Over the last century the fish community of the Dutch coastal North Sea zone has lost most its shark and skate species.
Whether their disappearance has changed the trophic structure of these shallow waters has not been properly investigated. In
this study historical dietary data of sharks and skates, being in the past (near)-residents, juvenile marine migrants and marine
seasonal visitors of the Dutch coastal North Sea zone were analyzed for the period 1946–1954. Near-resident and juvenile
marine migrant species were demersal while all marine seasonal visitors species were pelagic. Based on stomach content
composition, the trophic position of four of the various shark and skate species could be reconstructed. The (near)-resident
species, the lesser spotted dogfish, the marine juvenile migrant, the starry smooth hound, and the benthopelagic marine
seasonal visitor, the thornback ray, had a benthic/demersal diet (polychaetes, molluscs and crustaceans), while the pelagic
marine seasonal visitor, the tope shark, fed dominantly on cephalopods and fishes. Diet overlap occurred for fish (tope shark
and lesser spotted dogfish), for hermit crabs (lesser spotted dogfish and starry smooth hound) and for shrimps (thornback
ray and starry smooth hound). Trophic position ranged from 3.2 for thornback ray preying exclusively on crustaceans to 4.6
for the tope shark consuming higher trophic prey (crustaceans and fish). The analysis indicates that most of the shark and
skate species were generalist predators. The calculated trophic positions of shark and skate species indicate that those species
were not necessarily at the top of the marine ecosystem food web, but they might have been the top predators of their
particular ecological assemblage.
