Trophic Relations of Lesser-Spotted Catshark (Scyliorhinus canicula) and Blackmouth Catshark (Galeus melastomus)

The feeding habits of Scyliorhinus canicula and Galeus melastomus were investigated by ana-lysing the stomach contents from 6 036 individuals collected on research surveys in the southern region of the Bay of Biscay during the autumns of 1988–2001. These catshark species are the most abundant scyliorhinids on the Cantabrian shelf. Their depth ranges partly overlap, although they occur in different habitats. Both catshark species are opportunistic scavengers, with their main prey being fish and crustaceans. Diets of the two species overlap; they are most similar in individuals <30 cm total length (TL) where euphausiids are important prey, but, for individuals ≥30 cm TL, fish (mainly discarded from trawlers) are important prey. Lesser-spotted catshark are mostly benthic feeders and they feed on a greater diversity of prey than blackmouth catshark, which are more suprabenthic. Re-source partitioning between the two species appears to depend on the better vision of the blackmouth catshark, which feeds more in the water column whereas the better developed olfactory sense of the lesser-spotted catshark is an adaptation to benthic feeding. The broad diets of these catshark species and their consumption of fish discarded from trawlers may make them good indicators of fishing-induced change in the Cantabrian Sea ecosystem