Linking prey composition of haddock Melanogrammus aeglefinus to benthic prey availability in three different areas of the northern North Sea.

The feeding strategy and prey selection of haddock Melanogrammus aeglefinus related to the benthic infauna in the field were investigated in three different study areas (boxes) in the northern North Sea in 2007. The stomach contents of M. aeglefinus were dominated by invertebrates in all three boxes, mainly echinoderms and polychaetes, similar to the benthic communities in the field. Prey densities in the field significantly determined prey selection and, thus the feeding strategy of M. aeglefinus appeared highly opportunistic. Other prey characteristics, such as the position in the sediment or its palatability, had no significant effect on the selection process although trends were apparent that tubicolous polychaetes of the family spionids, especially Spiophanes kröyeri and Spiophanes bombyx as well as the tentaculate Phoronis spp., were not consumed and potentially avoided due to their ability to withdraw below the feeding depths or due to chemical deterrents. High abundances of echinoderm species with hard calcareous shells in the M. aeglefinus stomachs, such as the ophiurid Ophiocten affinis and the echinoid Echinocyamus pusillus, indicated their use as grinding elements. A gradual shift from benthos to fish feeding with increasing M. aeglefinus size was not found.