Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Abstract only
Publication Acceptance Date: 11/1/2002
Publication Date: 12/1/2002
Citation: Zimba, P.V., Mischke, C.C., Li, M.H., Grimm, C.C. 2003. From fry to fillets: effects of water quality on optimal pond performance. 2003 Catfish Farmers of America Annual Convention and Research Symposium. February 20-22, Hilton Sandestin Beach Resort, Destin, Florida. pp. 11-12, Abstract #5. Interpretive Summary:
Technical Abstract: Current industry practices for growing catfish swim-up fry include the addition of cottonseed meal and phosphorus to stimulate algal and zooplankton blooms. Replicated experiments conducted for two years assessed pond fertilization practices for fry culture. It is clear that nitrogen, and to a lesser extent silica, should be added to these ponds to increase phytoplankton biomass and decrease cyanobacteria dominance. Additions of nitrogen (9 kg/hectare urea) and silica (140 g/hectare) twice weekly for 3 weeks prevented dominance of filamentous cyanobacteria for more than 30 (and up to 45) days. A survey of 485 production ponds during late July-August assessed the occurrence of the toxin microcystin and the off-flavor compounds beta-cyclocitral, geosmin, and 2-methylisobroneol (MIB) in the four-state production region. Beta-cyclocitral was identified in over 80% of the samples, and was correlated with presence of coccoid cyanobacteria (containing the unique pigment biomarker myxoxanthin). Geosmin was identified in fewer than 10% of ponds surveyed, whereas MIB occurred in about 35% of ponds surveyed. To assess the affects of pond age on water quality and pond ecology, water samples (10 to 11 per age group) were collected from ponds 1, 2, 3, 5, 7, 9, and 15 years post construction at a large farm having several ponds of each age. Multivariate data analyses detected several patterns: ponds less than 4 to 5 years of age had lower incidence of off-flavor relative to older ponds, and nutrient accumulation in the water column did not occur.