Effects of sediment type and food abundance on the vertical distribution of the starfish asterina pectinifera

Abstract

The present study investigated how the vertical distribution of the subtidal starfish Asterina pectinifera (Muller and Troschel) is affected by sediment type and food abundance. During seasonal surveys over 1 yr in Maizuru Bay, Japan Sea, A. pectinifera were abundant in shallow zones (3 to 5 m depth) which were dominated by coarse-grained sediments such as pebbles and oyster shells, while A. pectinifera were scarce in deep zones (7 to 11 m depth) which were dominated by fine-grained muddy sediments. Correspondingly, attractiveness of the coarse sediments to A. pectinifera was suggested by the following 3 results. First, for each depth, A. pectinifera occurred more frequently on the coarse sediments than on the fine sediments. Second, marked A. pectinifera translocated into the deep zones returned to the shallow zones, while those released into the shallow zones remained. Third, A. pectinifera translocated with the coarse sediments into the deep zones remained, while those translocated without the coarse sediments rapidly dispersed. Such attractiveness of the coarse sediments appeared to arise from not microhabitat but food in these sediments, because A. pectinifera, translocated with manipulative coarse sediments into the deep zones, did not differ in number between the sediments with or without microhabitats, but preferred sediments with food retained to those with food removed. In conclusion, the vertical distribution of A. pectinifera is affected by that of the coarse sediments, because the coarse sediments provide abundant food.