Size Selectivity under Noncooperative Harvest: When Does Management Improve the Value of the Fishery?

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.We describe the dynamics by which competing harvesters selectively target prime market-sized fish, without internalizing the externality of increasing targeting costs, as the abundance of prime fish decreases. Due to the increasing targeting costs for prime size, harvesters continually target the next-most-desirable size fish, gradually fishing down the size structure of the population until the change in targeted value balances a decrease their harvesting costs. Furthermore, we show that when harvesters are heterogeneous in their ability to transform larger fish into more valuable products, the decreasing size structure disadvantages harvesters with more responsive production technologies and decreases the economic efficiency of the fishery. Importantly, it is not always optimal for a fishery manager to segregate heterogeneous harvesters, and leave prime fish for harvesters that value them the most. The fishery manager faces a tradeoff between decreasing the rate of growth of the biomass, increasing the costs of less responsive harvesters, and facilitating the harvest of large prime fish by more responsive harvesters. We illustrate the conditions when a benevolent fishery manager can increase net present value by segregating harvesting, and conversely, conditions when the competitive harvesters engage in near-optimum strategies. The implication is that the importance of heterogeneous values, and size selectivity, varies depending on the biological and economic conditions of particular fisheries