Date of Award
Doctor of Philosophy in Environmental and Natural Resources Economics
Environmental & Natural Resource Economics
This study investigates the biological and economic consequences of modifying the species selectivity properties of fishing gears in a multispecies context. The objective is to examine whether modifying the species selectivity properties can contribute to rebuild overexploited stocks. To meet this objective, conceptual and empirical bioeconomic models were constructed. The conceptual model was used to investigate the qualitative impacts and the empirical model was used to derive the quantitative impacts of modifying the species selectivity properties of the gear.
In the conceptual part of this study, a stylized model was developed to analyze the long-run equilibrium bioeconomic properties of modifying the species selectivity properties of the gears. The study examined two polar cases, namely when the gears were perfectly non-selective and perfectly selective.
The analysis showed that there was a considerable amount of uncertainty regarding the impact of technological improvement. Policy prescriptions for rebuilding stocks varied dramatically depending on the type of technology employed and the presence of biological interrelationships. In the perfectly non-selective gear case, rebuilding strategies would benefit from decreasing the catchability of the overexploited species as long as the stocks were biologically independent. In the presence of biological interrelationships, decreasing the catchability yielded ambiguous results. Other policies, such as increasing the catchability of accompanying species, and simultaneously decreasing the catchability of the target species and increasing the catchability of the accompanying species also generated ambiguous results.
In the empirical part of the study, a bioeconomic model of the Georges Bank multispecies fishery was constructed. The model had four species groups (roundfish, flatfish, elasmobranchs, and pelagics) and three gears types (otter trawl, gillnet and longline). The model evaluated the long-term biological and economic implications of changing the gear design or configuration (technology-based changes) and the creation of a tax-subsidy program (market-based changes).
Model results suggested that technological and market-based programs could aid in the rebuilding process; however, by themselves they are insufficient to recover the stocks. Rebuilding the overexploited roundfish and flatfish stocks requires significant reduction in fishing effort.
Donald, J. J. Agar, "Bioeconomic Implications of Modifying the Selectivity Properties of Fishing Gears" (2000). Open Access Dissertations. Paper 509.