At-sea distribution and diet of an endangered top predator: relationship between white-chinned petrels and commercial longline fisheries

• Published in: Endangered Species Research
• Main Authors: Delord, K, Cotte, C, Peron, C, Marteau, C, Pruvost, P, Gasco, N, Duhamel, G, Cherel, Y, Weimerskirch, H
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter-Research 2010
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Antarctic; Indian; Antarc*
• Online Access: https://doi.org/10.3354/esr00309; http://ecite.utas.edu.au/92767

Incidental seabird mortality associated with longline commercial fishing is a worldwideconservation concern. To develop conservation strategies, it is essential to estimate the likelihood ofseabird bycatch and the degree of overlap between birds foraging grounds and commercial fishingareas. We tracked 21 adult white-chinned petrels Procellaria aequinoctialis breeding on KerguelenIsland, southern Indian Ocean, during their breeding period in 2006 and in 2008. At-sea foraging distributionof white-chinned petrels was mainly confined to Antarctic waters. Commercial longlinefisheries targeting toothfish were operating in both the French Exclusive Economic Zone and in otherCommission for the Conservation of Antarctic Marine Living Resources areas during the study. Weanalysed concurrent data on the positions of both birds and vessels to estimate overlap. Static analysisusing indices (home-range and utilization distribution overlap) revealed that, at a large scale, spatialand temporal overlap occurred, but varied among areas and with breeding stage. Dynamic analysis(detection of operating vessels respective to bird locations within a time/space window) revealedlittle overlap at a small scale. Our study revealed a mismatch between large- and small-scale overlapestimates, suggesting that birds and vessels occupy the same overall zone with infrequent co-occurrence(19% of birds in the vicinity of vessels). This result was confirmed by the relatively low occurrenceof fishery-related items (4 to 22%) in chick food samples. However, given the large size ofseabird populations, overall, large numbers of birds overlap with vessels, and management authoritiesshould maintain and promote the implementation of strict mitigation measures to further reducebycatch.