Submitted to: North American Journal of Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/15/2004
Publication Date: 4/29/2005
Citation: Schrader, K., Tucker, C.S., Hanson, T.R., Gerard, P.D., Kingsbury, S.K., Rimando, A.M. 2005. Management of musty off-flavor in channel catfish from commercial ponds with weekly applications of copper sulfate. North American Journal of Aquaculture. 67:138-147. Interpretive Summary: Certain types of blue-green algae produce musty compounds that accumulate in the flesh of farm-raised channel catfish in west Mississippi. This study evaluated the effectiveness of weekly low-dose applications of copper sulfate in commercial size catfish ponds to help reduce musty off-flavor in the cultured catfish. Results indicated that this management approach helped reduce off-flavor by 50% and reduced costs associated with off-flavor by 35%.
Technical Abstract: This study evaluated the effectiveness of weekly low-dose applications of copper sulfate (0.12 mg Cu/L) on the prevalence of off-flavor in catfish on commercial farms. The study was conducted over 3 years in ponds (3.2-8.4 ha) on two catfish farms in west Mississippi. Farm managers applied copper sulfate (0.5 mg copper sulfate pentahydrate/L) weekly beginning in the late spring/early summer and continued until the water temperature dropped below 20 degrees Celsius. Water samples were collected from treated and untreated ponds approximately every 3 weeks during the application period and monitored for levels of the musty compound 2-methylisoborneol (MIB), chlorophyll a, and phytoplankton community structure and abundance. In addition, catfish were caught from each study pond during the third year of the study and checked for flavor. Levels of MIB and the abundance of the MIB-producing cyanobacterium Oscillatoria perornata were significantly reduced in treated ponds compared to controls at one farm while numbers of green algae and diatoms increased significantly at both farms. Also, the overall prevalence of all types of off-flavor was reduced by 50% based upon fish flavor analysis. Based upon our results, weekly low-dose applications of copper sulfate appear to be beneficial in mitigating musty off-flavor problems in commercially produced catfish. Copper sulfate treatment reduced potential harvest delays by nearly half and reduced costs associated with off-flavor by 35%. However, the economic benefit of treatment was not statistically significant, although this likely is the result of the small dataset used for economic analyses rather than ineffectiveness of treatment.