A whale forecast for fishermen

The opening of California’s commercial crab season, which normally begins in November, has been postponed again to protect humpback whales that forage for krill and anchovies along the coast.

This region of the Pacific Ocean is in the grip of a heat wave at sea since May. ‘The Blob’, as this mass of warm water has become known, squeezes out cooler water favored by whales and their prey, close to shore where fishermen 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 increase the risk of whale entanglement. This lead time could allow state regulators, fishermen and other businesses that rely on the fishery — as well as Californians hoping for a Dungeness crab holiday meal — to plan ahead for potential fishing restrictions.

“It actually just helps provide a lot more information and reduces some of the uncertainty about the future,” said Steph Brodie, lead author of the study published Tuesday. in the journal Nature Communications. Dr. Brodie is currently a research scientist at Australia’s National Science Agency, but conducted this research while working at the University of California, Santa Cruz and the National Oceanographic and Atmospheric Administration.

The tool analyzed in the new study, called the Habitat Compression Index, works by feeding measurements of sea surface temperatures into an equation that estimates the likelihood of whale habitat shrinking closer to shore. Previously, the index only analyzed recent conditions based on data from the previous month.

But the sea surface temperature itself can be accurately predicted months in advance. According to the new study, the Habitat Compression Index can use these temperature predictions to predict the locations of humpback whales up to 11.5 months into the future. The index was most accurate for winter and spring forecasts.

The scientists also studied hawksbill turtles, which visit the Southern California coast during unusually warm years and sometimes become entangled in swordfish gillnets, and found that they could similarly predict the turtles’ movements months in advance.

California isn’t the only place where scientists can make animal predictions. Dr. Brodie and her colleagues are on a mission to extend advances in satellite observations, physical oceanography and climate science to the domains of ecology and natural resource management worldwide. They call this emerging field “ecological forecasting.”

“One of the exciting things about this research is that it is easy to replicate elsewhere,” said Jarrod Santora, an ecosystem scientist at NOAA and another author of the study. “It’s not really difficult math. Sea surface temperature is available everywhere.”

Ecological predictions could help New England and maritime Canada, where critically endangered whales also become entangled in fishing gear. It is estimated that only about 350 individual whales remain.

The outlook is much brighter for humpback whales, whose populations have recovered in recent decades since the end of commercial whaling. Every year from early spring to late fall, thousands of humpback whales congregate in Northern California and Oregon. They come from balmy winter farms in Mexico and Central America and travel north to find food.

These whales are increasingly sharing territory with California’s fleet of about 400 commercial crab boats, which normally cruise the coast from mid-November to mid-July. California fisheries landed about 21 million pounds of crabs last year, worth just under $55 million, according to NOAA officials.

Regulators and fishermen agree that the new forecast research could help them walk the tightrope between protecting whales and protecting local livelihoods.

“My personal opinion is that this is very, very helpful,” said Richard Ogg, captain of a commercial fishing boat in Bodega Bay.

Mr Ogg describes himself as a keen conservationist who does not want whales to be harmed. Fishermen have a strong incentive to protect the natural environment, he said, because that’s where they make their living. The challenge is to adapt to changing conditions and fishing regulations at short notice, especially for smaller business owners and their crews.

“One of the biggest problems we have is unpredictability,” Mr Ogg said. “We live from week to week.”

2014-2016 were particularly warm, bad years. In 2016, a record 19 humpback whales were found entangled in crab gear off the coast of California. Since then, the state has initiated a special management program that adjusts the crab season to environmental conditions, and the number of whale entanglements has been reduced to about three to four per year.

Although scientists have shown that the Habitat Compression Index can now predict months in advance, state officials would likely wait to see conditions in real time before making crab fishing decisions, said Ryan Bartling, an environmental scientist with the California Department of Fish and Wildlife. But the Dungeness Crab Fishing Gear Working Group, which includes both Mr. Ogg and Dr. Santora, meets with officials monthly and the forecasts can inform their discussions and planning throughout the year, Mr. Bartling said.

The study also analyzed a similar tool for loggerhead sea turtles, created by co-author Heather Welch. It was more accurate in forecasting than the whale instrument, but it was only applied to the summer months.

In 2022, Congress passed federal legislation to phase out floating gill nets that catch loggerheads. Although the turtle tool is not currently being used for regulations, officials are still using it to inform their decisions and communicate with fishermen, said Amber Rhodes, fisheries policy analyst at NOAA.

As the climate changes, many marine species are on the move. Some may turn away from active fishing, while others – such as humpback whales – may move closer. “A lot of times we don’t know how it’s going to work out,” Ms. Rhodes said. Forecasts that give regulators and the industry time and flexibility will help fisheries adapt and be resilient, she said. “That is the real need in a liquid environment like the ocean.”