Growth, survival, and quality of juvenile walleye Stizostedion vitreum as influenced by n−3 HUFA enriched Artemia nauplii

Abstract

We quantified how addition of n−3 highly unsaturated fatty acids (HUFA) to brine shrimp ( Artemia sp.) nauplii influenced growth, survival, osmotic challenge and fatty acid composition of juvenile walleye. Four groups of 6-day-old walleye were fed enriched Artemia. Lipids were altered to provide four treatments: (1) 100% cod liver oil (CLO), (2) 60% CLO/40% n−3 HUFA concentrate, (3) 40% CLO/60% n−3 HUFA concentrate, and (4) 100% n−3 HUFA concentrate. Different enrichments influenced neutral lipids of Artemia, but not their phospholipids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations in Artemia neutral lipids in treatment 4 were doubled compared to treatment 1. Fatty acid composition of walleye body lipids, in both neutral and phospholipid fractions, reflected the changes in EPA and DHA concentrations found in enriched Artemia. After 3 weeks, walleye fed Artemia enriched with a combination of CLO and n−3 HUFA concentrate grew faster than those fed 100% n−3 HUFA enriched Artemia. Walleye fed Artemia nauplii enriched with 100% CLO survived better than all other treatments (25.0±4.5 vs. 11.4–13.1%). Walleye recovery after osmotic challenge was ordered treatment 1 through treatment 4; as n−3 HUFA in Artemia increased, so did susceptibility to this challenge. Furthermore, both survival and vitality of walleye were negatively correlated with the EPA/(arachidonic acid) AA ratio in their whole body phospholipids. The present work extends our knowledge on the effect on n−3 HUFA at higher levels in walleye juveniles diets (12.5% EPA, 5% DHA), and alterations in whole body fatty acids balance. We conclude that high EPA/DHA diet can be responsible for a decreased survival and higher susceptibility to stress in freshwater fish.