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Evidence of deep-sea interactions between toothed whales and longlines

journal contribution
posted on 2020-01-01, 00:00 authored by Gaëtan Richard, Julien Bonnel, Paul Tixier, John ArnouldJohn Arnould, Anaïs Janc, Christophe Guinet
Toothed whales (odontocetes) feeding on fish caught on hooks in longline fisheries is a growing issue worldwide. The substantial impacts that this behaviour, called depredation, can have on the fishing economy, fish stocks and odontocetes populations, raise a critical need for mitigation solutions to be developed. However, information on when, where and how odontocete depredation occurs underwater is still limited, especially in demersal longline fisheries (fishing gear set on the seafloor). In the present study, we investigated depredation by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) on demersal longlines in the French Patagonian toothfish fishery (Southern Ocean). Using a combination of animal-borne behavioural and longline-attached data loggers, we demonstrated that both species are able to depredate longlines on the seafloor. This study, therefore, suggests that odontocetes whales-longline interaction events at depth may be unrecorded when assessing depredation rates from surface observations during hauling phases only. This result has implications for the management of fisheries facing similar depredation issues as underestimated depredation rates may result in unaccounted fish mortality in fish-stock assessments. Therefore, while further research should be conducted to assess the extent of deep-sea whale-longline interaction events during soaking, the evidence that depredation can occur at any time during the whole fishing process as brought out by this study should be considered in future developments of mitigation solutions to the issue.

History

Journal

Ambio

Volume

49

Issue

1

Pagination

173 - 186

Publisher

Springer

Location

New York, N.Y.

eISSN

1654-7209

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2019, Royal Swedish Academy of Sciences