BIOECONOMICS AND CATCHABILITY - FISH AND FISHERS BEHAVIOR DURING STOCK COLLAPSE

During periods of stock collapse, an increase in the catchability exhi bited by many small pelagic fish is a consequence of two factors: thei r schooling habit and the remarkable efficiency of today's technology intensive fishing fleets. The net result is that a virtually constant catch per unit effort may be achieved regardless of stack size. Three models of catchability used to highlight the consequences of fish beha viour and fishing technology during stock collapse (Pitcher, 1995) are extended to examine the effects of incorporating profit motivated eco nomic behaviour of fishers. Three scenarios are examined: (1) cooperat ion by fishers to achieve maximum economic yield (MEY); (2) non-cooper ation resulting in open access equilibrium; (3) non-cooperation with a llocation of subsidies allowing fishers to increase effort beyond the open access equilibrium. Incorporating economic behaviour in the densi ty-dependent catchability models may result in an alarming increase in the rate of stock depletion, since fishers maintain high profits even during low stock abundance. We discuss the consequences of using a mo del where catchability is assumed constant for the management of fishe ries on small schooling pelagic fish. (C) 1997 Elsevier Science B.V.