2012 Annual Report 1a.Objectives (from AD-416): The objective of this cooperative research project is to identify mechanisms and develop tools and methods to improve reproductive and growth efficiency of catfish. 1b.Approach (from AD-416): Continued collaborative research will be conducted to identify mechanisms for targeted enhancement of catfish reproduction and growth in order to fulfill the unit’s data collection, publication, and catfish improvement efforts. 3.Progress Report: Xenotransplantation of testicular germ cells from blue catfish to otherwise sterile channel catfish provides a unique alternative to current production methods for hybrid catfish. ARS sceintist at Stoneville, MS, and the cooperator conducted collaborative research on the xenotransplantation of spermatogonial germ cells in catfish. Blue catfish testicular cells were isolated and injected into channel catfish cohorts, and grown to maturity. Means of verifying success prior to reproduction were evaluated, however, to date have been unsuccessful. Genetic markers continue to be tested that might allow for the early determination of transplantation success. This year potential xenogenic males were dissected for sperm isolation. None of the transplanted fish had viable sperm. Further research is needed for this to be successful; however, external funding must be secured by the cooperator for the continued work on this problem. Evaluation of the regulatory aspects of feed intake is important to understanding fish growth, as growth in catfish is highly correlated to feed intake. ARS scientist and the cooperator conducted collaborative research in this area. Several suspected neuroendocrine regulators of feed intake have been identified in the catfish genome and assays developed to assess their functional expression during different nutritional states. The cooperator continues to conduct research in this field and has evaluated the direct effects of exogenous peripheral neuropeptides on feeding behavior and metabolism. This research contributes to a better understanding of the regulation of fish growth and may lead to improved management or feed formulations that will increase fish feed efficiency and profitability for the farmer.