Quick Take:

A study of the 2014 marine heat wave suggests that fishermen who turn to other species will fare better in future climate disruptions.

California’s Dungeness crab fishermen have had a rough year. Poor meat quality, endangered whales migrating too close to shore and price disputes with wholesalers kept crab pots on boats for nearly two months. The delays left families without their cherished holiday centerpiece and fisherman without the funds that normally pay their bills the rest of the year.

But as rising ocean temperatures threaten to make fishery closures routine, it will be even harder to count on crab for holiday meals—or livelihoods. Over the past decade, warming sea waters have produced harmful algal blooms that contaminate crab meat with domoic acid, a neurotoxin that can cause seizures, memory loss and other serious symptoms and has been blamed for poisoning and stranding scores of sea lions in California every year. State officials delayed three out of the last six crab seasons to protect public health after an unprecedented multiyear marine heat wave, dubbed “the blob,” hit the north Pacific Ocean in 2013.

The blob precipitated a series of extraordinary events: it caused a massive harmful algal bloom that led to record-breaking domoic acid concentrations, which in turn caused first-of-its-kind closures of the West Coast’s most valuable fishery, from southern California to Washington state. But in doing so, it also set up a natural experiment that researchers harnessed to reveal strategies that could help food-producing communities recover from climate-driven disturbances.

Flexibility, scientists reported in the study, published last month in the Proceedings of the National Academy of Sciences, or PNAS, was key to adapting to a disastrous heat wave.

Marine heat waves have already become 20 times more frequent under climate change, and scientists expect harmful algal blooms to become more common on the West Coast. To identify factors that might help fisheries adapt to this new reality, researchers from the University of Washington, Oregon State University and the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service analyzed a decade’s worth of crab “landings,” or catches, for seven important crab fishing ports in California.

The researchers looked for patterns across fishing networks to see how crab fishermen responded to the closures. They were particularly interested in identifying factors that made communities more adaptable to disruptions, said coauthor Mary Fisher, a doctoral student at the University of Washington.

Flexibility is important

The 2015-2016 closures were economically devastating for communities that revolve around harvesting and processing crab. As colonies of algae proliferated out of control, Oregon and Washington crab fishermen waited about a month to set out. But California fishers missed out on most of the season, losing half of their average catch and ultimately qualifying for more than $25 million in federal disaster relief.

Some fishermen had reported in surveys that they shifted to other species to offset financial losses, but Fisher and her colleagues wanted to capture a global picture of responses. Toward that end, they analyzed more than 286,000 landing records of fishing trips for more than 2,500 crab boats. They found that fishermen responded in one of three ways: they switched to other species, moved to other locations (to catch other species or crab in areas where delays had been lifted) or stopped fishing.

Most crab boats stopped altogether, a clear indication of the climate shock’s disruptive effects. “Vessels that were able to stay on the water switched to other species or locations, suggesting that flexibility in what and where you can fish are important coping strategies,” Fisher said.

Most crab boats that kept fishing had access to other fisheries, including sablefish, lingcod and other nearshore ground-dwelling species.

Crab fishing communities that diversify their catch will fare better during future climate disruptions, the results suggest, just as investors who diversify their holdings are more likely to avoid financial ruin after a market crash.

It’s not surprising that people either stopped fishing or switched to other species after the crab fishery shut down, said Malin Pinkus, a marine ecologist at Rutgers who was not involved in the study. But what isn’t so obvious is that their behavior was predictable, he said.

Fishing communities with multiple connections to other fisheries were much less vulnerable to climate shocks. And that connectivity, a measure of diversification, Pinksy wrote in a commentary on the PNAS paper, “provides a key predictor for where climate shocks will be felt most extremely.”

Despite diversification’s clear benefits, however, crab specialists may resist branching out because they can make more money in the short term focusing on crab.

If one fishery is particularly profitable, like lobster or crab, everyone’s going to do it, said Pinsky, describing a phenomenon known as a “gilded trap.” But that means they don’t maintain options to fish other species. So if something happens to that golden goose, he said, “they’re out of luck.”

Fisher said the study results can’t predict exactly what will happen during future shocks. “But they do suggest what coping strategies already in use might guide policy,” she said.

Policies that create incentives to help fishermen avoid gilded traps, diversify fishing options and establish links between fisheries, for example, could facilitate “climate ready” fisheries management strategies.

The multiyear marine heat wave offered a preview of what’s in store under climate change, Pinksy said. “In many ways it’s our fire drill. And it’s important for us all to learn from it.”

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