Size-related dietary changes observed in young-of-the-year pumpkinseed (Lepomis gibbosus): stomach contents and fatty acid analyses

Changes in dietary composition and its effects on the fatty acid (FA) composition of young-of-the-year (YOY) pumpkinseed (Lepomis gibbosus) from an artificial reservoir (Mirgenbach--northeastern France) were related to body size as shown by stomach content and FA analyses. Comparisons were made between three size classes of fishes: 25-35 mm total length (TL), 35-45 mm TL and 45-55 mm TL. Diets of the youngest L. gibbosus (TL ≤ 35 mm) consisted mainly of zooplanktonic microcrustaceans and Chironomidae. Ontogenetic development influenced the FA composition of L. gibbosus. Older YOY L. gibbosus showed an increase in proportions of monounsaturated FA proportions and a decrease in polyunsaturated FA and mainly essential FA (particularly docosahexaenoic acid). The low ω3/ω6 ratio and low PUFA content (mainly on DHA) suggested that L. gibbosus would not transfer the benefits of consuming ω3 PUFA up the food web.