Population Dynamics of American Lobster: Environmental, Ecological, and Economic Perspectives

This dissertation research focuses on how environmental (habitat model), ecological (stock-recruitment [SR] model), and economic factors (bioeconomic model) influence the population dynamics of the American lobster, Homarus americanus, in the Gulf of Maine (GOM). Temporal consistency in spatial distribution of lobster at large spatial scales suggests that the distribution may be regulated by environmental variables. I developed a statistical model to estimate season-, size-, and sex-specific lobster spatial distribution in the GOM based on habitat variables. This model is of significant value for American lobster management, providing a basic for predicting how their distribution could respond to environmental variability, an especially important consideration in a region of ongoing changing climate. It is well known in ecological studies that the choices of spatial scales can influence the possibility of detecting ecological patterns. I tested the hypotheses that the SR relationship for American lobster is detectable only at appropriate spatial scales. The best SR models were found at medium spatial scales but the scales varied for the SR models for eastern and western GOM, which have different oceanic conditions. This suggests that optimal spatial scale might be process-related. I demonstrated that the choice of spatial scale directly affected the possibility of identifying the SR relationship, the estimation of SR parameters, the type of SR relationships, and the predictive abilities of the SR models. Failure to consider potential behavioral changes of fishers with respect to changes in management initiatives may lead to unintended consequences that do not reflect management goals. I developed a bioeconomic model to evaluate effectiveness of different management strategies under different behavior assumptions of fishers for the Maine lobster fishery. I found that reducing trap limits might actually increase the total number of traps fished unless fishers do not change their behavior in response to trap reduction. Landing tax is robust to changes in fishers’ behavior and also the most effective strategy in terms of fishing effort reduction and harvest schedule modification and most importantly, increases the profit of the fishery. I demonstrated the importance of fishers’ behavior in determining effectiveness of the lobster fishery management