Partitioning of food resources among Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass, Zostera marina, bed

Abstract

We carried out dietary analysis on five numerically abundant fishes, Sillago japonica, Ditremma temmincki, Tridentiger trigonocephalus, Hippocampus japonicus and Petroscirtes breviceps in an eelgrass bed in Kwangyang Bay, Korea. Comparisons between species demonstrated that the dietary composition of each fish species was significantly different from that of every other species. Although gammarid amphipods and caprellid amphipods were consumed by all species, their individual contributions to each species' diet varied. Furthermore, polychaetes contributed to the diets of S. japonica and T. trigonocephalusand crab larvae were consumed byD. temmincki. Algae and eelgrass were not consumed by four fish species and made only a minimal contribution to the diet of P. breviceps. The diet of each fish species except H. japonicus underwent size-related changes; smaller fishes consumed gammarid amphipods, mysids and copepods, while larger fishes ate polychaetes, gastropods, isopods and other fishes. Differences in the prey organisms consumed of each individual species could be often related to differences in mouth length and width. S. japonica, D. temmincki, T. trigonocephalus, and P. breviceps underwent also a significant diel changes that could be related to differences in foraging behavior and/or prey availability. Thus, use of vision to detect prey would account for the greater daytime consumption of copepods by S. japonica and of crab larvae by D. temmincki, whereas the nocturnal emergence of gammarid amphipods, polychaetes and isopods from the substrate explained their greater consumption by S. japonica, D. temmincki, T. trigonocephalusand P. breviceps at night. Dietary breadth was greater for species with larger mouth dimensions.