December 11, 2023 — The opening of California’s commercial crab season, which normally starts in November, is delayed once again to protect humpback whales foraging for krill and anchovies along the coast.
This region of the Pacific has been under the grip of a marine heat wave since May. “The Blob,” as this mass of warm water has become known, is squeezing cooler water preferred by whales and their prey close to shore, where fishers set their traps.
This crowding can lead to literal tangles between whales and fishing equipment, endangering the animals’ lives and requiring grueling rescue missions.
In a new study, scientists say they can now use global temperature models, commonly used in climate science, to predict up to a year in advance when hot ocean temperatures will raise the risk of whale entanglements. This lead time could allow state regulators, fishers and other businesses that depend on the fishery — as well as Californians hoping for a Dungeness crab holiday meal — to plan ahead for potential fishing restrictions.
“It really just helps give a lot more information and reduce some of that uncertainty about the future,” said Steph Brodie, lead author of the study published Tuesday in the journal Nature Communications. Brodie is currently a research scientist at Australia’s national science agency but conducted this research while working at the National Oceanographic and Atmospheric Administration and the University of California, Santa Cruz.
The tool analyzed in the new study, called the Habitat Compression Index, works by feeding sea-surface temperature measurements into an equation that estimates the likelihood of whale habitat shrinking closer to shore. Previously, the index analyzed only recent conditions, using data from the previous month.