Humpback whales face higher risks of becoming tangled in fishing gear during years when warming ocean temperatures diminish their traditional cold-water habitats, as revealed by recent research findings. The study, conducted off the U.S. West Coast by the National Oceanic and Atmospheric Administration and detailed in the peer-reviewed journal PLOS Climate, emphasized that the reduction in cold-water environments poses a greater threat of entanglement than the sheer increase in humpback numbers.
Cold-water habitats play a vital role for species like humpback whales by fostering abundant marine life, including krill and small fish crucial to the whales’ diet. Geoff Shester, a senior scientist at Oceana, explained that cold water, rising from the ocean depths, undergoes compression due to marine heat waves associated with climate change, limiting the available feeding areas in a process known as habitat compression.
The overlap between these restricted feeding zones and open fishing areas results in heightened interactions between whales and fishing gear, creating a hazardous scenario. This situation can be especially detrimental to humpback whales, as highlighted by Andrew Trites, director of the Marine Mammal Research Unit at the University of British Columbia, who pointed out the severe consequences when humpbacks get ensnared in fishing gear.
Research conducted by NOAA scientists, led by Jarrod Santora, found a significant surge in reported humpback entanglements off the West Coast starting in 2014, with numbers peaking during the 2015-2016 marine heatwave period known as “the blob.” The analysis revealed that entanglements correlated more strongly with diminished cold-water habitats than with population growth, indicating that other factors were at play.
To address this pressing issue, the researchers developed the Habitat Compression Index, a predictive tool that forecasts ocean conditions several months in advance. This index serves as a valuable resource for preemptively identifying high-risk entanglement periods and locations, enabling authorities to implement targeted fisheries closures. Moreover, advancements like ropeless fishing gear offer promising solutions to mitigate entanglement risks and safeguard marine life while allowing sustainable fishing practices to continue.