A recent study reveals that humpback whales face a higher risk of getting entangled in fishing gear during years when increasing ocean temperatures lead to a reduction in cold-water habitats. Conducted by the National Oceanic and Atmospheric Administration off the U.S. West Coast and documented in the peer-reviewed journal PLOS Climate, the research indicates that the diminishing cold-water areas pose a greater entanglement threat than the rising humpback population.
Cold-water environments play a crucial role for species like humpback whales as they support abundant marine life such as krill and small fish, key components of the whales’ diet. Geoff Shester, a senior scientist at Oceana, explains that cold water, essential for sustaining marine life, can be displaced by marine heatwaves associated with climate change, resulting in limited feeding areas—a phenomenon known as habitat compression.
The overlap of these restricted feeding zones with fishing areas intensifies the risk of entanglement incidents between whales and fishing gear. This interaction is particularly hazardous for humpbacks, as Andrew Trites, director of the Marine Mammal Research Unit at the University of British Columbia, points out their tendency to become tightly ensnared, leading to severe injuries or death.
The study by NOAA scientists, led by Jarrod Santora, observed a notable increase in humpback entanglements off the West Coast since 2014, with a peak of over 40 incidents during the marine heatwave “the blob” in 2015 and 2016. By analyzing entanglements, population dynamics, and cold-water habitat changes over 25 years, the researchers established a correlation between reduced cold-water areas and higher entanglement rates, suggesting that population growth alone does not account for the surge in entanglements.
To address these challenges, the researchers developed the Habitat Compression Index, a predictive tool that forecasts ocean conditions up to a year in advance. This tool aids in identifying high-risk entanglement periods and locations, enabling authorities to implement targeted fisheries closures. Additionally, advancements like ropeless fishing gear offer a promising solution to mitigate entanglement risks in closed areas.
The proactive use of tools like the Habitat Compression Index and innovative fishing technologies could help safeguard humpback whales and reduce entanglement incidents in the future.