Multispecies modeling of the Georges Bank fish community
Georges Bank is a highly productive marine ecosystem with a long history of exploitation. This ecosystem has undergone profound changes in fish abundance and species composition in the past three decades. In this dissertation, I applied multispecies virtual population analysis to the Georges Bank fish community to evaluate the combined effects of harvesting and predation on the fish-community structure. By applying MSVPA to nine commercially and ecologically important fish species on Georges Bank, I estimated predation mortality of prey species, fishing mortality, and population abundance from 1978 to 1992. The results indicated that predation mortality on the prey species was highest at ages 0 and 1 and was much higher than the fishing mortalities for these species. As a consequence, recruitment levels were mediated by predation. The sensitivity of MSVPA to perturbations in the inputs was assessed with a two-level fractional factorial experimental design that included ten factors and nine response variables. Results of the sensitivity test indicated that MSVPA model outputs were most sensitive to predator consumption rates and terminal fishing mortalities. ^ In this study, I evaluated the consequences of different harvest policies under single and multispecies models by constructing an adaptive management framework for the Georges Bank fish community. The single-species virtual population analysis and two multispecies virtual population analysis runs based on two different sets of predator-consumption rates were used as alternative hypotheses to describe population dynamics; these three models were used to evaluate three harvest policies. The sum of cumulative revenues over species was used as a criterion to evaluate the performance of each hypothesis-policy combination in the adaptive-management framework. The best harvest policy was a conservative policy that allowed the valuable demersal species to recover and maintain a sustainable yield. ^
Biology, Oceanography|Agriculture, Fisheries and Aquaculture
"Multispecies modeling of the Georges Bank fish community"
Dissertations and Master's Theses (Campus Access).