Predation pressure of subtidal animals on the intertidal boulder benthos community.

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Community structure in the intertidal and subtidal boulder shores : The fauna of intertidal community was more abundant than that of subtidal community. In the intertidal area, grazing mollusca was most dominant group. In the subtidal area, however, echinoderm and crustacea relatively increased, and filter feeder and predator were abundant. Dominant subtidal predators were sister (Itomakihitode, Asterina pectinifera), a small mollusca (Himey ouraku, Ergalatax contractus), some hermit crab and some Xanthidae decap oda crab. Except the seastar and a mollusca, their densities were very low. The main food of the seastar was algae. Therefor, I resulted that invertebrate predators in the subtidal area had little predation pressure on the intertidal community.Invasion of subtidal fish : From the diving observation of fish feeding in the intertidal area, I observed that three species of subtidal fish fed on intertidal benthos : Kasago (Sebastiscus marmoratus) Sasanohabera (Pseudolabrus japonicus), Kusafugu (Takifugu niphobles).Stomach content analysis : Invasion fishes in the intertidal area were caught by a gill net. Stomach contents were observed immediately. Kasago showed a strong preference for crustacean decapoda, however, Sasanohabera preferred mollusca. These two fishes caught in the subtidal area frequently fed intertidal benthos. Therefore, I consider that the intertidal area is an important feeding ground of subtidal fishes.