larvae were fed rotifers Brachionus plicatilis and Artemia nauplii in different feeding protocols. In one treatment only rotifers (10/mL) were fed day 1 (4 d post-hatch), rotifers and Artemia (3/mL) were fed days 2–4, and Artemia fed days 5–15. This protocol produced similar growth (mean size 11.7 mm TL) and survival (mean 30.3%) as slower weaning times from rotifers to Artemia. Juveniles (27-day-old, 17.2 mm TL) were converted to a dry crumble diet over a 14-d period by slow transfer from a combination diet consisting of live Artemia nauplii, frozen adult Artemia, plankton flakes and dry crumbles. Survival offish weaned to the dry diet was 64.5%. Most of the mortalities during the weaning period were fish with uninflated swim bladders which were cannibalized by larger fish. Using the above tank culture techniques, white bass were reared to a mean size of 73.2 mm TL (mean weight 5.8 g) over a 73-d period. This essentially closes the life cycle of white bass.

Research was conducted at the South Carolina Department of Natural Resources Waddell Mariculture Center to evaluate the potential for captive reproduction of cobia, Rachycentron canadumin outdoor tanks and ponds. In May 2001, adult cobia (3 males, 1 female, and 1 suspected female) obtained from a local high salinity estuary were stocked into an outdoor tank (32,000-L) receiving ambient estuary water. Spawning occurred within 2 days after stocking. Over the course of 3 consecutive days, a total of 3.6 million eggs were collected with roughly equal numbers collected during each 24-hour period. Mean fertilization rate was 58.1%. Hatching occurred at approximately 24 hours after initiation of each spawning event. Mean percent hatch was 27.5%. Fish were relocated to a 0.25-ha circular pond 10 days after tank spawning activity ended. One female received pelleted GnRHa before stocking. Eggs were observed 3 days after stocking and at 12 days after hatching, approximately 50,000 larvae were harvested. In ...

The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ∼9 WPS, after which pond water temperatures ...

Red drum Sciaenops ocellatus have been classified by the Atlantic States Marine Fisheries Commission as overfished in the Atlantic off the southeastern USA. A study was conducted to evaluate stocking hatchery-reared fish as a management tool to increase abundance of red drum in South Carolina estuaries. Multiple groups of juveniles, at mean sizes of 22–56 mm total length, were released after being marked by immersion in 15 g/L salinity brackish water containing oxytetracycline HCl (500 mg/L active). Fish were released into a small (535-ha) part of the available nursery habitat (total = 25,000 ha) in the Port Royal Sound estuary each fall and spring from fall 1995 through spring 1997. During fall 1995 and spring 1996, 347,000 fish were stocked; during fall 1996 and spring 1997, the number was 1,228,000. Movement of hatchery fish from the release site was monitored for at least 2 years after release. Overall, hatchery fish accounted for 19.0% of the 627 fish (age 0 to age 2) captured from the 1995 ...

Cobia Rachycentron canadum juveniles (119.7 mm TL, weight 8.5 g) were reared for 10 wk at three salinity levels: 5 ppt, 15 ppt. and 30 ppt. Growth and survival were determined through biweekly sampling. Blood samples obtained at termination of the study were analyzed to determine hematocrit, blood osmolality, and total protein. Results indicated that the overall growth of fish was significantly affected by salinity. Mean (± SE) total length (TL) and weight of fish reared at a salinity of 30 ppt were 201.7 ± 2.6 mm and 47.6 ± 1.9 g, respectively, followed by fish reared at 15 ppt (182.2 ± 1.7 mm, 34.1 ± 1.6 g). and 5 ppt (168.3 ± 5.8 mm TL, 28.3 ± 2.3 g). Differences in specific growth rates among treatments for the 10-wk period were also significant. No differences were detected in mean survival among fish reared at salinities of 5, 15, and 30 ppt (84, 94, and 94%, respectively). However, fish reared at salinity 5 ppt appeared to be in poor health as skin lesions, fin erosion, and discoloration were evident. Analysis of blood revealed that, while no differences existed among treatments with respect to plasma total protein, fish reared at a salinity of 5 ppt exhibited significantly reduced hematocrit (25% vs. > 30%) and plasma osmolality values (318 vs. > 353 mmolkg) relative to fish reared at higher salinities. Cobia can tolerate exposure to low salinity environments for short periods of time without mortality; however, moderate to high salinities are required for sustained growth and health of this species.

The black sea bass is a high-value marine serranid and is a prime candidate for intensive cultivation. Reliable methods for controlled spawning are needed to accelerate the development of hatchery technologies that result in mass production of healthy juveniles. During 1998–2001, spawning studies were conducted at The University of North Carolina at Wilmington (UNCW) and at the South Carolina Department of Natural Resources (SCDNR), Charleston, using pelleted luteinizing hormone releasing hormone analogue (LHRH-a). From April through July 2001, 28 vitellogenic-stage females, with mean oocyte diameters (MOD) ranging from 277–448 μm, were implanted with a 95% cholesterol-5% cellulose pellet containing LHRH-a (-50 μg/kg body wt) at UNCW. In 10 individual spawning trials, females with MOD of 305–448 μm and maximum oocyte diameter × 475 μm spawned volitionally beginning 2–3 d post-implantation (PI) and continued spawning over an average of 1.9 d (range = 1–4 d). Individual females released a mean total of 149,000 eggs (117,000 eggs/kg) with a mean buoyancy rate of 40.5% (floaters). Fertilization and hatching rates were 98% and 27.2% of floaters, respectively, yielding 14,600 yolksac larvae/female (12,600 yolksac larvae/kg body wt), and overall egg viability averaged 8.9%. In eight group spawning trials (2–3 females/group), average performance of females, including fecundity (103,800 eggs/female; 105,500 eggs/kg body wt), buoyancy rate (42.5%), fertilization and hatching rates (97.7% and 24.3% of floaters), numbers of yolksac larvae produced (10,900 yolksac larvae/female; 10,100 yolksac larvae/kg body wt), and overall egg viability (10.6%) was comparable to what was seen in individual spawning trials. From 1998–2000, a total of 58 vitellogenic stage (70% of oocytes 500 pm) females were implanted with pelleted LHRH-a (-50 μg/kg body wt) in nine group spawning trials (2–19 females/group) at SCDNR. Volitional spawning typically began 18–42 h PI and recurred every 1–3 d for an average duration of 9 d. Female groups released a mean of 560,000 eggs (84,000/female; 132,000/kg body wt) over the spawning period, with mean buoyancy rate of 25.7% floaters. Fertilization and hatching rates were 17.7% and 11.6 % of floaters, respectively, yielding 4,300 yolksac larvae/female (4,600 yolksac larvae/kg body wt). Overall egg viability was 2.9%. Captive wild-caught black sea bass were induced to undergo repetitive volitional spawning by implantation of pelleted-LHRH-a, consistent with a multiple clutch group synchronous pattern of ovarian development. Group spawning appears to be a practical way to compensate for variable fecundity and egg viability of individual females. Research is needed to identify optimum hormone treatments and eligibility requirements.

In a pilot-scale stocking program, juvenile red drum Sciaenops ocellatus were immersed for 4 h in a 500-mg/L active solution of oxytetracycline hydrochloride (OTC) and 15-g/L salinity water at a temperature of 26.2°C to mark the otoliths before release. A portion of the treated fish was retained to determine marking success and mark retention. Retained fish were held in outdoor tanks supplied with flow-through estuarine water from Charleston Harbor, South Carolina, and fed commercial trout diets daily. During a 4.4-year period, subsamples of treated fish were regularly sacrificed, and their sagittae were removed, sectioned, and examined under an epifluorescent microscope to validate presence of a mark. Because of interference from autofluorescence, OTC marks were not detectable on sagittae from fish sampled 56 d after immersion (N = 4). However, a mark was visible on 100% of sagittae examined from treated fish sampled on nine occasions from 73 to 1,618 d after immersion (N = 46). In a blind test,...

An experimental stock enhancement program was conducted in Port Royal Sound estuary, South Carolina, in which cultured juvenile red drum (Sciaenops ocellatus, 2–3 cm TL, ∼40 days old) were released into a system of shallow tidal creeks that flow into the Colleton River. All fish were immersed in oxytetracycline (OTC) prior to release to produce an identifiable, chemical mark on the otoliths. The release area was typical of primary nursery habitat in this region. For four years post-stocking, fish were collected throughout the sound using hook and line, spear, and trammel net. Otoliths were examined for OTC marks to determine which fish were of hatchery origin. It was found that while dispersal was substantial, many stocked fish stayed in the general area of release (1.8 × 3.2 km) until reaching the age of maturity (∼age 3) when they left the estuary, and at all ages they were mixed with wild fish. This suggests that relatively small areas containing the appropriate suite of habitat types could be...

Angler reporting of tagged red drum ( Sciaenops ocellatus ) was examined using three tag reward messages: “No Reward”; “Reward”; and “$50 Reward”. “Reward” is the standard message used in all state sponsored fin fish tagging programs in South Carolina (SC). Hatchery produced red drum were tagged with external tags containing the various messages and released in four replicate areas ( n = 100 fish/message/area) near Port Royal Sound. Analysis of the return data for “Reward” (18.7%) and “$50 Reward” (22.9%) tags found no statistical differences ( P > 0.05) between the two groups. However, significantly ( P

— In South Carolina, studies have been conducted to develop rearing techniques for southern flounder Paralichthys lethostigma a candidate for aquaculture development and stock enhancement programs. To help define environmental tolerances, a variety of salinity studies were conducted with the early life stages of this species. Eggs were buoyant at 32 ppt and sank at 29 ppt with salinities of 30–31 ppt providing varying levels of suspension in the water column. Eggs incubated at 0 and 5 ppt all died, whereas 82.5% hatched at 10 ppt but larvae died shortly thereafter. At 63 h post-fertilization, there were no differences in hatch level for eggs incubated at salinities of 15 to 35 ppt (mean hatch level 98.5%). In a 72-h study, fish 3 wk post-metamorphosis (13.7 mm TL, 50-d-old) were acclimated to seven salinities ranging from 0–30 ppt. Fish held at 0 ppt salinity exhibited a statistically (P < 0.05) lower survival (20.0%) than those exposed to 5–30 ppt salinity concentrations. No differences were detected in survival (mean 99.1%) among fish held in the higher salinities. A second study examined the tolerance of older juveniles to lower salinities. Juvenile flounder (95.2 mm TL, 220-d-old) were acclimated to 0, 1,5 and 10 ppt salinities and reared for 2 wk. Results showed that fish could tolerate salinities of 0–10 ppt (100% survival). These data indicate that salinity tolerance of southern flounder increases with age. In addition to the short duration studies, a replicated 11-mo duration tank grow-out study was conducted at mean salinity 5.4 ppt and mean temperahue 22.6 C with an all male population. Flounder grew from a mean length of 100 mm to 213 mm TL and weight from 8.9 to 104.3 g. Growth of the cultured fish approximated that observed among male flounders in the wild.

An otolith-based method that permits rapid and accurate differentiation between hatchery-produced and wild red drum Sciaenops ocellatus was identified. Sagittae from several year-classes of hatchery-produced (both stocked and captive) and wild red drum more than 18 months old were examined. Hatchery fish were spawned in spring, about 6 months before the natural spawning season. On sagittae, the distance from the core to the first annulus (mean = 1,247 μm) for three year-classes of wild fish collected before hatchery releases was significantly larger (P < 0.001) than that for three year-classes of hatchery fish (mean = 690 μm). Although there were differences in core–annulus distance among year-classes of hatchery fish, neither the 99% confidence intervals nor the core–annulus distance ranges overlapped for hatchery and wild fish. Springs-pawned red drum deposited an annulus during the first winter, whereas wild fish deposited an annulus during the second winter, at an age of approximately 18 mont...

In 1995, two studies were conducted at the Marine Resources Research Institute, Charleston, South Carolina, that focused on development of techniques to intensively rear larval sunshine bass, the hybrid of female white bass Morone chrysops and male striped bass M. saxatilis. During the first study, the rotifer Brachionus plicatilis was shown to be an acceptable first-food when fed at 10 organisms/mL in static black tanks receiving high surface illumination (mean, 600 lx). It was further demonstrated that larvae could be switched to a diet of just nauplii of Artemia sp. by at least day 8 post-hatch. At the conclusion of the 8-d study, larvae fed Artemia nauplii earlier were significantly larger (9.12 mm total length, TL) than larvae fed rotifers through day 7 posthatch (6.71 mm TL). However, there were no survival differences (mean, 67.2%). During the second study, supplementation of the Artemia nauplii diet with a commercial larval feed offered no advantage to 12-d-old larvae, which had similar s...