Asian Shore Crabs Changing Bay Ecology

Wikipedia Photo.
Wikipedia Photo. Niels-Viggo Hobbs has spent a great deal of time in recent years exploring tide pools and the rocky shoreline of Rhode Island, and he said that the ecology of the shore has changed dramatically in the past two decades because of one relatively recent invader: the Asian shore crab.

“Twenty years ago if you went to the rocky shore and turned over rocks, you would have found mostly one or two species of native crabs,” said Hobbs, a doctoral candidate at the University of Rhode Island. “But within a year of the Asian shore crab showing up in Rhode Island in 1998, if you turned over those same rocks, you’d have something like 20 or 30 Asian shore crabs.”

This dramatic change in the composition of crabs in the region may have far-reaching implications for the ecology of Narragansett Bay. Many of the native crab species in Rhode Island are difficult to find. Some have been pushed into deeper water, where they are preyed upon by fish and other species they seldom encountered in the past. Others, such as the spider crab, seem to be unaffected by the invaders.

Asian shore crabs aren’t large—their shells are typically an inch or less across—but they reproduce quickly and are more tolerant of cold and being out of the water than the region’s native crabs. Hobbs said a 1-meter area that may have harbored a dozen native crabs 2 decades ago now harbors hundreds of Asian shore crabs.

“They eat whatever they can get their claws on, and they reproduce like crazy, so they have a lot of mouths to feed,” he said. “But they also become food for other marine life as well.”

Read more about the invasive Asian shore crabs in Rhode Island: