Exposed and vulnerable, half a dozen dime-sized crabs dart for cover. Their striped legs move them sideways across the sand as they search for places to hide. Some crabs disappear into crevices among nearby rocks, while others attempt to conceal themselves by burrowing into the beach. The crab’s mottled dark brown and green carapace provides effective camouflage against the wet rocks and scattered aquatic vegetation, but is still no match for the savvy hands of the Westbrook middle-school students who are grabbing them and dropping them into buckets. Another rock is overturned, and crabs
scatter like cockroaches suddenly exposed to light. The kids react quickly, and additional specimens are collected. The tide is low, and the slippery rocks along Meigs Point at Hammonasset Beach State Park make for unsure footings, but this group of sixth and seventh graders is on a mission. They need to collect 50 crabs from their designated quadrant, and record the crabs length and sex before the autumn sun sets. Julie Ainsworth is leading this scientific field trip offered by Bauer Park and the Madison Beach and Recreation Department. Assisting Ainsworth is Westbrook teacher Cathy Lepore, and her band of volunteer students. Together, they are participating in a multi-national study to document the spread of the Asian shore crab, an invasive species rapidly besieging the East Coast of the U.S. Ainsworth says “Things that are non-native may not necessarily be bad, but the thinking with this crab is that they are more troublesome.” David Delaney, a Ph.D. candidate at McGill University in Quebec, organized the study in an effort to predict the spread of non-native crab species, such as the European green crab and the Asian shore crab, and to validate the effectiveness of citizen scientists to collect research data. Ainsworth became involved in the study about three years ago, after responding to an open call to educators along rocky shorelines. Delaney met with Ainsworth and her Nature Club at Bauer Park, and provided all the necessary instruction and collection materials. Now several times a year, Ainsworth calls on her crew of budding marine scientists to scour the beach and collect crabs. Their data, along with data from a thousand other volunteers, is compiled and analyzed by Delaney. The inch-and-a-half long Asian shore crabs thrive in the rocky inter-tidal zone; the area between the high tide line and a couple feet below the low tide limit. They are voracious feeders, and their diet consists of salt marsh grass, small invertebrates, mussels, clams and the green crab. Ainsworth notes why this crab is so prolific “They can withstand huge temperature and salinity ranges, as well as low oxygen levels.” She adds, “Females have a much longer breeding season than other species of crab. It seems like they are reproducing so fast that they can dominate very quickly.” Female crabs produce 50,000 eggs per clutch and are capable of producing 3-4 clutches per breeding season. In just 18 years, the Asian shore crab has become the predominant crab along the rocky Connecticut shore, and has effectively replaced the European green crab, another non-native but larger crab species which arrived in the 1800s. The pace that this crab is spreading is astonishing. Ainsworth mentions a recent study which showed “Blue mussels are actually evolving thicker shells in response to the Asian shore crab. They (Asian shore crabs) are definitely having a sudden impact.”