Dueling Decapods: Observing Aggression Levels In One-On-One Interactions Between The European Green Crab Carcinus maenus And The Asian Shore Crab Hemigrapsus sanguineus In The Gulf Of Maine

Abstract

European green crabs Carcinus maenus have invaded the shores of the Gulf of Maine since the early 1800’s, devastating native crab populations in the sandy shores and rocky intertidal zones. In the early 2000’s the Asian Shore Crab Hemigrapsus sanguineus was introduced to the Gulf of Maine, and has since dominated rocky intertidal zones, overtaking the green crab populations in those areas. A study performed at the Cat Cove Marine Lab at Salem State University looked into the level of aggressive behavior between these crab species. An individual of each species was introduced into a round glass arena (1.65 L in volume, 16.5 cm in diameter), lined with a thin layer of sand to replicate a sandy shore, and shucked blue mussel, Mytilus edulus, placed in the center to attract the crabs. The crab-on-crab interactions were videotaped for 6 minute intervals, then statistically analyzed using numbers assigned to specific aggressive traits in each minute segment. The data showed that the European green crab was 11.56 times more dominant than the than the Asian shore crab in all of the trials combined. This information can be utilized to understand the behavior of the two invasive species and why Asian Shore Crabs are outcompeting the European Green Crab populations in rocky shorelines.