Phytase supplemented diets do not reduce the abundance of cyanobacteria and common off-flavor compounds in hybrid striped bass (Morone chrysops x M. saxatilis) aquaculture ponds

ABSTRACT

Freshwater fish grown in earthen ponds in the southeastern US can acquire “earthy” and “musty” taints due to the bioaccumulation of the cyanobacteria metabolites geosmin and 2-methyisoborneol (MIB) in the fish flesh and result in unmarketable fish. Dense cyanobacteria communities occur because nutrient inputs (phosphorus) are high in fish production ponds due to high feed application rates. In this study, hybrid striped bass (Morone chrysops x M. saxatilis) grown in earthen ponds was offered one of the six diets including diets supplemented with phytase to reduce phosphorus input to the pond and the subsequent intention of reducing the abundance of undesirable cyanobacteria. Water samples collected biweekly from each pond were analyzed for phytoplankton community structure and concentrations of geosmin and MIB. Differences in dietary phosphorus consumption among diets did not significantly affect soluble reactive phosphorus and total phosphorus concentrations, cyanobacteria abundance, and geosmin and MIB concentrations in pond water.

KEYWORDS:

• Cyanobacteria
• geosmin
• hybrid striped bass
• 2-methylisoborneol
• off-flavor

Acknowledgments

The experimental protocol was approved by the HKDSNARC Institutional Animal Care and Use Committee and conformed to ARS Policies and Procedures 130.4 and 635.1.

We thank Skretting USA for providing the diets used in this study and Jackie Zimmerman, Skretting USA, for all her assistance; Dr Karthik Massagounder, Evonik Industries, Essen, Germany, for providing the amino acids; Dr Craig Wyatt, AB Vista Inc., Plantation, FL USA, for providing the phytase and critical analytical lab support; Dr T. Gibson Gaylord, US Fish and Wildlife Service, Bozeman, MT, for assistance with diet formulation. We also thank the following USDA-ARS personnel for their substantial assistance during the study: Matt Barnett, Jeff Bouscher, Jason Brown, Bradley Farmer, Logan Fortune, Paxton Harper, Dewayne Harries, Robert Ideker, George Huskey, Cindy Ledbetter, Joel Ledbetter, Phaedra Page, Garrett Ponder, Candis Ray, Rebecca Roberts, Dana Shurtleff, Carl Webster, and River Williams.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the United States Department of Agriculture (USDA). Mention of trade names is for descriptive purposes only and does not imply endorsement or approval by the USDA to the exclusion of other products that may also be suitable. The USDA is an equal opportunity provider and employer.

Disclosure statement

No potential conflict of interest was reported by the author(s).