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Study finds littleneck clams declining in Salish Sea, West Coast

December 23, 2018

A recent study evaluating shellfish populations on area beaches found that native littleneck clams have declined over the past several decades, most likely due to ocean conditions rather than local impacts.

Littleneck clams are one of several commercially and recreationally important species in the region.

Pinpointing whether local impacts, such as harvesting and pollution, or large-scale ocean conditions are influencing area shellfish populations can help guide management of the species.

“Studies like these allow managers to consider which environmental factors have the greatest impact on our local clam populations,” Lorraine Loomis, fisheries manager for the Swinomish Indian Trail Community and chair of the Northwest Indian Fisheries Commission, said in a news release.

The study also highlighted that population changes were most prominent across species, rather than by beach.

Littleneck clams, for example, declined similarly throughout the area included in the study, but other shellfish species studied did not similarly decline at the same beach locations.

The study was co-authored by the Swinomish tribe’s Fisheries Department, the Skagit River System Cooperative and the state Department of Fish and Wildlife.

It was published this month in the research journal of theAssociation for the Sciences of Limnology and Oceanography.

The study evaluated three kinds of shellfish on 11 beaches using about 28 years of data compiled by Fish & Wildlife.

The northernmost beaches evaluated were at Whidbey Island’s Penn Cove and Camano Island State Park. The southernmost was near Olympia.

In addition to native littleneck clams, butter clams and heart cockles were also included in the study.

Julie Barber, senior shellfish biologist for the Swinomish and co-lead author of the study, said the overall decline seen in littleneck clams suggests that large-scale ocean conditions are affecting the species.

“Our research implies that one or more large-scale factors, such as disease, the North Pacific Gyre Oscillation (a cyclical change in ocean conditions) or climate change are driving the concerning pattern of (decline) seen in native littlenecks,” she said in the release.

The study also examined findings from past research throughout the West Coast, which showed similar declines.

“To our knowledge, this is the first study to combine information from Alaska to California and conclude that native littlenecks are likely declining across their entire range,” Barber said.

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