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Urchin loss feeds crab population

Study sees upset in ocean system

PORTLAND, Maine — A boom that saw Maine fishermen harvest millions of pounds of sea urchins for the lucrative Japanese market depleted the spiny sea creatures, turning the ecosystem upside-down and creating an ideal habitat for an urchin predator that has flourished, according to a new scientific study.

The urchin bonanza of the 1990s triggered an ecological chain reaction that ‘‘flipped’’ the ecosystem from one with a stable amount of kelp and ­Jonah crabs to one with an overabundance of kelp and crabs and a lack of urchins, the study said.

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The urchin population might not recover unless fishery managers find ways to ­increase the number of fish that prey on Jonah crabs, whose strong numbers have been preventing the urchin population from rebounding, researchers said.

What has happened with ­urchins underscores the need for ecosystem-based ocean management, where regulators recognize that the rise or fall of one species can affect the rise or fall of another, said Robert ­Steneck, a professor at the University of Maine’s Darling ­Marine Center who led the study.

‘‘This kind of ecological inter­action was the impetus for President Obama’s initiative in 2010 to move the country toward ecosystem management,’’ Steneck said. ‘‘We have been ignor­ing strong interactions among species for decades. This is a great example of how it’s more complicated than just assuming that by reducing fishing mortality rates on a managed species, it’s going to recover.’’

The paper, ‘‘Ecosystem Flips, Locks, and Feedbacks: The Lasting Effect of Fisheries on Maine’s Kelp Forest Ecosystem,’’ appears in the latest edition of the Bulletin of Marine Science, a peer-reviewed journal published by the Rosenstiel School of Marine and Atmospheric Science at the University of Miami.

The paper was written by a research team that included three University of Maine graduates who at one time studied under Steneck.

In addition to Steneck, coauthors were Douglas McNaught of the University of Maine at Machias, Amanda Leland of the Environmental Defense Fund in Washington, D.C., and John Vavrinec of the Pacific Northwest National Laboratory in ­Sequim, Wash.

Sea urchins used to be a pest in Maine’s coastal waters, destroying kelp beds and clogging lobster traps. But that changed in the late 1980s when processors developed markets in ­Japan for the urchin roe, or uni.

With a gold rush mindset, thousands of fishermen harvested the globular spiny creatures from the ocean bottom by hand or in devices dragged behind their boats. Hundreds more people worked at processing plants along the Portland waterfront.

For three years straight, the harvest exceeded 30 million pounds, with a peak of 42 million pounds in 1993. The fishery was valued at more than $30 million, making it the state’s number two fishery behind lobster.

But the catch fell sharply in ensuing years as the urchin population shrank. In 2012, the catch was 1.8 million pounds, the smallest harvest since 1987.

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