Effect of increasing size on the ability of green crab (Carcinus maenas) to manipulate and eat commercially and ecologically important species in the Pacific Northwest

We sought to determine the potential effect of invasive green crab (Carcinus maenas) on commercially and ecologically important species in the Pacific Northwest through choice and no-choice assays conducted with green crab of different sizes. We looked at the feeding behavior of green crab in relation to various prey choices, including adult Manila clam (Ruditapes philippinarum), adult Pacific oyster (Crassostrea gigas), young Pacific oyster as spat on shell, and native eelgrass (Zostera marina). No-choice assays were modeled with a negative binomial regression, and choice assays were modeled with a logistic regression. Results from the no-choice model reveal that the interaction of claw size and prey type was significant, and green crab of all sizes fed on spat of Pacific oyster on shells. Results from the choice model indicate that sex was not significant in predicting whether green crab consumed any prey type. In our study, green crab that fed exclusively on 1 prey type chose spat on shell or eelgrass over adult prey items. On the basis of the data, we suggest that growers focus on protecting spat of Pacific oyster from all sizes of green crab over protecting adult Pacific oyster if resources are limited.