40 DECEMBER 2013 • WORLD AQUACULTURE • WWW.WAS.ORG muscle development and decreased protein turnover in studied tissues, genetic diversity within families can be exploited to allow selection of better-adapted or superior fish that thrive on the improved feed or alternative feed formulations aimed at replacing fishmeal in commercial diets. This will also allow the potential development of a transcriptome of genes in hybrid striped bass. Improved Efficiency in Larval Fish Production Scientists at the SNARC are developing feeds for first-feeding larval and small juvenile Morone species to improve growth and survival and reduce production costs. Methods include identifying novel forms of key nutritional components and means of delivery. Alternative production methods for larvae also are being evaluated, including means to reduce cannibalism and predation, and the use of light and other sensory characteristics to increase feed intake. Scientists have completed two recent experiments in this area. The first investigated the use of greenwater versus clearwater culture methods to evaluate larval growth of hybrid striped bass (McIntire and Riche 2013). Another greenwater experiment was conducted with fry from a fall spawn, which determined the optimum amount of algae to improve survival in hybrid striped bass fry culture and what impact it had on fry growth (Fig. 6). There is great interest in this area and impact across cultured fish species. This research will improve early weaning diets for hybrid striped bass through current and future larval feeding studies. Current and future work will save money on water treatments, improve feeding regimes, culture methods, and improve survival, uniformity, and growth of fry. In conjunction with larval studies, the histidine requirement of juvenile striped bass and evaluation of different varieties of soybean meal on growth and intestinal morphology in juvenile hybrid striped bass are being investigated. Both studies may assist in formulation of reduced-fishmeal or fishmeal-free diets for hybrid striped bass in the future which could reduce feed costs for producers and allow for domestic industry expansion and production. Disease Control in Aquaculture Scientists at SNARC have evaluated the efficacy, toxicity, human food safety and target animal safety of copper sulfate in channel catfish for the control of Ich on foodfish and fungus on eggs in support of an application for FDA approval. They have also collaborated on international research using peracetic acid to investigate the effectiveness of this new therapeutant to control various aquatic pathogens. Recent research also demonstrated pretreatment with copper sulfate can prevent columnaris disease when risk of disease is greatest, such as seining ponds, grading fingerlings and hauling fish to grow-out facilities, and that white bass are more resistant to the disease than sunshine bass (Morone chrysops × M. saxatilis). Another research focus includes toxicity studies on therapeutic compounds used for disease control to know the sensitivity of fish to specific compounds. Developing comparative data for each compound and the information can be used to make safe, effective, and accurate treatment recommendations for the industry. Tested compounds included potassium permanganate (tilapia, channel catfish and sunshine bass); copper sulfate (channel catfish fingerlings and fry, sunshine bass, tilapia); peracetic acid (channel catfish fry, grass carp, tilapia and sunshine bass); isopropyl methylphosphonic acid (eggs and fry of golden shiner and channel catfish); and rotenone (freshwater shrimp). Research has been conducted in support of gaining FDAapproval for copper sulfate as a treatment of Ich on channel catfish in earthen ponds and for fungus on catfish eggs. Proving the safety of a compound is essential to the approval process for a new animal drug. Results show that it is safe to treat channel catfish with copper sulfate. Likewise, treatments for fungus (Saprolegnia spp.) control on catfish eggs are expensive and have potential health issues for hatchery personnel, so scientists conducted experiments on use of copper sulfate to treat channel catfish eggs. Treatment limits fungus, improves survival and is safe for catfish eggs, findings that economical option for producers to use. The cost of chemicals to treat a typical hatchery with 300 hatching troughs during the spawning season is much less using copper sulfate ($35) than hydrogen peroxide ($1370) or formalin ($2155). Furthermore, copper sulfate is more effective than potassium permanganate in treating columnaris disease. Columnaris is the most prevalent disease in the commercial catfish farming (Fig. 7) and is a problem with other warmwater species, such as sunshine bass. Farmers use potassium permanganate as a suitable pond TOP, FIGURE 6. Twenty-day-post-hatch hybrid striped bass fry from the same tank (6.3x). BOTTOM, FIGURE 7. Channel catfish infected with columnaris.
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