An experimental analysis of the importance of body-size in the seastar-mussel predator-prey relationship

Laboratory feedings experiments were conducted to elucidate size-relationsh ips in the seastar-mussel (Asterias rubens-Mytilus edulis) predator-prey in teraction. This is one of the most well-known predator-prey relationships i n marine benthic ecology and the dependence of seastar feeding rates and pr ey size selection are crucial for modelling. Moreover, the hypothesis shoul d be rested that large individuals of M. edulis enjoy a size-refuge from se astar predation in the Baltic sea. Ingestion rates showed an allometric rel ationship to seastar size. They increased slightly more than cubically (b = 3.62) with the linear size of the seastars and slightly more than linearly (b = 1.27) with the body mass of the seastars. Somatic growth rates were l inearly related to ingestion rates. Lager seastars tended to eat larger mus sels. This relationship was significant for the largest size of mussels eat en and for the mean size of mussels eaten, but not for the minimal size. Si ze selection of seastars did nor depend on the spatial arrangement of musse l sizes relative to the initial position of the seastars in the aquarium. M ussels of > 48 mm in length are safe from predation by the largest seastars found in the western Baltic sea. (C) Elsevier, Paris.