High trophic level consumers such as demersal fish influence the trophic structure of marine benthic communities. Owing to their high mobility, consumers could act as integrators by connecting food webs. But do fish species in the North Sea link food webs of benthic communities or do they feed habitat dependent on a local scale? We examined the diet of the dominant benthic fish species (dab, plaice, whiting and grey gurnard) at the North Frisian sublitoral in the German Bight. The study area comprises various habitats with their typical benthic associations. Sediments from fine to coarse sands, gravel and even rocky habitats are present. The diet of fish from two different habitats (fine and coarse sands) was compared by two methods: (a) stomach content analyses to identify distinct prey items as a kind of snapshot and (b) stable isotopes (δ15N) to investigate long-term differences of habitat-dependent diet, i.e. differences in trophic positions. Both methods enable us to estimate inter-specific differences in feeding, i.e. to determine trophic niches of species and to compare intra-specific differences of habitat-dependent diet. Knowledge on trophic interactions of fish based on habitat dependency might therefore provide a key to determine habitats essential for fish feeding, useful for the development of ecological management and strategies for conservation.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > CO2-Coastal diversity - key species and food webs