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Kim J.-H.,Center for Aquaculture and Environmental Research | Dahms H.-U.,Sangmyung University | Han K.-N.,Inha University
Aquaculture Research

The river pufferfish Takifugu obscurus is one of the most valuable aquaculture species in South Korea and China. To analyse the effect of rearing densities in the aquaculture of this species, we performed an experiment where T. obscurus was reared for 3 months after hatching at different initial rearing densities (10 fish L-1, 20 fish L-1, and 25 fish L-1) which are similar to rearing densities in aquaculture (10-15 fish L-1). The growth of the high density group (25 fish L-1) was significantly slower than that of the low density group. To determine biomarkers for stress under conditions of high rearing density, we chose six stress-related genes (heat shock proteins (HSPs) 70 and 90β, metallothionein (MT), cytochrome P450 1A (CYP1A), glucocorticoid receptor (GCR) and phosphoenolpyruvate carboxykinase (PEPCK) and evaluated their expression by real-time reverse transcript polymerase chain reaction (real-time RT-PCR). In the high density group, we observed significant up-regulation of genes encoding HSPs 70 and 90β, MT, CYP1A, and PEPCK in liver and brain, but no up-regulation of the GCR. In particular, expression of HSP70, MT and CYP1A was up-regulated in a tissue-specific pattern. Our results demonstrate that growth retardation at high initial rearing densities is associated with stress-induced gene expression. These findings further indicate that molecular biomarkers can be useful to determine the optimal rearing conditions with respect to densities of pufferfish culture. © 2012 John Wiley & Sons Ltd. Source

Shrimpton J.M.,University of Northern British Columbia | Heath J.W.,Yellow Island Aquaculture Ltd. | Devlin R.H.,Center for Aquaculture and Environmental Research | Heath D.D.,University of Windsor

The use of triploid salmon for aquaculture is attractive as they do not mature sexually, limiting losses associated with poor flesh quality in mature fish and posing less genetic risk to wild stocks if they escape. Inconsistent survival and growth performance in triploid fish, however, has limited their implementation. In our study, ocean-type Chinook salmon (Oncorhynchus tshawytscha) were bred using replicated 3×3 factorial mating designs to create 18 families to test whether triploidization resulted in changes in growth and ionoregulation performance in freshwater and seawater. Eggs were pressure shocked after fertilization to create triploid offspring in a subset of each family. In spring, freshwater fish were sampled for size and gill Na +, K +-ATPase activity. Plasma chloride and cortisol were measured following a 24-h saltwater challenge. Growth performance was monitored for a further four months following transfer to sea water. We found significant effects of ploidy and sire (paternal effect) on smolt weight, as well as on gill Na +, K +-ATPase activity, although the latter did not correspond with performance in a 24-h saltwater challenge. Following four months of ocean growth, diploid animals were consistently larger, with greater circulating levels of insulin-like growth factor-1 than triploid sibs, although specific growth rates did not differ. Conversely, gill Na +, K +-ATPase activity at that time was significantly higher in triploid than diploid fish. When the phenotypic variance for the various traits was partitioned, triploids exhibited significantly greater additive genetic variance and maternal effects across all traits relative to diploid fish - indicating that gene dosage effects were primarily additive. The strong family effect indicates that genotype has a substantial role in determining the effects of ploidy manipulation on ionoregulatory and growth performance in Chinook salmon. © 2011 Elsevier B.V. Source

Kawakami Y.,Hokkaido University | Saito T.,Hokkaido University | Fujimoto T.,Hokkaido University | Fujimoto T.,Center for Aquaculture and Environmental Research | And 5 more authors.

Primordial germ cells (PGCs) are the only cells in developing embryos with the potential to transmit genetic information to the next generation. We previously visualized the PGCs of several teleostean embryos by injecting RNA synthesized from constructs encoding green fluorescent protein (GFP) fused to the 3'UTR of the zebrafish (Danio rerio) nanos1 gene (nos1). However, this technique was not always suitable for visualizing PGCs in embryos from all teleost species. In this study, we compared the visualization of PGCs in common carp (Cyprinus carpio) embryos using two artificial constructs containing GFP fused to the 3'UTR of nanos from either common carp or zebrafish. Visualization was better using GFP fused to the 3'UTR of the nanos gene from common carp, compared with that from zebrafish. The visualized PGCs successfully migrated toward the gonadal ridge after transplantation into goldfish host embryos, suggesting that they maintained normal migratory motility. These techniques could be useful for the production of inter-specific germline chimeras using common carp donor PGCs. © 2011 Elsevier B.V. Source

Callan C.K.,The Oceanic Institute | Laidley C.W.,The Oceanic Institute | Forster I.P.,The Oceanic Institute | Forster I.P.,Center for Aquaculture and Environmental Research | And 3 more authors.
Aquaculture Research

This study was conducted to determine the effects of broodstock diet on flame angelfish (Centropyge loriculus) reproduction and generate baseline spawning performance (mean fecundity, egg fertilization, egg viability) and egg biochemistry data for this species. Sixteen flame angelfish broodstock pairs were maintained on one of three formulated diets or a raw diet (consisting of squid, shrimp, fish eggs and algae) to determine the effect of diet composition on the fecundity, egg fertilization rates and egg viability over a 7-month period. Although all the diets supported similar mean spawn frequency and fecundity over the duration of the experiment, the mean fertilization rates and egg viability were significantly greater among pairs receiving the raw diet. Egg fatty acid composition was generally reflective of the maternal diet and similar to the values reported for other tropical species. In particular, dietary factors such as n-3 highly unsaturated fatty acid and ARA level (which were elevated in the raw diet and eggs from fish receiving that treatment) are correlated with egg quality and are therefore worthy of future investigation. Because of the ease of conditioning, adaptability to varied formulated diets and continuous, sustained reproductive output, flame angelfish are an excellent model for examining the factors affecting marine fish egg and larval quality. © 2011 Blackwell Publishing Ltd. Source

Jones S.R.M.,Canadian Department of Fisheries and Oceans | Forster I.,Center for Aquaculture and Environmental Research | Liao X.,Canadian Department of Fisheries and Oceans | Ikonomou M.G.,Canadian Department of Fisheries and Oceans

This experiment investigated a range of dietary nicarbazin concentrations for efficacy against the myxosporean parasite Kudoa thyrsites and for toxicity in seawater-reared Atlantic salmon post-smolts. Nicarbazin was incorporated into diets at 0 (control), 2.5, 5, 10 or 25gkg -1 such that each dose was replicated among three tanks and delivered intermittently over 2155degree-days. Compared with controls, the prevalence and severity of K. thyrsites, determined histologically, were significantly reduced in fish fed diets containing nicarbazin. Nicarbazin residues in skeletal muscle, liver and skin were proportional to dietary concentration between 0 and 10gkg -1 and were associated with a red discolouration of the skin. Cumulative mortality ranged from 0% to 12.4% among groups and was significantly elevated in the 10 and 25gkg -1 groups, relative to control. Weight and condition factor were reduced because of reduced feeding responses to the medicated diets. Feeding responses and appearance of the skin returned to normal and mortality ceased upon resumption of non-medicated diets. In conclusion, dietary nicarbazin was efficacious against K. thyrsites in Atlantic salmon, when included in diets at concentration of at least 2.5gkg -1. Further research will optimise nicarbazin treatment strategies and establish tissue residues following cessation of treatment. © 2012. Source

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