Requirements and alternatives for the limitation of fishing capacity in tuna purse-seine fleets

摘要

Most stocks of tunas are hilly exploited, and two stocks, Atlantic bluetin and southern bluefin, are clearly overexploited. With the exception of skipjack, increased fishing effort for the principal market species of tunas will not result in sustainedincreases in catch, and would probably lead to reduced catches over the long term. It is clear that controls on the amount of fishing mortality exerted on most of the stocks of tuna are needed. Controls on tuna fishing are administered principally by five international organizations, the Inter-American Tropical Tuna Commission, the International Commission for the Conservation of Atlantic Tunas, the Indian Ocean Tuna Commission, the Commission for the Conservation of Southern Bluefin Tuna and the Commission for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean. Two types of controls are possible, input controls, such as restrictions on the numbers of fishing vessels or the periods during which fishing is permitted, and output controls, such as catch quotas or limits on the sizes of individual fish that can be retained. There is general agreement that input controls should be the principal method for limiting fishing mortality; specifically, fishing capacity must be limited. This can be accomplished in various ways. Regional vessel registers can limit the numbers and capacities of vessels permitted to fish in a region, and a global vessel register can limit the numbers and capacities of vessels permitted fish anywhere in the world. Such limits can be in the form of use rights, which, under certain circumstances, should be tradeable. Buybacks of excess vessels can reduce or eliminate the economic hardships for the owners of vessels that are notpermitted to fish. Limitations on fishing mortality can also be accomplished by quotas to nations or to vessel owners or by licensing. Quotas or licences can be bought and sold. During the initial phase of capacity limitation programs additional output controls may be needed to ensure effective management and conservation. Limitations on fishing capacity, regardless of how they are accomplished, are beneficial from the standpoints of both economics and conservation of tunas and other species caught by the fisheries for tunas.