2007 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 Additional plant extracts, including a large number of aquatic plant extracts, were evaluated using a rapid bioassay to discover promising natural algicides. A rapid antibacterial bioassay was used to evaluate natural compounds, crude extracts from plants, and extract fractions to discover antibacterial compounds to help manage the most common bacterial diseases in catfish aquaculture. One natural compound was discovered to have significant antibacterial activity towards the two common catfish disease-causing bacteria. This natural compound was determined to be highly water-soluble and environmentally safe, important qualities to be met before further evaluation of its potential use as a therapeutant in channel catfish aquaculture. The compound responsible for earthy off-flavor in Arctic char and sturgeon cultured in recirculating aquaculture systems (RAS) was identified. Research was initiated to develop approaches for managing this off-flavor problem in RAS. 4.Accomplishments Natural Compound Inhibits Two Common Catfish Disease-causing Bacteria The research objective is to discover natural compounds that are environmentally safe and effective alternatives to current management approaches (e.g., medicated feed containing antibiotics) for two common bacterial diseases of pond-raised channel catfish. During the first stage of the discovery process, compounds are evaluated using a laboratory bioassay. A natural compound was found to inhibit the growth of both types of disease-causing bacteria. This natural compound may be useful as a therapeutant to help manage and prevent these common bacterial diseases in cultured catfish. National Program 106 Component: Integrated Aquatic Animal Health Management-Mechanism of Disease. 5.Significant Activities that Support Special Target Populations None 6.Technology Transfer Number of active CRADAs and MTAs 1 Number of non-peer reviewed presentations and proceedings 2 Review Publications Mireles Dewitt, C., Kleinholz, C.W., Vann, D.G., Bilby, C.A., Thomas, S., Schrader, K. Evaluation of Acid and Alkaline Processing to Remove Muddy Off-Flavors in Channel Catfish (Ictalurus punctatus). Journal of Aquatic Food Product Technology. 16(2):77-90.