Assessing impacts of green crab (Carcinus maenas) on the abundance of American lobster (Homarus americanus) in nature

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University of New Brunswick


The overlapping vertical range of the American lobster (Homarus americanus) and the invasive green crab (Carcinus maenas) along the Western coast of North America offers the potential for predation by green crabs upon early post-settling and juvenile lobsters. I used three approaches to determine if green crabs affect the abundance of lobsters in nature: (1) predator enclosure experiment, (2) molecular analysis of green crab gut contents, and (3) model equation to assess rate of predation based on (i)- the molecular gut content analysis, (ii)- detectable DNA decay function and (iii)- green crab density. The first study suggested no impact of green crab on lobster, the second provided the first evidence of consumption by green crab on free roaming lobster in nature, and the third was ambiguous with respect to the magnitude of this predation. The model equation suggests the potential for large impacts by green crab, however, modifications to the sampling protocol are necessary to obtain a more precise estimate of predation.