K.S. Whalen, J.A. Brown, C.C. Parrish, S. Lall, S.J. Goddard
Abstract:
In order to develop a specific diet for marine fish in Newfoundland, the effect of n-3 highly unsaturated fatty acids (HUFA) on the growth of juvenile yellowtail flounder (Pleuronectes ferrugineus) was studied. It has been suggested that cold-water fish require more n-3 HUFA than other species to maintain membrane fluidity. We examined this by feeding fish standard ICES diets containing varying levels of n-3 HUFA ranging between 0.4 and 2.5% and comparing performance with a commercial diet, Biokyowa. Juvenile fish (0+) weighing 1.92+/-0.50 g were fed for 12 weeks in triplicate treatments. Experimental diets and fish liver and muscle were analysed for proximate, lipid and fatty acid composition. Although no mortalities were observed, fish fed the lower n-3 HUFA levels showed significantly lower growth than the Biokyowa and 2.5% HUFA diet. Significant trends were also found in the biochemical compositions of the treatments. Fish fed the 0.4% n-3 HUFA diet had the highest levels of lipid in the liver and the lowest levels in the muscle; however hepatosomatic indices showed no significant differences between treatments. Triacylglycerol levels were highest in the livers and lowest in the muscle of the fish fed the diet lowest in n-3 HUFA and lipid transport was thought to be impaired in these fish, indicating an essential fatty acid deficiency. Fatty acid composition in both liver and muscle was affected by diet. Fish fed the 0.4% diet preferentially conserved the n-3 HUFA in the polar portion of lipid. Results suggest that in this age group, the requirement for essential fatty acids of juvenile yellowtail flounder is approximately 2.5% n-3 HUFA on a dry weight basis.
(Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NF A1C 5S7, Canada)
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