Preliminary Resource Assessment of Yellowfin Tuna (Thunnus Albacares) in the Western Indian Ocean by the Stock-Fishery Dynamic Model

Abstract

Yellowfin tuna (Thunnus albacares, YFT) in the Indian Ocean has been exploited for more than 200 years (Anderson and Hafiz, 1985), while official statistics are available for some 40 years. In this region, the YFT resource has been commercially important as a protein source for both developing and developed countries. Hence, it is essential to manage and conserve YFT resources properly for future generations. To this end, an assessment of the YFT stock is presented in this paper, in order to provide fundamental information for its management. More than 80% of the YFT catch from the Indian Ocean comes from the western part (Figure 1), so this assessment is focused on that part. In this study, the stock structure of the Indian Ocean YFT is assumed to be two major (western and eastern) stocks and two minor stocks (far western and far eastern), as depicted in Figure 2a (Nishida, 1992). Hence, the assessment is focused to the western stock. The defined boundary of the western stock is depicted in Figure 2b; it is similar to FAO Area 51 (Figure 1) except for the western boundary.