Feeding ecology of the velvet swimming crab Necora puber in mussel raft areas of the Ría de Arousa (Galicia, NW Spain)

Abstract

The feeding ecology of the velvet swimming crab Necora puber (Decapoda: Portunidae) in 3 mussel raft culture areas of the Ria de Arousa (Galicia. NW Spain) was studied through the analysis of stomach contents. The dominant prey was Pisidia longicornis (50 to 81 % of the diet in the different areas), a small epifaunal anomuran crab that inhabits culture ropes. Other important food components were brachyuran crabs, the mussel Mytilus galloprovincial~s and other bivalves, gastropods, egg cases of the gastropod Nassa spp., the echinoid Psammechinus mliarjs and fishes. Plants (both eelgrass and seaweeds), sponges and polychaetes const~tuted secondary prey, with low quantitative mportance. Habitat was the most ~rnportant factor in diet variability within the ria, related to the spatial differences in abundance and structure of the benthic and raft epifaunal communities. Also, important differences were observed between the diet in soft bottom areas of the Ria d e Arousa and rocky zones in other geographical areas, where the importance of seaweeds was higher. The diet of N. puber was dominated by raft epifauna and mussels, and also by the megabenthos. Macroinfauna and plants showed little quantitative importance. For the epifaunal prey, P. longicornis was selected positively and amphipods negatively; in the case of the infauna, bivalves and ophuroids were selected positively, and polychaetes negatively. Diet variability related to Me history was due mainly to ontogenetic changes. Fishes, brachyurans, mussels, echinoids and sponges increased their contribution to the diet with growth, but P. longicornis, egg cases of Nassa spp., and the holothurian Aslia lefevrei presented the opposite pattern. The relationship between body size and gut fullness presented a negative allometry, but absolute food consumption increased with size Food consumption variability was linked mainly to intermoult stage and season. Dunng the immediate premoult and postmoult, there was no food ingestion; however, gut fullness was higher in the recent postmoult compared to intermoult animals. Seasonal changes were due to higher food consumption in autumn and winter.

Influence of mussel aquaculture on the distribution of vagile benthic macrofauna in îles de la Madeleine, eastern Canada

“…compared to adjacent soft bottom habitats). The existence of a trophic mechanism is also supported by the studies by Freire et al (1990) and Freire & González-Gurriarán (1995), who showed that crabs in mussel culture areas increase the proportion of mussels in their diets relative to that of crabs in areas outside of mussel farms. A trophic mechanism also supports observations of variation in the distribution of macrofauna within farms.…”

“…Mussels are among the main prey items of rock crabs in coastal areas and in the general study area (Drummond-Davis et al 1982, Hudon & Lamarche 1989. Romero et al (1982) observed a greater abundance of various crab species in areas with mussel rafts than in areas without them in the Ría de Arousa, Spain, and stomach content analysis of crabs in the same region showed crab diets shift to include more mussels in farm areas (Freire et al 1990, Freire & González-Gurriarán 1995. Likewise, mussels are the preferred prey of many starfish (Penney & Griffiths 1984, Gaymer et al 2001, and aggregations of starfish have often been noted with fallen mussels at mussel farm sites (Olaso Toca 1982, D'Amours et al 2008, Wilding & Nickell 2013, suggesting that they are attracted to mussel farms for the abundant prey they offer.…”

Feeding ecology of <i>Parapenaeus longirostris</i> (Lucas, 1846) (Decapoda: Penaeidae) from the Ionian Sea (Central and Eastern Mediterranean Sea)

“…For example, the crab Necora puber shows increased preference for fish and decapods with growth and reduces the predation on non-decapod crustaceans and plants (Freire and González-Gurriarán, 1995). In general, an increase in the predator size means that the prey size will increase (Dall et al, 1990).…”

Local enhancement of epibenthic macrofauna by aquaculture activities

“…González-Gurriarán (1986) and Freire & González-Gurriarán (1995) showed that mussel rafts constituted an important source of food for crabs. Likewise, Romero et al (1982) showed that increased crab density was associated with the abundance of food from sessile epifaunal species and biodeposition.…”