FEEDING ECOLOGY OF THE VELVET SWIMMING CRAB NECORA PUBER IN MUSSEL RAFT AREAS OF THE RIA DE AROUSA (GALICIA, NW SPAIN)

The feeding ecology of the velvet swimming crab Necora puber (Decapoda : Portunidae) in 3 mussel raft culture areas of the Ria de Arousa (Gal icia, NW Spain) was studied through the analysis of stomach contents. The dominant prey was Pisidia longicornis (50 to 81% of the diet in th e different areas), a small epifaunal anomuran crab that inhabits cult ure ropes. Other important food components were brachyuran crabs, the mussel Mytilus galloprovincialis and other bivalves, gastropods, egg c ases of the gastropod Nassa spp., the echinoid Psammechinus miliaris a nd fishes. Plants (both eelgrass and seaweeds), sponges and polychaete s constituted secondary prey, with low quantitative importance, Habita t was the most important factor in diet variability within the na, rel ated to the spatial differences in abundance and structure of the bent hic and raft epifaunal communities, Also, important differences were o bserved between the diet in soft bottom areas of the Ria de Arousa and rocky zones in other geographical areas, where the importance of seaw eeds was higher. The diet of N, puber was dominated by raft epifauna a nd mussels, and also by the megabenthos. Macroinfauna and plants showe d little quantitative importance. For the epifaunal prey, P. longicorn is was selected positively and amphipods negatively; in the case of th e infauna, bivalves and ophiuroids were selected positively, and polyc haetes negatively. Diet variability related to life history was due ma inly to ontogenetic changes. Fishes, brachyurans, mussels, echinoids a nd sponges increased their contribution to the diet with growth, but P . longicornis, egg cases of Nassa spp., and the holothurian AsLia lefe vrei presented the opposite pattern. The relationship between body siz e and gut fullness presented a negative allometry, but absolute food c onsumption increased with size. Food consumption variability was Linke d mainly to intermoult stage and season. During the immediate premoult and postmoult, there was no food ingestion; however, gut fullness was higher in the recent postmoult compared to intermoult animals. Season al changes were due to higher food consumption in autumn and winter.