Habitat-Fisheries Interactions and Destructive Fishing

Suggested Bibliographic Reference: Challenging New Frontiers in the Global Seafood Sector: Proceedings of the Eighteenth Biennial Conference of the International Institute of Fisheries Economics and Trade, July 11-15, 2016. Compiled by Stefani J. Evers and Ann L. Shriver. International Institute of Fisheries Economics and Trade (IIFET), Corvallis, 2016.Proceedings of the Eighteenth Biennial Conference of the International Institute of Fisheries Economics and Trade, held July 11-15, 2016 at Aberdeen Exhibition and Conference Center (AECC), Aberdeen, Scotland, UK.The state of habitats is important for their productivity, including for stocks of commercial fish. Some fishing methods can damage habitat or give bycatch of species. Destructive fishing gear has sometimes been introduced without awareness of the direct negative impacts on habitat, and without realising the possible negative indirect impacts on the commercial fishery itself. We present a model to investigate destructive fishing practices on general habitat or other species than those of commercial interest, when there is a biological interaction to the commercially interesting specie. It includes a logistic biomass-model of commercial fish stock and habitat, a non-essential dependence between habitat and fish stock, and Schaefer harvest functions of fishing both on the commercial stock and the habitat. In the conceptual model habitat can also be interpreted as a species. We give an analytical measure of the impact of being ignorant to the destructive effects of new fishing gear, both compared to the use of non-destructive gear and to optimal management with the destructive gear. The use of new fishing gear is often motivated by improved cost-efficiency. For non-destructive fishing this depends only on changes in catch efficiency and unit cost of fishing effort. When there is destructivity and habitat interaction the condition for actual improvement in fishing cost efficiency is more complex. We define this and show how much relatively larger the "simple" measure of fishing cost efficiency must be for different degrees of destructivity and interaction to give a real improvement in fishing cost efficiency