Food habits of salt marsh fishes in Lake Hinuma, Ibaraki Prefecture, central Japan

Abstract

To determine the food habits of salt marsh fishes, the gut contents of 28 species, caught from a salt marsh in Lake Hinuma, Ibaraki Prefecture, central Japan, were investigated. Ontogenetic changes in diet were apparent in six species, including several of commercial importance (e.g., Acanthopagrus schlegelii and Hypomesus nipponensis). Smaller juveniles of such species fed mostly on planktonic copepods, with other prey items, including mysids, gammaridean amphipods and chironomid larvae, forming greater proportions in the diet of larger individuals. A cluster analysis based on dietary overlaps indicated that the salt marsh fish assemblage consisted of seven feeding guilds (small benthic and epiphytic crustacean, zooplankton, aquatic insect, polychaete, plant, terrestrial insect and detritus feeders). Among these, the first two guilds were the most abundantly represented in terms of species number, suggesting that small benthic and epiphytic crustaceans (e.g., mysids and gammaridean amphipods) and zooplankton (e.g., calanoid and cyclopoid copepods) were important food resources for the fish assemblage at the study site.