The U.S. aquaculture industry can claim many successes, but the one truly outstanding accomplishment is the meteoric rise of the channel catfish (Ictalurus punctatus) industry. The first farming operation started in Mississippi in the late 1960's and since has developed into the leading U.S. farmed species reaching a 2007 (estimated) domestic market value of $590 million. This clearly dominates the U.S. aquaculture industry with 45% of total farm output by volume. The industry, as of late is swimming in troubled waters with inventories of food grade fish down 11% (July, 07 vs. July, 06) and culture acreage also reduced by 3%. U.S. Census Bureau data reveals that inexpensive imports of the competing fish from Southeast Asia has experienced a year-to-year increase of 97% (March, 06- March, 07) resulting in volume and price pressure. The American industry is threatened and will have to implement every possible production efficiency, political pressure and marketing program in order to thrive. The industry has identified "off flavor" as the most substantial problem facing the American catfish producers. Cyanobacteria or blue green algae blooms express geosmin and 2-methylisoborneol (MIB), which impart a muddy/earthy off flavor and smell. These two fat-soluble chemicals have been identified as the cause of the majority of the off-flavor incidents. The problem is at its height during the warm summer months and can affect 50% of the market-sized fish in inventory. This results in substantial financial hardship for the farmer, with the industry wide problem causing an estimated 60 million dollars each year. The management of off flavor is not a straightforward process and even the most careful farm managers and processors can inadvertently allow these problematic fish to enter the market. In order to quality assure/control the finished product the processors maintain tasters that will assess samples from harvest ready ponds. Once off flavor has been identified the producer has few options. The farmer can wait it out since experience has determined that it can clear up in a few days or weeks. He can treat the pond with copper sulfate or diuron to kill the cyanobacteria. The farmer can also take a more active approach and transfer the fish to a "purging" pond or raceway where they are taken off feed and held in clean well water (> 3 exchanges per day). However, it is apparent that the most damaging long term consequence of off-flavor is loss of market share to foreign competition. This puts the American farm raised catfish brand at risk. As 90% of the catfish is raised in southern states in rural areas, the loss of this market can have a significant economic impact on areas that are facing economic challenges. Effective control strategies are required to prevent off-flavor and protect the U.S. catfish industry and southern rural economies. Introducing a new product with enhanced algaecidal properties will allow U.S. farmers to remain competitive as well as provide a quality and nutritious product to the U.S. consumer. OBJECTIVES: The goal of this USDA SBIR Phase 1 grant is to develop an effective product for the control of algae that cause off-flavor in catfish. The product being researched, NM7O is proposed as an alternative to copper sulfate and diuron as an algaecide. The algaecide activity of NM7O, a manganese oxide, is due to the Mn (VII) oxidation state, a strong electron acceptor that attacks lone pairs of electrons from organic compounds containing P, S, N and O groups. We (CHK Group) have developed a patented method for inexpensively producing large, stable quantities Mn (VII) oxide. The Mn (VII) oxide in NM7O, an abbreviation for nanophase Mn (VII) oxide, is bonded to a clay carrier, which increases the products activity, reduces its manufacturing costs and provides for ease and versatility in handling, shipping and using the product. Bonding of the nanoparticles to the clay increases the particle size, thus preventing dispersion of nanoparticles. The specific objectives of the Phase 1 grant are to determine the: 1)efficacy of NM7O against blue-green algae that cause off-flavor in catfish; 2) effect of MN70 against other algal species; 3) effect of NM7O on nontarget species, and 4) effect of NM7O on catfish. Research to achieve objective 1, 2 and 3 will be completed by PhycoBiologics, Indianapolis, IN. Research to achieve objective 4 will be completed at the National Warmwater Aquaculture Center, Stoneville, MS. The product, NM7O, will be manufactured by CHK Group in Dallas, TX. Outputs from this project include a new method and product for controlling algae in ponds, specifically those that cause off-flavor in catfish. APPROACH: The project will be conducted using generally accepted laboratory procedures and published guidelines. The effect of NM7O on target and nontarget species will be determined in Objective 1, 2 and 3 and from these experiments the minimum inhibitory concentration (MIC), the median lethal concentration required to kill 50% of the population (LC50) and the dose at which there is no observed effect (NOEL) will be calculated. Regrowth studies will be conducted with the algae to estimate the percentage of cell remaining viable and determine if the compound is biostatic or biocidal. For comparison, copper sulfate and diuron will be tested at recommended concentrations. All treatments will be replicated three times and arranged in a randomized complete block design. Statistical comparisons will be made using ANOV (p=0.05). The species to be tested include: the causal agent, Oscillatoria perornata; other algal species Scenedesmus (Green), Ankistrodesmus (Green), Anabaena (Blue-Green), Pseudanabaena (Blue Green), Oedogonium (Green filamentous), Spirogyra (Green filamentous), Pithophora (Green filamentous), Chlamydomonas (Green) and Chlorella (Green); and nontarget species Daphnia magna, Acartia tonsa, Orconcetes propinquus and Penaeus vannamei. The species will be treated with nine concentration of NM7O. For objective 4 the median lethal concentration (LC50) of manganese oxide for channel catfish will be determined in 1,000 L plastic tanks containing 600 L of oxygenated pond water. Toxicity test will be arranged in a geometrically spaced series using a dilution factor of two. A range-finding test will be conducted to determine the initial treatment dose. Twenty fish (20-40 g/fish) will be placed in each tank and dosed with manganese oxide at concentration defined by the range-finding test. Fish will be observed for 5 d for death and behavioral indicators of toxicosis. Spearman-Karber analysis will be used to determine the 24 and 72-h LC50. All research with the catfish will be conducted at the Mississippi Agricultural and Forestry Experiment Station-Mississippi State University located at the National Warmwater Aquaculture Center , Stoneville, MS (NWAC) under whose auspices IACUC approval has been granted. Protocols provided in the document,"Guidelines for the Use of Fishes in Research" by the American Fisheries Society, American Institute of Fisheries Research Biologists and American Society of Ichthyologists and Herpetologists will be followed. The project will be considered successful if NM7O provides a high level of algal control and is nontoxic to nontarget species and catfish
