Location: Warmwater Aquaculture Research UnitTitle: The pond dye, Aquashade®, does not prevent cyanobacterial off-flavors in pond-grown channel catfish
|MISCHKE, CHARLES - Mississippi State University|
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2019
Publication Date: N/A
Interpretive Summary: Pond dyes are sometimes used to control the growth of underwater weeds by reducing light penetration through water. We applied a commercial pond dye four times through the summer to channel catfish ponds to determine the impacts on water quality and incidence of algae-derived off-flavors in catfish. Dye treatment had no effect on water quality, phytoplankton, or fish production. The dye did not prevent the growth of blue-green algae known to produce odorous compounds and therefore did not prevent off-flavors in catfish. The lack of a positive result is attributed to physiological adaptations of certain blue-green algae that allow them to thrive in low-light environments.
Technical Abstract: Aquashade® is a dye used to control the growth of underwater weeds by reducing light penetration through water. We applied four, monthly applications of 1 ppm Aquashade® to three Channel Catfish Ictalurus punctatus ponds during the summer growing season to determine the impacts on water quality and incidence of off-flavor in catfish. Three ponds were untreated controls. Dye treatment had no effect on nitrite or total ammonia concentrations, hours of supplemental aeration, phytoplankton standing crops, or fish production. Cyanobacteria known to produce odorous metabolites were found in all ponds at some time during the study. On the sampling date immediately before fish harvest, two ponds in each treatment contained populations of the odor-producing cyanobacterium, Planktothrix perornata, and contained fish that would not be acceptable for processing because of musty off-flavors. The mechanism of action of the dye—reducing water-column penetration of light in wavelengths of ~ 600-650 nm—will have little impact on odor-producing species of cyanobacteria because those species have physiological adaptations (non-chlorophyll accessory pigments and ability to regulate position in the water column) allowing them to thrive in low-light environments.