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Estimates of humpback and minke whale entanglements in Scotland
Ellie MacLennan, Russell Leaper, Andrew Brownlow, Susannah Calderan, Dan Jarvis, Lauren Hartny-Mills and Conor Ryan
International Whaling Commission
Entanglement in static fishing gear has been identified as the largest anthropogenic cause of mortality in minke (Balaenoptera acutorostrata) and humpback whales (Megaptera novaeangliae) in Scottish waters, and is of increasing concern from both a welfare and conservation perspective. However a thorough understanding of the scale and impacts of these incidents is lacking. To address this, data from a number of sources including strandings, live disentanglement reports and interviews with inshore creel fishermen were gathered to provide estimates of entanglements, using a capture-recapture type approach and extrapolation of interview data. The findings suggest that the Scottish creel fishery may be responsible for considerably more whale bycatch than previously thought, with estimates of around five humpback whales and 30 minke whales becoming entangled each year. Entanglements occurring in Scottish waters could potentially impact small populations of humpback whales in the NE Atlantic. For the west coast of Scotland, the estimated fatal entanglement rate of minke whales is 2.2% of the estimated abundance from the SCANSIII survey suggesting a risk of localised depletion. Scottish fishermen have exhibited willingness to engage in mitigation strategies and research, with suggestions such as the introduction of leaded line to the sector. Some have also been participating in informal trials of ropeless technologies. To date these trials have been successful and we recommend that continued support for such mitigations, which could greatly reduce entanglement risk, be considered with urgency.