engleski

Habitat structure and predation mode predict community assemblages in the shallow benthos of an Adriatic lagoon

Top-down theories of community organization predict that mobile demersal macrofauna reach maximum abundance and diversity in structurally complex habitat, such as seagrass, which obstructs the vision and movement of predators. This prediction, however, oversimplifies by assuming a fixed predation mode and stable densities of predators and prey. If predators are mobile and can exploit structured habitat as ambush cover, then they can exclude most other macrofauna from structured patches. We assayed predator behavior and predation efficiency in fish communities in seagrass and neighboring bare sediment patches in experimental tanks and in nature in the Novigrad Sea, Croatia. We found (1) large ambush predators predominated in seagrass, and smaller chase-attack predators on bare sediment ; (2) overall fish abundance was fourfold higher on bare sediment than in seagrass ; (3) rates of biting, ingestion, and attacking were greatest in seagrass ; and (4) ambush predators were more successful and aggressive than chase-attack predators. Our results are consistent with the conclusion that seagrass has a higher predation risk due to large, aggressive ambush predators, which have forced most small/juvenile fish out of seagrass and onto neighboring bare sediments.

top-down control; demersal macrofauna; abundance and diversity

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