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Entanglements of humpback whales in fish farms rare, and naivety could be to blame

The first of humpback whale entanglements in B.C. aquaculture facilities in PLOS One found eight over 13 years, with the curiosity of young whales a potential contributing factor.

Entanglements are one of several threats to humpbacks. The eight occurred from 2008 to 2021 at seven fish farms, with five animals successfully released and three deaths. The entanglements accounted for less than 6% of all entanglements in B.C. Approximately 7,000 animals return to B.C. waters annually.

Most whales became entangled between the predator and containment nets on fish farms. In five cases, experienced responders were called to lower the predator net, allowing the whales to escape. "This work gives us hope we have strategies and protocols in place to respond to entanglements," said first author Rhea Storlund, a doctoral student in UBC's Institute for the Oceans and Fisheries (IOF).

Contributing factors to entanglement included facility design, anatomy and age: all whales entangled were young. "This could be due to naivety and inexperience, as well as developing new feeding methods compared with adults," said co-author Dr. Stephen Raverty, IOF adjunct professor.

Co-author Dr. Andrew Trites, IOF professor, said those industries including fishing involved in the other 94% of entanglements needed to step up to minimize the harms caused to whales.