Asian Shore Crab Research Paper

The invading Asian shore crab (Hemigrapsus sanguineus), has been a growing cause for concern for over a decade in Southeastern Massachusetts. It is suspected that the species was first introduced in the U.S. as adults or larvae present in ballast water discharged from incoming global trade ships. The first specimen in the U.S. was recorded in Townsend Inlet, Cape May County, NJ in 1988. The first appearance in Massachusetts was near Woods Hole on Cape Cod in 1992. By 1994, the Asian shore crab was identified in my hometown of Fairhaven, MA. As a precautionary measure, the ballast water of incoming international trade ships are monitored to prevent and eradicate new introductions of the species. Researchers are also conducting experiments to
When a second invasive species is introduced in the same environment the effects can become magnified tremendously, creating a serious cause for concern. 1 The European green crab (Carcinus maenas) invaded the Atlantic waters of North America in the early 1800s. The green crab is an omnivorous predator and has shown consumptive and noncomsumptive impacts throughout local ecosystems. 1 These same ecosystems were invaded two decades ago by a second omnivorous predatory crab, the Asian shore crab (H. sanguineus). Today, the Asian shore crab is well established and is becoming a dominant crab species in Massachusetts, as well as much of New England. The species has become such a threat because it can tolerate vast ranges of salinity and temperature, is an opportunistic omnivore with a broad diet, females have a high fecundity with a breeding season twice as long as native crab species, and there are no natural predators in the non-native range. A broad diet creates the potential to significantly disrupt the food web, ultimately affecting indigenous crab, fish and shellfish species. A steady increase in population since being introduced raises concerns of how this species is affecting the ecosystem and native
maenas is cannibalistic, especially in postlarval and juvenile stages (Moksnes et al., 1998). This cannibalism tends to be density dependent and self-regulates populations of C. 5 maenas (Moksnes, 2004). Mortality by means of predation by H. sanguineas serves to further thin populations. C. 5 maenas is also very efficient in selecting habitats with low risk of predation (Moksnes, 2002). H. sanguineus populations are at higher densities in rocky intertidal areas, the same refuge habitat preferred by juvenile C. maenas. In response, C. 5 maenas has shifted habitat usage to areas with reduced refuge (Jensen et al. 2002). 5 This habitat shift also creates a shift in diet in adults from primarily consuming mussels to primarily consuming red algae (Griffen et al., 2008). Reduced refuge creates risk of predation by seabirds, fish, and other predators. Dietary shifts of C. 5 maenas in the presence of H. sanguineus could reduce C. maenas populations in two ways. First, this shift in diet decreases nitrogen consumption which slows growth rates of C. 5 maenas, potentially extending the time susceptible to size dependent predation (Griffen, 2008). In the presence of H. sanguineus, C. maenas typically forages for red algae (Chondrus crispus) containing 0.4%-1.4% nitrogen with higher values in winter and lower in summer (Chopin and Floch, 1992). Otherwise, C. maenas would prey on mussels (Mytilus edulis) containing 7.7%-9.6% nitrogen with higher values in spring and lower in late