Off-flavors in pond-grown ictalurid catfish: causes and management options

Authors: Tucker, Craig; Schrader, Kevin

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2019
Publication Date: 2/7/2020
Citation: Tucker, C.S., Schrader, K.K. 2020. Off-flavors in pond-grown ictalurid catfish: causes and management options. Journal of the World Aquaculture Society. 51:7-92.

Interpretive Summary: Channel catfish and hybrid catfish grown in earthen ponds in the southeastern United States often acquire undesirable off-flavors prior to harvest. Fish processors evaluate all fish for flavor quality before harvest and off-flavored fish are not accepted for processing. Harvest delays caused by off-flavors impose a significant cost to farmers. Most summertime off-flavors are caused by odorous (but not harmful) substances produced by blue-green algae. Other off-flavors may be acquired when fish forage on dead organic matter, particularly during winter months when catfish are not fed manufactured feeds. Managing off-flavors in pond-grown fish is difficult because the warm, hypereutrophic environment of catfish ponds makes them ideal habitats for odor-producing blue-green algae. Co-culturing plankton-eating fish with catfish reduces the incidence of off-flavor, but other strategies to prevent off-flavors have generally failed or are economically impractical. Most catfish farmers do not attempt to prevent problems, but rather they assess fish flavor a few weeks before harvest and if fish are found to be off-flavored, farmers attempt to kill odor-producing blue-green algae with algicides. Once the odor-producing organisms are killed, the taint purges from fish at rates dependent on water temperature and fillet fat content. This paper reviews the causes of off-flavor in catfish, the ecology of blue-green algae in catfish ponds, and numerous strategies proposed for preventing or treating off-flavors. A decision-making scheme based on knowledge gained in research is presented as a guide to effective use of the limited tools available to manage off-flavors.

Technical Abstract: Ictalurid catfish grown in earthen ponds in the southeastern United States often acquire undesirable off-flavors prior to harvest and are unacceptable for processing until flavor improves. Harvest delays caused by off-flavors impose a significant cost to farmers and considerable research has been conducted to determine the causes and management of fish taints. Most summertime off-flavors are caused by the cyanobacterial secondary metabolites 2-methylisoborneol or geosmin. Biomanipulation using planktivorous fish can reduce the incidence of odorous cyanobacterial populations, but other strategies to prevent off-flavors have generally failed or are economically impractical. Most catfish farmers do not prevent off-flavors but rather they assess fish flavor a few weeks before harvest and if fish are found to be off-flavored, they attempt to eradicate odor-producing cyanobacteria with algicides. Once the odor-producing organisms are killed, the taint purges from fish at rates dependent on water temperature and fillet fat content. This paper reviews the causes of off-flavor in catfish, the ecology of cyanobacteria in catfish ponds, and numerous strategies proposed for preventing or treating cyanobacterial (and other) off-flavors. A decision-making scheme based on knowledge gained in research is presented as a guide to effective use of the limited tools available to manage off-flavors.