Journal Article

Demersal trawling waste as a food source for Western Mediterranean seabirds during the summer

Alejandro Martínez-Abraín, Raquel Maestre and Daniel Oro

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 59, issue 3, pages 529-537
Published in print January 2002 | ISSN: 1054-3139
Published online January 2002 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1006/jmsc.2001.1175
Demersal trawling waste as a food source for Western Mediterranean seabirds during the summer

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We studied the use of demersal trawler discards by scavenging seabirds at one location in the western Mediterranean (Benidorm, SE Spain) from the end of June to the beginning of October 2000. Yellow-legged gull and Cory's shearwater were the most common species in the study area (52.35%, 35.49%) and behind boats (82.4%, 7.07%). Eight other seabird species were observed in much lower numbers following boats (Audouin's gull 2.6%, black-headed gull 2.3%, sandwich 1.5%, black 0.82% and common terns 0.97%, Balearic shearwaters 1.4%, storm-petrel 0.52% and shags 0.36%). Yellow-legged gulls were present behind trawlers in higher numbers than might have been expected by its abundance at sea, whereas Cory's shearwaters were less so.

The discarded fish (“discard”) comprised mainly of sardine (22.4%), flatfish (19.1%) and horse-mackerel (17.3%) and included fish of a small size (median 10.5 cm) in the main. Yellow-legged gull made the largest use of discards, albeit lower than expected by its Presence Index. Average percentage consumption was about 54% of the edible discards, suggesting that yellow-legged gulls were not highly efficient at catching “discard”. The average ratio of fish discarded over fish landed was ca. 65%, although the range was very variable (23–175%). Estimates of the energy requirements of yellow-legged gulls and “energy availability” from the ca. 8 tonnes of discard produced every fishing day, suggest that trawling waste was probably enough to support a local gull population four times larger than that present during the study period. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.

Keywords: discards; energetics; fisheries; food; foraging efficiency; seabirds; trawlers; western Mediterranean

Journal Article.  0 words. 

Subjects: Environmental Science ; Marine and Estuarine Biology

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