David L. Berlinsky

Stock Identification of Atlantic Cod in U.S. Waters Using Microsatellite and Single Nucleotide Polymorphism DNA Analyses

Abstract 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 G...

Effects of Partial Replacement of Fish Meal Protein by Microalgae on Growth, Feed Intake, and Body Composition of Atlantic Cod

Abstract A feeding trial was conducted with juvenile Atlantic cod Gadus morhua (initial mean weight, 40.7 g) in which a combination of dried Nannochloropsis sp. and Isochrysis sp. replaced fish meal protein in isonitrogenous, isocaloric diets. Three experimental diets (55% protein, 16.5% fat; calculated gross energy = 5,328 kcal/kg) were formulated to replace 0, 15, or 30% of dietary fish meal protein. At the conclusion of the 84-d study, no differences in survival, feed conversion ratios, viscerosomatic indices, and n-3 and n-6 fatty acids in the muscle were found among the treatment groups. Feed intake and growth, which were proportional to the level of algal incorporation, were significantly reduced in the algae-fed fish and were probably due to palatability problems. Feed intake improved in the fish fed the diet with 15% fish meal protein replacement as the study progressed, but hepatosomatic indices indicate that those fed the diet with 30% replacement were approaching starvation. Received July 13, 2...

Partial Replacement of Fish Meal with Laver Porphyra spp. in Diets for Atlantic Cod

Abstract Juvenile Atlantic cod Gadus morhua (initial mean weight = 15.6 g) were fed three isonitrogenous, isocaloric diets (55% protein, 16% fat; calculated gross energy ≈ 20.5 MJ/kg) containing dried laver (nori) Porphyra spp. (red algae) to replace 0, 15, and 30% of the fish meal in a commercially available marine finfish diet. After 84 d, no differences in survival, growth, or hepatosomatic index were found among the treatment groups. The fish attained an average weight of 41.0 g, a specific growth rate (SGR) of 1.19%, and a feed conversion ratio (FCR) of 1.26. The fatty acid composition of the muscle was similar among treatment groups except that arachidonic acid levels were greater in fish given diets with 30% Porphyra replacement. These results indicate that Porphyra spp. at levels up to 30% provide a suitable fish meal replacement in diets for juvenile Atlantic cod.

Partial Replacement of Fish Meal with Soy Protein Concentrate in Diets of Atlantic Cod

Abstract In two feeding trials conducted with juvenile Atlantic cod Gadus morhua (initial mean weight = 87.9 or 15.92 g), soy protein concentrate (SPC) was used to replace fish meal in isonitrogenous, isocaloric diets. In the first trial, five experimental diets (47% protein, 15% fat; calculated gross energy = 5,059 kcal/kg) were formulated to replace 28, 60, 80, and 100% of dietary fish meal. In the second trial, three diets were formulated with SPC to replace 0, 25, and 50% of the fish meal in a modified commercial diet for marine finfish (50% protein, 15% fat; calculated gross energy = 4,900 kcal/kg; calculated digestible energy = 3,570 kcal/kg). Upon conclusion of the studies, no differences in survival, growth, hepatosomatic index, or viscerosomatic index were found among the treatment groups. The fish attained mean weights of 162.7 and 39.1 g in the first and second trials, respectively, with specific growth rates of 0.76% and 1.12% and feed conversion ratios of 1.28 and 1.29, respectively. No consi...

Development of Practical Culture Methods for Rainbow Smelt Larvae

Abstract Rainbow smelt Osmerus mordax, collected in the wild and strip-spawned during the 2002 and 2003 spawning seasons, produced fertilization and hatching rates as high as 99% and 86%, respectively. During the 2002 spawning season, embryos were stocked into petri dishes and the effects of temperature (5, 10, 15, and 20°C) and salinity (0, 10, 20, and 30‰) on hatching success were determined. Hatching was significantly greater at 10°C and 15°C than at 5°C and 20°C, regardless of salinity. No hatching occurred at 20‰ or 30‰ salinity at any temperature. In separate experiments, the effects of light intensity, green water (200,000 microalgal cells/mL), temperature, and salinity on larval growth and survival were tested. Growth and survival were significantly improved by the addition of green water, but no significant differences were found between light intensity treatments. In studies conducted during the 2003 spawning season, there was no difference in survival between rainbow smelt larvae reared at 15°C...

Identification of ovarian gene expression patterns during vitellogenesis in Atlantic cod (Gadus morhua).

Follicular maturational competence and ovulatory competence in teleost fish refer to the ability of the ovarian follicle to undergo final oocyte maturation and ovulation, respectively, in response to gonadotropin stimulation and other external cues. Some gene products related to competence acquisition are likely synthesized during vitellogenic growth, as these follicles gain in vivo responsiveness to exogenous gonadotropin stimulation and can be induced to undergo maturation and ovulation. In Atlantic cod (Gadus morhua), gonadotropin responsiveness has been shown to be oocyte size-dependent, and only ovaries containing late-stage vitellogenic follicles can be induced to ovulate. The purpose of the present study was to compare gene expression patterns between mid (unresponsive) and late (responsive) vitellogenic ovaries to identify genes involved in gonadotropin responsiveness and the acquisition of maturational and ovulatory competencies. Representational difference analysis was conducted in two reciprocal comparisons using intact ovarian fragments and follicle wall-enriched tissues, and genes of interest were used in real time quantitative PCR to confirm differential expression. Few differences were detected in intact ovarian fragments, but type IV ice-structuring protein and gephyrin were upregulated later in development and may be involved in lipid and sulfur metabolism, respectively. Candidate gene assays for luteinizing hormone receptor and aromatase also exhibited significant upregulation during vitellogenesis. Many genes were differentially expressed in follicle wall-enriched tissues, including endocrine maturational regulators and smooth muscle genes. Overall, maturational and ovulatory competencies during vitellogenesis in Atlantic cod are associated with up- and downregulation of many genes involved in lipid metabolism, endocrine regulation, and ovulatory preparation.

Surface Disinfection and Removal of Adhesiveness from Rainbow Smelt Eggs

Abstract The survival of rainbow smelt Osmerus mordax embryos was evaluated after treating fertilized eggs with tannic acid (150, 300, 600, or 1,200 mg/L) in suspension for 10 min to remove adhesiveness or treating them with calcium hypochlorite (25, 50, 75, or 100 mg/L), polyvinylpyrrolidone iodine (PVP-I; 25, 50, 75, or 100 mg/L), or hydrogen peroxide (H2O2; 500, 1,000, 1,500, or 2,000 μL/L) for 15 min to achieve surface disinfection. Nonlethal concentrations of egg disinfectants were also evaluated for their germicidal effects by culturing disinfected eggs in sterile Bacto Tryptic Soy Broth. The hatching success of the eggs treated with tannic acid (at all concentrations) was not different from that of the controls. Disinfecting eggs with H2O2 (all doses) and low doses of calcium hypochlorite (25–75 mg/L) or PVP-I (25 mg/L) did not reduce embryo survival, but exposure to calcium hypochlorite and PVP-I at higher concentrations (100 mg/L and 50, 75, or 100 mg/L, respectively) was lethal. In the first dis...

Characterizing ovarian gene expression during oocyte growth in Atlantic cod (Gadus morhua).

Vertebrate oocytes undergo dramatic changes during development as they accumulate many RNA transcripts, glycoproteins, and yolk proteins, necessary to ensure proper fertilization and embryogenesis. Oogenesis in teleosts often requires several years for completion, but very little is known about the early developmental stages. Recently, two-stage gene expression comparisons were made during oocyte growth in coho salmon (Oncorhynchus kisutch) and Atlantic cod (Gadus morhua), but more broad-scale, comprehensive assessments have not been conducted. The objectives of the present study were to characterize the gene expression patterns throughout oocyte growth in cod and compare them to changes previously identified in coho salmon. A quantitative PCR survey was conducted using 50 genes at six ovarian stages, ranging from the onset of primary growth (oocyte differentiation) to late vitellogenesis. Most expression patterns could be grouped into three major clusters, consisting of oocyte-derived (cluster 1) and likely follicle cell (clusters 2 and 3) genes. Oocyte genes were elevated during primary growth, while many follicle cell transcripts were abundant during oocyte differentiation and vitellogenesis. Few expression changes identified in coho salmon were evident in cod, which is likely due to differences in reproductive strategies. These results demonstrate that dynamic changes in gene expression occur during oocyte growth in teleost fish.

Spawning, Larviculture, and Salinity Tolerance of Alewives and Blueback Herring in Captivity

AbstractPrecipitous declines in wild populations of river herring species (Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis) have led to increased interest in stock enhancement efforts. Additionally, their popularity as a baitfish among recreational anglers has generated interest in commercial production of these species for marine baitfish markets. The objective of this investigation was to elucidate practical culture protocols for captive propagation of these species for commercial and restoration purposes. Wild Blueback Herring, captured during their annual spawning migration, spawned in tanks volitionally, while Alewives required exogenous hormone administration. Larvae of both species were successfully raised through metamorphosis using a feeding regime comprised of enriched rotifers followed by Artemia nauplii and a commercially available diet. Survival of early larvae acclimated to salinities ranging from 5‰ to 15‰ was high for both species (>94.0%) while that for older larvae accli...

Brain aromatase (cyp19a1b) and gonadotropin releasing hormone (gnrh2 and gnrh3) expression during reproductive development and sex change in black sea bass (Centropristis striata)

Teleost fish exhibit diverse reproductive strategies, and some species are capable of changing sex. The influence of many endocrine factors, such as gonadal steroids and neuropeptides, has been studied in relation to sex change, but comparatively less research has focused on gene expression changes within the brain in temperate grouper species with non-haremic social structures. The purpose of the present study was to investigate gonadotropin releasing hormone (GnRH) and brain aromatase (cyp19a1b) gene expression patterns during reproductive development and sex change in protogynous (female to male) black sea bass (Centropristis striata). Partial cDNA fragments for cyp19a1b and eef1a (a reference gene) were identified, and included with known gnrh2 and gnrh3 sequences in real time quantitative PCR. Elevated cyp19a1b expression was evident in the olfactory bulbs, telencephalon, optic tectum, and hypothalamus/midbrain region during vitellogenic growth, which may indicate changes in the brain related to neurogenesis or sexual behavior. In contrast, gnrh2 and gnrh3 expression levels were largely similar among gonadal states, and all three genes exhibited stable expression during sex change. Although sex change in black sea bass is not associated with dramatic changes in GnRH or cyp19a1b gene expression among brain regions, these genes may mediate processes at other levels, such as within individual hypothalamic nuclei, or through changes in neuron size, that warrant further research.