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Are we using herring to farm lobsters? The effects of herring bait on Lobster growth and diet composition.
Grabowski, Jonathan*,1, Clesceri, Erika1, Baukus, Adam1, Yund, Phil1, 1 University of Maine, Darling Marine Center, Walpole, Maine, Walpole, Maine
ABSTRACT- Lobster (Homarus americanus) landings in the past two decades have been higher than traditionally thought to be sustainable in the Gulf of Maine. Given the economic value of the lobster fishery in Maine and the socioeconomic consequences of a potential fishery collapse, determining the importance of herring bait to lobster population dynamics is of critical importance. To evaluate whether the annual subsidy of herring bait in the nearshore waters of Maine are contributing to lobster production, we compared stomach contents and stable-isotope ratios in the tissues of lobsters from closed (Monhegan Island) and open (Georges Islands) fishing areas off the coast of Maine in the summer and fall of 2002. We also quantified growth rates in both regions using mark-recapture experiments to assess if the presence of herring bait in fished areas increases short-term growth of lobsters. Diet composition of lobsters in fished areas consisted of substantially more herring bait than lobsters in areas closed to fishing. Larger sub-legal lobsters (65-83 mm carapace width) in closed areas consumed more of their natural prey (i.e., crabs, urchins and mollusks) than similar sized lobsters in fished areas. Recaptured lobsters from fished areas grew substantially more than those in areas closed to fishing, indicating that in the absence of herring bait, food may limit lobster growth in the Gulf of Maine. In addition, these results suggest that herring bait influences the diet and growth of lobsters as well as may impact benthic community structure in the Gulf of Maine.
Key words: Diet Composition, Resource Limitation, American Lobster, Herring Bait