Evaluation of commercial and experimental grower diets for use in intensive burbot (Lota lota maculosa) culture

Burbot (Lota lota maculosa) are the only true freshwater gadiforms (cod-like fish) and are a promising new species for cold water aquaculture. This "freshwater cod" produces a delicate white flesh fillet, the liver and roe are considered delicacies, and the skin can be manufactured into leather. Furthermore, burbot grow-out requires similar water quality parameters as trout production, and burbot have been found to be relatively refractory to most primary salmonid pathogens. Burbot could be reared at existing trout production facilities and represent a means of diversifying production in already established cold water aquaculture operations. For commercial burbot culture to succeed, optimal diet selection for grow-out must be determined. To address this, two feeding trials were conducted to evaluate the effect of different dietary formulations on the growth of juvenile and subadult burbot. Four dietary treatments at fixed rations were evaluated, Europa (commercial), Oncor (commercial), a formulated marine-like reference diet (Burbot 1; B1), and a formulated trout-like reference diet (Burbot 2; B2). Juvenile growth results indicated a difference in relative growth (RG; P < .001) and biomass gain (BG; P < .001) among the marine blend dietary treatments, with the fish fed B1 and Europa showing better growth than the Oncor and B2 diets in these cases. This is indicative of a preference for marine-type diets during the juvenile life stage of burbot. Growth results also indicate a difference in protein efficiency ratio (PER; P = .008) among the diets, with the fish fed Europa exhibiting the lowest protein utilization rate. Subadult growth results indicate no differences in RG (P = .771), SGR (P = .804), BG (P = .727) for fish fed any of the diets. Thus, it appears that the subadult burbot grow and perform equally well on trout-like formulations at this life stage. While additional studies are needed, results from this work are important and indicate general dietary preference of burbot at juvenile and grow-out stages. Such information can be used to guide feed related decisions for current or future producers interested in commercial burbot production.