The Ecology of Lough Ine: VIII. Mussels and Their Predators

Abstract

Mussels (Mytilus edulis and M. galloprincialis.) are abundant intertidally in the Lough Ine area on the open coast and on steep rock faces in ex-tremely sheltered parts of the lough. Small transplanted mussels disappeared except on the open coast. Large transplanted mussels survived in extreme shelter but not elsewhere in the lough. Mussels strewn intertidally and in the shallow sublittoral in the lough were attacked at night by the crabs Carcinus maenas and Portunus puber, and many were destroyed within a few days. Carcinus attacks small mussels, but does not molest seriously large mussels found in extreme shelter. Portunus puber destroys large and small mussels, but is scarce in extreme shelter. Clumps of large mussels placed sub-littorally in extreme shelter were destroyed gradually by the starfish, Marthasterias glacialis. In the Lough Ine area Nucella lapillus is abundant on the open coast but absent from the Mytilus belt in extreme shelter. On transfer to the lough, many Nucella disappeared rapidly, and the remainder moved up to the Fucus spiralis and Pelvetia zones, or higher, where many dried up or became swollen with rain water. Mussels are remarkably tolerant of extreme conditions of inanimate environment. They are probably controlled at Lough Ine by interacting predators which are themselves more sensitive to various physical and chemical conditions, such as wave action and stagnation or low salinity. Predators other than those discussed here, acting on the younger stages, may well be important in this control.