1a. Objectives (from AD-416)
Objective 1: Characterize genetic and phenotypic contributions of important production traits for Morone broodstock management and improvement. Sub-Objective 1A. Produce experimental hybrid striped bass families. Sub-Objective 1B. Assess the genetic basis of phenotypic variation of growth in hybrid striped bass. Sub-Objective 1C. Evaluate the performance of hybrid striped bass families under alternate stocking rates. Objective 2: Refine nutrient requirements, evaluate alternate sources of protein, and develop practical feed formulas for Morone culture. Sub-Objective 2A. Refine essential amino acid requirements of advanced juvenile hybrid striped bass using practical ingredients. Sub-Objective 2B. Improve the performance of commercial hybrid striped bass diets in which fish meal is replaced with by-products of poultry processing or a blend of plant products. Sub-Objective 2C. Develop practical feed formulas for hybrid striped bass culture. Objective 3: Develop strategies to improve production system efficiency. Sub-Objective 3A. Define stocking rate/biomass-yield relationship in a mixed suspended growth production system. Sub-Objective 3B. Compare catfish yields in a mixed suspended growth production system scaled up to ponds.
1b. Approach (from AD-416)
Identify and characterize genetic variation in commercially relevant traits of white and striped bass and implement a breeding program to develop superior hybrid striped bass parental breeding stocks. Evaluate growth performance of half-sibling families of hybrid striped bass reared communally in earthen ponds. Evaluate the performance of hybrid striped bass families under alternate stocking rates. Define requirements for hybrid striped bass for first-limiting indispensable amino acids in all plant protein diets. Evaluate amino acid supplementation for hybrid striped bass diets in which fish meal is replaced by alternative feed ingredients. Develop and evaluate in aquaria and tank culture, and validate in earthen pond culture diets for hybrid striped bass formulated with alternative feed ingredients. Evaluate the effects of stocking density, feeds and feeding strategies, and environmental conditions on survival and growth of hybrid striped bass and catfish in tanks and earthen ponds. Evaluate novel, intensive production technology in tanks and earthen ponds.
3. Progress Report
We conditioned broodstock and produced 24 half-sib sunshine bass crosses that yielded 482,000 larvae, and 13 half-sib white bass crosses that yielded 116,000 larvae. Broodstock for the next phase of spawning are being conditioned. In collaboration with the University of Arkansas at Pine Bluff, larval samples from each of the 24 half-sib families of sunshine bass and 13 half-sib families were taken just after hatching and prior to onset of feeding for analysis of the role that maternal size and age have on sunshine and white bass larvae and fingerlings. Also, ovarian condition pre- and post-hormone injection wass assessed by ultrasonography. We initiated a study to examine gene expression profiles within the testis and ovary of white bass and striped bass juveniles and broodstock. At least 10 different gene targets have been examined, and the expression levels of these genes are being correlated to gonad stage and quality as determined by histological analysis. We compared how sunshine bass, and their parent species white bass and striped bass, responded to low oxygen levels using extracellular flux technology, the first application of this technology in fish; we documented key metabolic differences between species. We completed dose-response tank trials to examine the effects of elevated water temperature on the optimum dietary protein, dietary fat, and feeding intensity in hybrid striped bass. We conducted a study to determine the optimum dietary lysine level in commercial-grade fishmeal-free diets fed to mixed families of hybrid striped bass in order to assess performance differences among strains fed high-plant protein diets. In collaboration with University of Arkansas at Pine Bluff researchers, we conducted feeding trials to assess the impact on channel catfish production of substituting standard soybean oil, soybean oil with conjugated linoleic acids, or algal n-3 fatty acid for menhaden fish oil in feed. In collaboration with ARS Trout Grains Project, Hagerman, ID, and USFWS Feed Technology Center, Bozeman, MT, scientists, we developed nutrient composition and digestibility coefficients for a variety of novel ingredients in feeding trials for hybrid striped bass and rainbow trout that are being assembled by the ARS Office of Technology Transfer for dissemination. We completed a study to quantify the growth response in earthen ponds of the channel x blue hybrid catfish to daily exposure during the summer growing season to different minimum dissolved oxygen concentrations and initiated a similar study for hybrid striped bass fingerlings. In collaboration with scientists at the ARS Natural Products Utilization Research Unit, Oxford, MS, and University of Arkansas at Pine Bluff we completed a study to evaluate the development of phytoplankton communities and common off-flavors in a biofloc technology system used for growing channel catfish and initiated a follow-on study to investigate bacterial sources of common off-flavors in this system. Quantification of the density-yield relationship for channel catfish grown in a biofloc technology production system continued, with one study completed and a follow-on study initiated.
1. Parents influence performance of hybrid bass. Using non-selectively bred parents to produce Sunshine bass (cross between female white bass and male striped bass) results in large variations in fish growth. In a study conducted at the Harry K. Dupree Stuttgart National Aquaculture Research Center, Stuttgart, AR, scientists identified significant sire and dam components of variation in studied growth traits. Additionally, the researchers showed that compared to a stable control gene, genes involved in growth were more active and genes involved in metabolism, breakdown, and usage of fats were less active in the faster growing families than in the slower growing families. These gene assays will be used in the future to predict how families might grow under similar production settings. The increased understanding of the genetic basis of production traits will contribute to an improved selection program to develop a faster growing Sunshine bass.
2. New genetic markers developed for Sunshine bass. In selecting for a faster growing Sunshine bass it would be helpful to have a more efficient method to distinguish faster growing from slower growing fish. One possibility is genetic analysis to discover the controlling mechanisms and identify genetic markers for growth. From a transcriptome (the functional portion of the genome) of nearly 40,000 genes, scientists at the Harry K. Dupree Stuttgart National Aquaculture Research Center, Stuttgart, AR, identified a number of genes that were expressed differently by faster as opposed to slower growing Sunshine bass. Additionally, they identified hundreds of thousands of single nucleotide polymorphisms for potential use in marker-assisted selection programs. Scientists and breeders can use this information to better understand the controlling mechanisms of growth differences and to use these markers to speed identification of superior broodfish and decrease the number of fish needed for a breeding program.
3. From the laboratory bench to the pondside: Modeling aquaculture stressors in fish cells. Farmed fish, including hybrid striped bass, frequently are exposed to numerous environmental stressors such as high temperature, low oxygen, and poor water quality that can affect fish metabolism negatively, ultimately resulting in poor growth and increased disease susceptibility. To better understand how stress specifically affects cellular metabolism in fish, researchers at the Harry K. Dupree Stuttgart National Aquaculture Research Center, Stuttgart, AR, investigated the metabolic responses of cells derived from three important species of warmwater fish to rapid temperature increases and to compounds that inhibited respiration. This was the first use of extracellular flux technology on fish cells and led to the discovery that each cell type responds uniquely to stressors. The metabolic 'signatures' generated from these responses will be employed as novel biomarkers to predict how fish may cope with stress encountered in production settings.
4. Hybrid catfish production linked to pond dissolved oxygen concentration. Hybrid catfish (cross between female channel catfish and male blue catfish) are an increasingly popular culture fish for which pond management strategies are still being developed. Managing pond dissolved oxygen concentration in catfish production ponds at night during the growing season requires great effort. Scientists at the Harry K. Dupree Stuttgart National Aquaculture Research Center, Stuttgart, AR, conducted an intensive study that demonstrated that hybrid catfish growth and yield in ponds were greater at higher nightly dissolved oxygen concentrations. Hybrid catfish in ponds where nightly dissolved oxygen concentration was higher consumed more feed on a daily basis. Higher feed consumption increased fish yield with no loss in growth efficiency. Identifying an optimal pond dissolved oxygen management strategy is an important factor in ensuring sustainable catfish production in the United States.
5. Biofloc technology production system reduces off-flavor in channel catfish. Certain species of cyanobacteria (blue green algae) are undesirable in earthen channel catfish ponds because they produce odorous compounds that can accumulate in the flesh of fish and subsequently result in an 'off-flavor' and unmarketable product. Studies have shown that a novel, highly intensive production system, called the biofloc technology production system, produces high yields of channel catfish, but its impact on the development and composition of algal communities and related off-flavor problems is unexplored. A collaborative study by ARS scientists at the Harry K. Dupree Stuttgart National Aquaculture Research Center, Stuttgart, AR, and the Natural Products Utilization Research Unit, Oxford, MS, and a scientist at the University of Arkansas at Pine Bluff, did not detect off-flavor producing cyanobacteria and found that concentrations of two common off-flavor compounds were far below those that can occur in aquaculture ponds in the southeastern US. A catfish production system where the occurrence of off-flavor is minimized would contribute to increased productivity and profitability of catfish culture.
Green, B.W., Perschbacher, P., Ludwig, G.M., Duke, S.E. 2010. Threadfin shad impacts phytoplankton and zooplankton community structures in channel catfish ponds. Aquaculture Research. 41:e524-e536.