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News Release
Lined shore crab. Photo taken during the study.
Lined shore crab. Photo taken during the study.
Oregon Scientists Observe Northward El Niņo Expansion of Crab Species, Impact on Indigenous Snails (Photo) - 11/19/20

COOS COUNTY, Ore. – New research out of South Slough National Estuarine Research Reserve suggests northward shifts of the lined shore crab may threaten vulnerable snail populations along the northern Pacific Coast.

The study, conducted by researchers from the University of Guelph, Oregon State University, South Slough Reserve and the Oregon Institute of Marine Biology focused on the lined shore crab, a species typically found between Baja California, Mexico and Southern Oregon. The crab has evolved shell crushing capabilities to feed on the thick-shelled snails commonly found in such tropical regions.

Among the lined shore crab’s prey is the Sitka periwinkle, a snail that lives along the northern Pacific coast. Typically, the two species live in separate regions; however, the study suggests the lined shore crab’s range expands north during El Niño events, which cause a strong ocean undercurrent that runs northward. The undercurrent transports lined shore crabs outside of their usual range and into areas where indigenous species, like the thin-shelled Sitka periwinkle, are ill-equipped to protect themselves from such predators.

In addition to tracking the prevalence of the lined shore crab in Oregon, Washington and Vancouver Island, Canada, the team also conducted laboratory experiments to test the threat the crabs pose to the Sitka periwinkle. The snails’ defenses were ineffective against the lined shore crabs, which were able to eat ten times more Sitka periwinkles, compared to crabs that are commonly found along the northern Pacific coast.

The research suggests that advancing lined shore crabs may pose an immediate threat to thin-shelled gastropods, such as the Sitka periwinkle. The team also assessed a scenario in which the lined shore crabs permanently establish farther north. Their findings suggest Sitka periwinkle populations may only survive in areas where the lined shore crabs are less likely to establish.

The lined shore crab is one of many aquatic species along North American coastlines that is advancing north as the ocean warms.

“We need to understand the impact of northward migration,” said Dr. Shon Schooler, Lead Scientist at South Slough Reserve. “The disappearance of Sitka periwinkle populations may change parts of the food web. Additionally, decreases in diversity can reduce ecosystems’ resilience to environmental change, like natural disasters."

The findings were published in the Canadian Journal of Zoology earlier this year.


The South Slough National Estuarine Research Reserve (South Slough Reserve) is a 5,900-acre natural area located in the Coos estuary on the south coast of Oregon. The Reserve was designated in 1974 as the first unit of the National Estuarine Research Reserve System (NERRS) and is affiliated with the Oregon Department of State Lands and the National Oceanic and Atmospheric Administration (NOAA). The Reserve supports and coordinates research, education and stewardship programs that serve to enhance a scientific and public understanding of estuaries and contribute to improved estuarine management.

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