Date of Award
Master of Arts in Marine Affairs
Currently, most fisheries management bodies utilize a narrow, single-species focus in decision-making processes. These methodologies, however, fail to recognize the interrelated nature of ecosystems, and as such are unable to produce realistic and valid estimates of sustainable yield. One proposed method of integrating ecosystem data into the decision-making process of fisheries management involves quantifying ecosystem diversity. This study evaluates historical fisheries management success in terms of changes in biological diversity and evaluates the potential use of length and species diversity measurements to aid managers in understanding fishery-induced community changes. To evaluate these relationships, a comparison of ecological and management outcomes of the Georges Bank and Eastern Bering Sea groundfish fisheries was performed. These ecosystems were selected due to the strong importance groundfish fisheries play in both regions. Fisheries on Georges Bank are generally considered to be among the world’s most poorly managed and are considered to be in a state of severe decline. In contrast, Alaskan fisheries are generally considered to be among the most successfully managed in the world.
Fishery independent survey data from Georges Bank and the Eastern Bering Sea were evaluated for at least an eighteen year period. Changes in the proportion of length distributions, mean length, and maximum length of annual trawl catches were evaluated for the entire catch and particular species of interest. Annual measurements of species diversity were quantified through the use of species richness, evenness, and trophic diversity calculations and overall trends were evaluated between the ecosystems.
Results indicate that fishing pressure is correlated to fish size distributions in both ecosystems, however the relationship between fishing pressure and species diversity is slight in both ecosystems. Additionally, a surprising trend of increasing species diversity is apparent in both ecosystems, despite the simultaneous decline of several stocks on Georges Bank. Lastly, an evaluation of management approaches revealed that management of the Georges Bank region has been largely reactive, responding to immediate ecological needs of the fishery. In the Eastern Bering Sea, groundfish management has been comparatively proactive, seeking to address needs of the fishery prior to reaching critical management points. These differing management styles are apparent in the ecological assessments of both ecosystems. Frequently, the reactive management actions on Georges Bank resulted in more immediate responses in single species abundance and ecosystem diversity, while the more proactive management actions in the Eastern Bering Sea resulted in little ecological change in the system. These results highlight the importance of utilizing a proactive approach to fisheries management and suggest that changes in ecosystem and community composition should be strongly considered in all management actions to gain a more holistic perspective. Furthermore, they suggest that management goals related to the maintenance of biological diversity may not be suitable because of inadequate understanding of community dynamics.
Foley, Catherine M., "A Difference in Perspective: A Comparison of Ecosystem and Single-Species Focused Fisheries Management" (2013). Open Access Master's Theses. Paper 45.