Behaviour of Sacculinized Shore Crabs (Carcinus maenas Pennant)

Abstract

For some years investigations on the ecology of the common shore crab, Carcinus maenas, have been carried out in inshore Danish waters (the Isefjord area, Zealand) and among other things the migrations of the species were studied. In contrast to the observations from British waters of Williamson¹ and others, it was observed that during the breeding season—which in the Isefjord comprises only May and June—the berried female crabs leave the littoral areas and hide in the more saline and deeper water (maximum depth 8–10 metres) until the larvæ are hatched. After this period they return to moult and copulate with the male crabs which stay all summer in shallow water (0–1.5 metres). The annual mean salinity of the Isefjord is 19.4 per mille.