© 1997 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
An evaluation of the distribution and scavenging habits of northern fulmars (Fulmarus glacialis) in the North Sea
Netherlands Institute for Sea Research P.O. Box 59, 1790 AB Den Burg, Texel, The Netherlands
Institut für Meereskunde, Düsternbrooker Weg 20 24105 Kiel, Germany
Institut für Vogelforschung "Vogelwarte Helgoland" Inselstation P.O. Box 1220, D-27494 Helgoland, Germany
Correspondence to C. J. Camphuysen: tel: +31222369488; fax: +31222319674; email: camphuys{at}nioz.nl
Northern fulmars (Fulmarus glacialis) are abundant scavengers at fishing vessels in the North Sea. However, despite their abundance and apparent feeding success at (some) fishing vessels, the contribution of discards and offal to their food intake cannot be fully estimated in the absence of less easily gathered data on natural foods. Direct study of fulmar diet has failed to determine the relative importance of discards and offal in the diet. In this paper, the feeding ecology of, and the importance of fishing activities for, fulmars across the whole North Sea is evaluated using results from cruises of fishery research vessels and also observations from a commercial beam trawler. Fulmar and fishery distribution, prey selection and feeding success of scavenging birds, and the relationship of fulmar distribution with hydrographic parameters are the main topics of this study. We found that: (1) fulmars were most abundant in regions of the North Sea where the supply of fishery waste was comparatively low; (2) hydrography predicts fulmar distribution better than fisheries; (3) fulmars at fishing boats obtain discarded offal in proportion to their numerical abundance, but obtain relatively small amounts of discarded roundfish; (4) roundfish are easily robbed from fulmars, and that a marked decline in feeding success in autumn and winter might be attributed to increasing numbers of herring gulls (Larus argentatus) at the trawl; and (5) fewer than 50% of the fulmars in the North Sea can be fully supported by fishery waste. These results indicate that, although fulmars clearly profit from fishery waste, fishing activities are not an important determinant of their distribution on a North Sea scale.
Keywords: competition, consumption, diet, discards, distribution, fisheries, Fulmarus glacialis, hydrography, northern fulmars, North Sea, prey selection