Walleye is a niche-market species that has potential for profitable production in recirculation aquaculture systems (RAS). Little information is available regarding feeding alternate ingredient, fishmeal-free diets to walleye. This study was conducted to compare the effects of feeding a fishmeal-free diet versus a traditional fish-meal based diet on walleye performance, water quality, and waste production in replicate RAS. Specially formulated fishmeal-free (FMF) and fishmeal-based (FM) diets were fed to walleye. The FMF diet used proteins derived from poultry meal, soy protein concentrate, and corn protein concentrate, and lipids from menhaden oil and poultry oil. The FM diet used proteins from fishmeal, poultry meal, soybean meal, and blood meal, and lipids from menhaden oil. Each diet was formulated with a protein/ fat ratio of approximately 42/18. The study began when fish were 85 g and continued for 9 months.
Walleye performance was similar (P > 0.05) between the FMF and FM diets: mean fish weight at study’s end was 589 ± 15 and 571 ± 26 g; and feed conversion ratio was 1.27 ± 0.03 and 1.32 ± 0.02, respectively. Survival was > 98.5 % for both treatments. Of interest, phosphorous levels were more than two times greater and nitrogen was significantly greater (P < 0.05) in RAS water where walleye were fed the FM diet. Of interest is that the reduced phosphorous discharge related to feeding this fishmeal-free diet could increase the feasibility of growing walleye in commercial facilities AND meeting stringent water quality discharge standards