Food of flathead sole Hippoglossoides elassodon in the eastern Bering Sea

Abstract

The food habits of the flathead sole (Hippoglossoides elassodon) in the eastern Bering Sea were investigated. Our analysis of 4,406 flathead sole stomachs containing food showed that the diet was composed primarily of organisms living on the bottom (epibenthic) and pelagic organisms in close association with the bottom (nektobenthic). Feeding shifted from a crustacean-based diet to an ophiuroid-based diet with increasing fish size. Flathead sole less than 30 cm total length (TL) consumed mainly mysids, gammarid amphipods, and decapod shrimps, whereas flathead sole larger than 30 cm total length (TL) consumed mainly ophiuroids, walleye pollock, and decapod shrimps. Diet composition varied with changes in bottom depth. Feeding in shallow waters (less than or equal to 50 m) was almost exclusively on small crustaceans and fish, but shifted to ophiuroids with increasing bottom depth for both size groups. The diet of flathead sole is indicative of a generalist feeding strategy. Dietary diversity ranged from moderately low to high as measured by Shannon-Weaver and Simpson's diversity indices, and the diet appears to be influenced mainly by prey availability and abundance. Lower diversity values for flathead sole larger than 30 cm TL suggest that feeding becomes more selective as fish grow. Competition with other flatfish species in the eastern Bering Sea does not appear to be a major factor influencing the diet of flathead sole.


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