By-catch of common minke whales (Balaenoptera acutorostrata) in Norwegian demersal trawl and longline fisheries, 2011–2020

André Moan; Arne Bjørge

doi:10.7557/3.8083

Authors

André Moan Institute of Marine Research, Dept of Marine Mammals, Tromsø, Norway https://orcid.org/0000-0001-9506-2949
Arne Bjørge Institute of Marine Research, Dept of Marine Mammals, Oslo, Norway https://orcid.org/0000-0002-2626-2071

DOI:

https://doi.org/10.7557/3.8083

Keywords:

Common minke whale, Balaenoptera acutorostrata, by-catch, by-catch estimates, cetacean, PBR

Abstract

The Norwegian High Seas Reference Fleet (HSRF) reported one minke whale (Balaenoptera acutorostrata) by-caught in demersal trawl fisheries and one in a longline in the period 2011–2020. The HSRF comprises 25–30 concurrent fishing vessels larger than 15 m total length, contracted by the Institute of Marine Research to provide detailed reports on fishing effort, catch, and by-catch. The HSRF is designed to be as representative as possible for large fishing vessels in all of Norway. By-catch per effort for demersal trawl and longline fisheries was calculated based on data from the HSRF and extrapolated using effort data from the corresponding non-observed fleet (vessels ≥ 15 m) to obtain fleet-wide total by-catch estimates. The total by-catch in demersal trawl and longline fisheries was 57 whales for the 10-year period (95% CI: 0–157). No by-catch of minke whales was observed in other gear types (purse seine, Danish seine, and gillnets), but information from various sources indicates that there is an unknown amount of cryptic minke whale by-catch in other gears that we cannot currently quantify. Pot and creel fisheries, for example, were not covered by the HSRF, and there is a need to quantify by-catch in these fisheries. Notwithstanding undocumented sources of by-catch, the results show that even if 100% of minke whale by-catches are fatal, documented by-catch in Norwegian fisheries is only about 0.5% of the PBR and can be considered negligible from a sustainability perspective. Even so, minke whale by-catch is still a serious animal welfare issue.

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