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Hard Clam Populations May Decrease Due to Stone Crab Range Shifts

NCCOS-funded research into the ecosystem effects of climate change may improve management of the commercially important shellfish populations in a warming climate. Stone crabs (Menippe mercenaria), normally found only in South Atlantic estuaries, are moving northward into the mid-Atlantic due to warming temperatures. This pole-ward range shift is predicted to increase interactions between stone crabs and other crab species.

NCCOS-sponsored researcher Melissa Wong (University of North Carolina Institute of Marine Sciences), funded under the Ecological Effects of Sea Level Rise Program documents that stone crabs and blue crabs, when foraging on hard structures such as those constructed to reduce shoreline erosion from rising sea levels, both readily consume small hard clam (Mercenaria mercenaria) sizes (10-30 mm) while only stone crabs are efficient predators of larger hard clam sizes (30-60 mm), which blue crabs avoid.

In a climate-changed mid-Atlantic estuary, stone crabs will consume a wide range of clam sizes, and the size refuge large clams usually have from blue crab predation will be lost. The long-term implications for crab and clam populations is uncertain.

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