Mobility of tropical tunas and the implications for fisheries management

We apply an advection-diffusion reaction model to data from three different tuna tagging experiments in the western and central Pacific Ocean (WCPO) to reexamine the question of to what extent the population dynamics and spatial characteristics of tropical tunas require international cooperation for effective management. The median lifetime displacement of skipjack ranges from 420 to 470 nautical miles. The lifetime displacement of yellowfin is about 20% less. The median half-life, a measure of residence time, of skipjack and yellowfin in WCPO exclusive economic zones (EEZs) is 3-6 months. Fishing decreases the lifetime displacement and decreases the half-life. We conclude that international arrangements between neighboring EEZs are essential for effective conservation, but that Pacific Island countries can achieve benefits from domestic conservation and fishery development policies. (C) 2002 Elsevier Science Ltd. All rights reserved.