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Feeding Frenzy: West Coast Anchovy Boom Masks Ecosystem in Peril

As anchovy populations crash in the ocean, the surviving forage fish move close to shore, attracting record numbers of whales and other marine life to an all-they-can-eat banquet. But scientists say the bounty is not sustainable.

Written by Alastair Bland Published on Read time Approx. 4 minutes
A humpback whale breaches off Long Beach in California. Nick Ut/AP

The Golden Gate Bridge this year became a de facto wildlife-watching platform. For months, humpback whales, feeding on schools of anchovies, swarmed in the churning currents below San Francisco’s famed landmark while crowds of tourists ogled the giant marine mammals. The phenomenon seemed a repeat of 2016, when whales lingered for months under the bridge, in San Francisco Bay and close to shore along much of California’s coastline.

Whale watching tours have encountered hundreds of whales in a day, and small coastal coves have often contained several dozen humpbacks at once. The sight of lunge-feeding whales erupting from the ocean, often only yards beyond surfers, has become just another day at the beach. Joining the whales have been sea lions, dolphins and squadrons of dive-bombing brown pelicans, all feeding on schools of anchovies so thick they darken the water for acres.

But some biologists warn this image of a thriving marine ecosystem is actually a strange sort of mirage. While California sea lion and humpback whale numbers are, in fact, up – probably higher than they’ve been in many decades – the anchovy population is not.

The stock has collapsed, according to William Sydeman, president and senior scientist at the Farallon Institute, a nonprofit marine research organization in Petaluma, California.

“The abundance we’re seeing nearshore is an illusion,” he said. “The anchovies are only occupying about 10 percent of their habitat. When they’re abundant, they range offshore. When they’re not abundant, they contract their range toward shore.”

In other words, the less plentiful anchovies become, the more visible they – and the animals feeding on them – are to people. Sydeman says the result of this peculiar phenomenon has been an extreme visual deception.

In fact, there haven’t been so few anchovies off California’s coast in 20 years, according to a study he coauthored, which was published in 2017 by the California Cooperative Oceanic Fisheries Investigations. The research shows that throughout the 1990s, between 100,000 and 400,000 metric tons of mature anchovies swarmed off the coast of California and northern Mexico. In 2005, the spawning-age biomass spiked to about 2 million metric tons.

Then, the population nosedived. Sydeman and his coauthors reported that for several years the biomass remained barely over 20,000 metric tons. That’s a dismal count for what biologists consider to be one of the most important fishes in the ocean, thanks to its general abundance, its high nutrition values and its snackable size. Sydeman notes that 75 larger species feed on anchovies in coastal waters, among them, salmon, halibut, thresher shark and lingcod.

The decline, scientists seem to agree, has had little to do with fishing pressure and more to do with changes in ocean productivity. Indeed, forage fish populations are known to cycle up and down naturally. Moreover, they have the potential to rebound quickly, and Sydeman says there may now be as many as 150,000 metric tons of anchovies off California.

Still, California’s anchovy population remains below the historic average, and this is especially concerning since other key forage species have also declined. The Pacific sardine population has plunged by approximately 95 percent in a decade, according to a recent assessment by the National Marine Fisheries Service (NMFS). The San Francisco Bay herring run, too, has dipped to about a third of its long-term average biomass, according to surveys from the California Department of Fish and Wildlife.

The decline of these species has sent shockwaves through the ecosystem, causing mass starvation and breeding failures in California sea lions and brown pelicans, respectively.

John Calambokidis, cofounder of the Cascadia Research Collective in Olympia, Washington, says food limitations could also impact humpback whales, whose numbers have exploded by 400 percent over the past 30 years. He notes that researchers have identified about 3,000 individual humpbacks along the United States’ West Coast.

“With the decline in the prey base and the growth in the humpback population, there is the potential for stress on the population,” Calambokidis said.

How diminished the anchovy population is remains a matter of debate. In 2016, the National Marine Fisheries Service released a report that took issue with Sydeman and his colleagues’ estimate of anchovy populations.

Josh Lindsay, a fishery policy analyst with the NMFS, said the egg and larvae counts used in Sydeman’s analysis could be inaccurate.

“Not everyone agrees with the method used in their survey,” he said. “It might be helpful for identifying localized trends but not for estimating the entire population.”

But even NMFS has calculated low local anchovy abundance. In 2015, the agency’s own scientists found that the stock could be as small as 31,427 metric tons. The group Oceana has since sued the agency for allowing the commercial fishery to take up to 25,000 tons per year. The case goes to trial in January.

“They’re authorizing fishermen to take almost the entire estimated population,” said Geoff Shester, Oceana’s California campaign director.

But California anchovy fishers rarely, if ever, catch the full quota. Moreover, the local fishery is small compared to that of, say, Peru, where fishers were catching 30,000 metric tons per day in 2015. In California, commercial purse seiners netted 11,586 tons of anchovy in 2014. Most of the catch is used as longline fishing bait and tuna feed, according to Shester.

Sydeman says that even though fishing pressure is relatively low, the harvest could be hindering a population rebound.

“When you have a population that’s down and subject to predation, you don’t want to be fishing them,” he said.

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