2010 Annual Report 1a.Objectives (from AD-416) Discovery and primary development of novel natural or natural product-based compounds for controlling undesirable microbes and off-flavors in aquaculture and to determine the optimal management approaches of new and current algicides and bactericides for controlling undesirable microbes and off-flavors in aquaculture. 1b.Approach (from AD-416) Conduct bacterial and cyanobacterial bioassays to identify natural or natural product-based compounds as potential leads for use in managing diseases and as selective algicides to control environmentally-derived off-flavors in catfish aquaculture. Efficacy testing of the most promising compounds will be performed using aquaria, limnocorrals, and in replicated pond studies. Perform replicated pond studies to determine the holding period required to permit off-flavor catfish to become on-flavor after applications of algicides to ponds to remove off-flavor cyanobacteria. Perform primary development of promising natural compounds identified from bacterial and cyanobacterial bioassays for use as therapeutic drugs and selective algicides to manage common catfish diseases, improve catfish health, and improve product quality. 3.Progress Report This is the final report for the project 6408-41000-005-00D terminated in October, 2009. There was a period of one month between the beginning of FY 2010 and the termination date for the project occurring at the end of October. No experiments were initiated in the timeframe corresponding to this project. Substantial results were realized over the 5 years of the project. A rapid bioassay was utilized in conjunction with bioassay-guided fractionation to evaluate thousands of samples including crude extracts (from plants and marine organisms), crude extract fractions, and pure compounds to discover selectively toxic compounds towards odor-producing species of cyanobacteria (blue-green algae) that are contributors to “musty” off-flavor problems in pond-raised channel catfish. During collaborative research with a commercial partner, primary development of a patented algaecidal compound found in ryegrass resulted in the discovery of a more cost-effective method to manufacture the algaecidal compound. Collaborative research with scientists at Mississippi State University, Stoneville, Mississippi, demonstrated the efficacy of the patented algaecidal compound in reducing the abundance of musty odor-producing species of cyanobacteria in the water of catfish production ponds and subsequently reducing the musty off-flavor in the catfish flesh. The microbial source of musty off-flavor in channel catfish raised in east Mississippi and west Alabama ponds was discovered to be the same species of cyanobacteria previously identified as the main cause of musty off-flavor in west Mississippi pond-raised channel catfish. During collaborative research with scientists at the University of California-Davis, the microbial metabolites geosmin and 2-methylisoborneol were found to be responsible for “earthy” and musty off-flavors in arctic char and sturgeon cultured in recirculating aquaculture systems (RAS). A rapid bioassay was developed to discover environmentally safe natural compounds for use as therapeutants against the most common disease-producing bacteria of pond-raised channel catfish. The discovery of bactericidal compounds is the first stage in providing producers with novel therapeutants as alternatives to current management approaches (e.g., use of antibiotic-laden feed) for controlling these diseases. Using this rapid bioassay, several natural compounds produced by certain plants were discovered to selectively inhibit the growth of the bacterial species responsible for the most common diseases of pond-raised channel catfish. Because pre-harvest off-flavor problems persist in many types of aquaculture products (e.g., finfish raised in recirculating aquaculture systems), the new Project No. 6408-41000-009-00D incorporates research to discover and develop solutions and management practices to help producers mitigate these types of off-flavor problems. In addition, Project No. 6408-41000-009-00D continues research to discover environmentally safe natural compounds for use as therapeutants against common disease-causing bacteria in pond-raised channel catfish. Review Publications Schrader, K., Dayan, F.E. 2009. Antioxidant Enzyme Activities in the Cyanobacteria Planktothrix Agardhii, Planktothrix Perornata, Raphidiopsis Brookii, and the Green Alga Selenastrum Capricornutum In Handbook on Cyanobacteria. P.M. Gault and H.J. Marler, eds., Nova Science Publishers, Inc., Hauppauge, NY. PP. 474-483. Purcaro, R., Schrader, K., Burandt, C., Dellagreca, M., Meepagala, K.M. 2009. Algicide Constituents from Swinglea glutinosa. Journal of Agricultural and Food Chemistry. 57:10632-10635. Schrader, K., Summerfelt, S.T. Distribution of Off-Flavor Compounds and Isolation of Geosmin-Producing Bacteria in a Series of Water Recirculating Systems for Rainbow Trout Culture. North American Journal of Aquaculture. 72:1-9.