Juvenile and adult black sea bass (Centropristis striata L.) were exposed to various concentrations of four anaesthetics to determine practical dosages for handling as well as for procedures such as bleeding, ovarian biopsy or tag implantation. In experiment 1, juveniles exposed to either 2.0 mg L À 1 metomidate, 15 mg L À1 clove oil, 70 mg L À1 tricaine methanesulphonate (TMS) or 200 mg L À 1 2-phenoxyethanol (2-PE) reached stage II of anaesthesia in 3^5 min and could be handled for weighing and measuring. All ¢sh had completed recovery to stage III within 6 min. In experiment 2, the established concentrations of each anaesthetic were tested on juveniles to determine their ability to prevent a re£ex to a subcutaneous needle puncture. All of the ¢sh exposed to clove oil (20 mg L À 1 ) and 40% of the TMS-treated (70 mg L À 1 ) ¢sh reacted while none of the ¢sh anaesthetized in metomidate (2.0 mg L À1 ) or 2-PE (200 mg L À 1 ) responded to the needle puncture. In experiment 3, metomidate (5.0 mg L À1 ), clove oil (30 mg L À1 ) TMS (125 mg L À1 ) or 2-PE (300 mg L À 1 ) were all e¡ective for performing an ovarian biopsy or tag implantation on adults. In experiment 4, TMS (125 mg L À1 ) exacerbated the cortisol response to a short handling stressor during a 30 min exposure. Fish anaesthetized in 2-PE (300 mg L À 1 ), metomidate (5.0 mg L À 1 ) or clove oil (40 mg L À 1 ) had increased cortisol levels associated with the handling stressor but there were no further increases during the re-mainder of the experimental period. The results demonstrate that these anaesthetics are e¡ective for sedation and anaesthesia of black sea bass and that the best choice is dependant upon the procedures to be performed.

Atlantic cod Gadus morhua in US waters are currently managed as 2 stocks: (1) a Gulf of Maine stock and (2) a Georges Bank and south stock. This designation is decades old and warrants re-evaluation in light of concerns that fisheries management units may not reflect biologically meaningful population units. In this study, we used 10 microsatellite loci, the PanI locus, and 5 single nucleotide polymorphism markers to characterize the population genetic structure of cod in US waters. We found significant differentiation among temporally and spatially divergent populations of cod (global F ST = 0.0044), primarily stemming from 2 potentially non-neutral loci, and evidence for a population structure that strongly contradicts the current 2-stock management model. This genetic structure was stable over a 5 yr period. Our results indicate that cod in US waters are broadly structured into 3 groups: (1) a northern spring-spawning coastal complex in the Gulf of Maine (GOM), (2) a southern complex consisting of winter-spawning inshore GOM, offshore GOM and sites south of Cape Cod, Massachusetts, and (3) a Georges Bank population. The strongest differentiation occurs between populations in the northern and southern complex (mean F ST = 0.0085), some of which spawn in the same bays in different seasons. By means of mixture analysis, young-of-the-year fish sampled on juvenile nurseries were assigned to the spawning complex of their origin. Our findings contribute to a growing body of knowledge that Atlantic cod and other marine fish populations are structured on a finer scale than previously thought and that this structure supports biocomplexity and locally adapted populations. As such, it may be warranted to re-evaluate current management units and tailor management plans toward this finer scale.KEY WORDS: Atlantic cod · Microsatellite DNA · Single nucleotide polymorphism · Population genetic structure · Stock identification · Gadus morhua Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 410: [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194][195] 2010 the importance of processes that limit dispersal and promote self-replenishment of local populations, such as sedentary adult life history strategies (Robichaud & Rose 2004, Howell et al. 2008, spawning site fidelity (Taggart 1997), natal homing (Thorrold et al. 2001, Svedäng et al. 2007), egg and larval retention (Jones et al. 1999, 2005, Bradbury et al. 2008) and local adaptation (McIntyre & Hutchings 2003, Conover et al. 2006, Hutchings et al. 2007). The implications of such fine-scale population structure are important for effective management (Palumbi 2003, Bradbury et al. 2008, Reiss et al. 2009).One marine fish species known to exhibit fine-scale population structure in parts of its distribution is Atlantic cod Gadus morhua L. (see reviews in Waldman 2005 andCarvalho 2008). Atlantic cod is one of the most commercially important marine fishes in the world and comprises a p...

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Wild striped bass,Morone saxatilis, were collected from coastal waters and spawning areas to describe the endocrine correlates of oocyte development in non-captive, migratory fish. The fish were classified according to their most advanced oocytes. Serum levels of estradiol (E2), testosterone (T) and 17α-20β-dihydroxyprogesterone (DHP) were measured by radioimmunoassay (RIA). Females in the primary growth phase and early secondary growth phase (pre-vitellogenic) had low levels of plasma steroids, ovarian lipid content and gonadosomatic indices (GSIs). Significant increases in E2, T, ovarian lipid content and GSIs occurred during the vitellogenic phase. Maximum levels of all reproductive parameters were found in prespawning fish sampled in the Hudson River. Mean levels of E2, T, ovarian lipids and GSIs for these fish were 2.0±0.5 ng/ml, 3.0±0.3 ng/ml, 24±1 mg/g, and 5.6±0.3% (mean±SEM), respectively. In fish induced to spawn with human chorionic gonadotropin (HCG), DHP levels (1.9±0.4 ng/ml) were significantly elevated. Similar levels were found in two fish captured during the spawning season, suggesting that DHP may serve as the maturation-inducing steroid in 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.

Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different (P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect (P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower (P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different (P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two‐step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.

Management of Atlantic cod Gadus morhua in U.S. waters is based on a two‐stock model composed of stocks from (1) the Gulf of Maine (GOM) and (2) Georges Bank (GB) and areas south; however, evidence suggests a more fine‐scale structuring. We used microsatellite and single nucleotide polymorphism (SNP) analyses to investigate the stock structure of Atlantic cod in U.S. waters. In year 1, we analyzed microsatellite loci in larvae from GB, age‐0 juveniles from multiple locations in the GOM, and adults of unknown maturity from GB, Jeffreys Ledge, and the Great South Channel (GSC). In year 2, Atlantic cod collected from spawning aggregations in Ipswich Bay in the spring and at GB, Stellwagen Bank, Chatham, and Ipswich Bay in the winter, along with adults of unknown maturity from Long Island, New York, were surveyed at a modified battery of microsatellites and three SNPs. In year 1, we saw no significant differences in allelic frequencies between our composite sample of adult and juvenile cod from the GOM and that from GB nor between the collections from the GSC and any other site. However, a composite sample of juveniles from Massachusetts Bay was significantly different from the GB collection and juveniles from Maine. In year 2, we found highly significant differences in allelic frequencies between Atlantic cod collections from the GOM and GB. The spring collection from Ipswich Bay was highly distinct from the collection from GB and all other sites, including the winter‐spawning Ipswich Bay collection. The Long Island sample was genetically distinct from the GB and the spring collections from Ipswich Bay, but not from other collections. Our study indicates that there is genetic heterogeneity of stocks in U.S. waters, but its structure is complex and to better understand it many more spatially and temporally separated samples must be characterized.

Four experiments were conducted to investigate the effects of feeding frequency on growth of juvenile Atlantic halibut, Hippoglossus hippoglossus L. Fish (22–75 g) fed three (3 ×) or five times per day (5 × day−1) under constant light and temperature (13±1°C) consumed significantly more feed than fish fed 1 × day−1 but by the end of the experiment only fish fed 5 × day−1 were heavier and had greater specific growth rates (SGR). Under simulated winter conditions (9L:15D, 5±1°C), halibut (∼300 g) fed every other day consumed more feed, had a greater SGR and final weight compared with fish fed every third day. Feed conversion ratios were not different among treatment groups in any of the experiments. These results suggest that growth rates may be improved by feeding juvenile halibut more than 1 × day−1.