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  • 1
    facet.materialart.
    Unknown
    Oxford Univ. Press
    In:  ICES Journal of Marine Science (57). pp. 531-547.
    Publication Date: 2019-09-23
    Description: Birds are the most conspicuous, wide-ranging, and easily studied organisms in the marine environment. They can be both predators and scavengers, and they can be harmed by and can benefit from fishing activities. The effects of fishing on birds may be direct or indirect. Most direct effects involve killing by fishing gear, although on a lesser scale some fishing activities also disturb birds. Net fisheries and hook fisheries have both had serious negative effects at the population level. Currently, a major negative impact comes from the by-catch of albatrosses and petrels in long-lines in the North Pacific and in the Southern Ocean. High seas drift nets have had, prior to the banning of their use, a considerable impact on seabirds in the northern Pacific, as have gillnets in south-west Greenland, eastern Canada, and elsewhere. Indirect effects mostly work through the alteration in food supplies. Many activities increase the food supply by providing large quantities of discarded fish and wastes, particularly those from large, demersal species that are inaccessible to seabirds, from fishing vessels to scavengers. Also, fishing has changed the structure of marine communities. Fishing activities have led to depletion of some fish species fed upon by seabirds, but may also lead to an increase in small fish prey by reducing numbers of larger fish that may compete with birds. Both direct and indirect effects are likely to have operated at the global population level on some species. Proving the scale of fisheries effects can be difficult because of confounding and interacting combinations with other anthropogenic effects (pollution, hunting, disturbance) and oceanographic factors. Effects of aquaculture have not been included in the review
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2019-01-21
    Description: While Lesser Black-backed Gull Larus graellsii numbers increase substantially at the German North Sea coast since the late 1980s, Herring Gull Larus argentatus numbers have been roughly stable since the mid-1980s. In order to investigate whether a different ecology might explain the current trends, we studied diet, colony attendance, reproductive output and aggressive behaviour in a mixed-colony on Amrum, southeastern North Sea, in 1994 and 1995. During incubation Lesser Black-backed Gulls fed mainly upon crustaceans and molluscs which were taken from the intertidal zone. During chick-rearing, they took mainly crustaceans and fish which were gathered mostly as trawler discards. The main food of Herring Gulls throughout the reproductive season were molluscs and crustaceans which were obtained from the intertidal zone. Numbers of Lesser Black-backed Gulls in the colony mainly varied with season and time of day, those of Herring Gulls with tide and season. Numbers of Herring Gulls commuting to the open sea roughly equalled those commuting to the Wadden Sea. Lesser Black-backed Gulls generally flew to the open sea but hardly towards the Wadden Sea. Nest attendance was significantly higher in Lesser Black-backed Gulls than in Herring Gulls during the chick-rearing period. Hatching success and fledging success tended to be higher in Lesser Black-backed Gulls. Lesser Black-backed Gulls won interspecific aggressive interactions significantly more often than Herring Gulls in the chick-rearing period. Our study indicates that Lesser Black-backed Gulls currently enjoy a few ecological advantages compared with Herring Gulls, particularly because they feed on food of apparently higher quality. We conclude that Lesser Black-backed Gulls have filled an empty niche rather than have out-competed Herring Gulls during the past decades
    Type: Article , PeerReviewed
    Format: text
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