Individual seabirds show consistent foraging strategies in response to predictable fisheries discards

Patrick, Samantha C and Bearhop, Stuart and Bodey, Thomas W and Grecian, W. James and Hamer, Keith C and Lee, Janette and Votier, Stephen C (2015) Individual seabirds show consistent foraging strategies in response to predictable fisheries discards. Journal of Avian Biology. n/a-n/a. ISSN 09088857

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Abstract

Current fishing extraction methods often generate huge quantities of dead or dying biomass that is returned to the sea in the form of discards. This practice produces a readily available clumped resource for many scavengers such as seabirds, but in the face of declining stocks and via policy change, the amount of discards produced is set to decline in the future. To understand how discards have influenced seabird foraging in the past and how birds may respond to future change requires studies examining consistent individual foraging choices. There is increasing evidence that populations may be made up of generalist or specialist foragers and this is key to the population's ability to adapt to change. Here we test for consistent individual foraging behaviour of northern gannets Morus bassanus in relation to fishing vessels and examine consequences of scavenging behaviour in terms of foraging effort and body condition. Using a combination of bird-borne bio-logging devices (GPS and Time Depth Recorders) with high resolution GPS data acquired through vessel monitoring systems on fishing boats, we examined the overlap between birds and fisheries. We found that during repeat foraging trips in the same breeding season, gannets regularly foraged at fishing boats but there were also clear among individual differences in the extent of fisheries overlap. Furthermore, we show for the first time that these differences represent consistent strategies – individual differences in scavenging were highly repeatable across multiple trips within a period of several weeks. However, despite this finding, we found no differences in foraging effort or body condition between scavengers and non-scavengers. Moreover, scavenging strategy did not appear to influence diving behaviour or vary by sex. Scavenging on discards appears to be a strategy employed consistently by a subsection of the population and future work should examine whether these specialisations persist throughout and between years and what causes these individual differences, exploring possible demographic and fitness consequences in light of global changes to fish stocks and fisheries management.

Item Type: Article
Article Type: Article
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Faculty of Business, Computing and Applied Sciences > School of Natural & Social Sciences
Research Priority Areas: Environmental Dynamics & Governance
Depositing User: Anne Pengelly
Date Deposited: 10 Jul 2015 15:29
Last Modified: 10 Jul 2015 15:29
URI: http://eprints.glos.ac.uk/id/eprint/2433

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