Walleye Sander vitreus performance, water quality, and waste production in replicated recirculation aquaculture systems when feeding a low phosphorus diet without fishmeal versus a traditional fishmeal-based diet

Authors: DAVIDSON, JOHN - Freshwater Institute; SUMMERFELT, ROBERT - Iowa State University; Barrows, Frederic; GOTTSACKER, BRANDON - North Country Clear Waters, Llc; GOOD, CHRISTOPHER - Freshwater Institute; FISCHER, GREGORY - University Wisconsin-Stevens Point-northern Aquaculture Demonstration Facility; SUMMERFELT, STEVEN - Freshwater Institute

Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2016
Publication Date: 9/30/2016
Publication URL: http://handle.nal.usda.gov/10113/5569156
Citation: Davidson, J., Summerfelt, R., Barrows, F., Gottsacker, B., Good, C., Fischer, G., Summerfelt, S. 2016. Walleye Sander vitreus performance, water quality, and waste production in replicated recirculation aquaculture systems when feeding a low phosphorus diet without fishmeal versus a traditional fishmeal-based diet. Aquacultural Engineering. 75:1-13.

Interpretive Summary: Walleye are a popular sport and food-fish species in states and provinces bordering the Great Lakes. Walleye are mainly provided as food-fish to US markets by limited capture fisheries, but demonstrate potential for production in land-based recirculation aquaculture systems (RAS). An increased understanding of production metrics for food-sized walleye raised in RAS is needed to facilitate expansion of the walleye industry. The use of sustainable, fishmeal-free diets that limit pollutants while maintaining optimal walleye performance is also required. This research found that a fishmeal-free diet resulted in acceptable walleye growth, feed conversion, and food quality, while reducing phosphorous discharge from RAS. These results add to the body of knowledge available to investors and fish farmers interested in walleye production. Use of this fishmeal-free diet in conjunction with RAS production technology increases the potential for fish farmers to meet local effluent regulations, possibly reduces the capital investment related to waste treatment, and widens the number of prospective sites for walleye aquaculture facilities.

Technical Abstract: Walleye Sander vitreus is a popular sport- and food-fish in areas surrounding the Great Lakes. Walleye are mainly provided as food-fish by limited capture fisheries, but have potential for profitable production to market-size in recirculation aquaculture systems (RAS). Walleye are piscivorous with a supposed requirement for fishmeal in artificial diets, thus little information is available regarding the effects of feeding fishmeal-free diets to walleye. During this study, the health and growth performance of juvenile walleye cultured in RAS were compared between groups fed either a traditional fishmeal-based diet (FM) or a low phosphorous, fishmeal-free (FMF) diet. Water quality and waste production rates resulting from feeding each diet were evaluated. The FM diet contained fishmeal, poultry meal, soybean meal, wheat flour, and blood meal proteins; and the FMF diet used poultry meal, wheat flour, soy protein concentrate, and corn protein concentrate proteins. The only lipid source used in the FM diet was fish oil from menhaden, whereas the FMF diet used menhaden oil and poultry oil. Each diet was formulated with a protein: fat ratio of approximately 42/18. Fish (initial weight 85 g fish-1) were cultured in 6 replicated RAS for 9 months, each operated with 99.9 % water recycle on a flow basis, a mean system hydraulic retention time of 135 days, and a mean feed loading rate of 3.5 kg feed/m3 of daily makeup water. At study's end, mean weights plus or minus standard error of fish fed the FM and FMF diets were 571 plus or minus 26 and 589 plus or minus 15 g, respectively (P greater than 0.05). Cumulative survival for both diet treatments was greater than 98.5 %. Average thermal growth coefficient (TGC), condition factor (CF), and feed conversion ratio (FCR) were similar (P greater than 0.05) for the FM and FMF diets, respectively: TGC was 0.82 plus or minus 0.01 and 0.83 plus or minus 0.02; CF was 1.05 plus or minus 0.02 and 1.03 plus or minus 0.02; and FCR was 1.32 plus or minus 0.02 and 1.27 plus or minus 0.03. Water color index and UV transmittance values (P less than 0.05) indicated slightly clearer water in RAS where the FMF diet was fed. Total nitrogen (TN) was greater (P less than 0.05) in the culture water of RAS associated with the FM diet; however, TN production per unit feed was similar between treatments; 0.031 plus or minus 0.010 kg TN/ kg feed for the FM diet and 0.030 plus or minus 0.009 kg TN/kg feed for the FMF diet. Total phosphorous (TP) concentration in the culture water of RAS associated with the FMF diet was 48 % of that measured for the FM diet; TP produced per unit feed reflected this trend, 0.107 plus or minus 0.003 vs. 0.0049 plus or minus 0.006 kg TP / kg feed for the FM and FMF diets, respectively. Average fillet yield (skin and scales on) of fish harvested at the end of the trial was 47-49 % (P greater than 0.05). Whole-body and fillet proximate composition was similar between treatments; however, gonadosomatic index and the ratio of omega 6: 3 fatty acids was greater (P less than 0.05) for walleye fed the FMF diet. This was the first study of its kind to report comparable walleye growth when feeding a specially formulated diet devoid of fishmeal and while culturing this species in RAS. Reduced phosphorous discharge resulting from feeding this fishmeal-free diet formulation increases the feasibility of meeting stringent effluent requirements and possibly reduces the capital investment required for waste treatment.