Impact of diuron applications to commercial catfish ponds on musty-odor cyanobacteria, musty off-flavor compound concentrations, and channel catfish fillet flavor quality

Authors: Schrader, Kevin

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2021
Publication Date: 1/11/2022
Citation: Schrader, K. 2022. Impact of diuron applications to commercial catfish ponds on musty-odor cyanobacteria, musty off-flavor compound concentrations, and channel catfish fillet flavor quality. North American Journal of Aquaculture. 84:149-155. https://doi.org/10.1002/naaq.10225.
DOI: https://doi.org/10.1002/naaq.10225

Interpretive Summary: “Musty” off-flavor in pond-raised catfish can result in an unpalatable and unmarketable product for catfish farmers in the southern United States. Certain types of cyanobacteria (blue-green algae) in the catfish ponds produce a musty odor compound which accumulates in the catfish flesh and causes musty off-flavor. One approved algicide is diuron for the specific management of the type of cyanobacteria that produces the musty odor compound. In this study, three commercial ponds previously determined to contain musty off-flavor catfish were monitored over approximately 2 months to determine the impact and pattern of weekly diuron applications on the abundance of the musty odor-producing cyanobacteria, green algae, concentrations of the musty odor compound in the pond water, and flavor characteristics of the sampled catfish collected during the treatment period. After several diuron applications to each pond, the abundance of the musty odor-producing cyanobacteria and concentrations of the musty compound in pond water decreased dramatically. Catfish in each pond were determined to be “on-flavor” approximately 2 months after the initial diuron application. This study demonstrated that diuron applied via label-specified treatment protocols provide catfish farmers with a practical and cost-effective management approach for the musty odor-producing cyanobacteria and subsequent musty-related off-flavor.

Technical Abstract: “Musty” off-flavor in pond-raised catfish can result in an unpalatable and unmarketable product for catfish farmers in the southern United States. Certain species of cyanobacteria (blue-green algae) in the catfish ponds produce 2-methylisoborneol (MIB) which accumulates in the catfish flesh and causes musty off-flavor. One management approach available to United States catfish farmers is the application of algicides to ponds to reduce the abundance of noxious cyanobacteria. Diuron is one approved algicide to specifically manage MIB-related off-flavor caused by the common cyanobacterium Planktothrix perornata f. attenuata. In this study, three commercial ponds previously determined to contain musty off-flavor catfish were monitored over approximately 2 months to determine the impact and pattern of weekly diuron applications on the abundance of P. perornata, chlorophytes (green algae), MIB concentrations in the pond water, and flavor characteristics of the sampled catfish collected during the treatment period. After several diuron applications to each pond, the abundance of P. perornata and MIB concentrations in pond water decreased dramatically. Catfish in each pond were determined to be “on-flavor” approximately 2 months after the initial diuron application. This study demonstrated that diuron applied via label-specified treatment protocols provide catfish farmers with a practical and cost-effective management approach for P. perornata and subsequent MIB-related off-flavor.