Preliminary analysis of billfish catch rates in the Indian Ocean.

Abstract

Due to the general lack of targeted fisheries on billfish, the resource status of these species within the Indian Ocean has not been analysed in any previous study and currently remains unknown. Nevertheless, significant quantities of billfish are caught annually in the Indian Ocean and, being generally long lived, these species remain vulnerable to overfishing. In this paper preliminary indices of stock availability are presented for the main billfish species based on the catch and effort data pertaining to the Japanese and Taiwanese Indian Ocean longline fisheries. While the indices need to be treated with some caution (due to problems relating to the accuracy of the catch and effort data, and the fact that changes in catchability have not been factored into the analyses), the declines observed in the indices for black marlin, striped marlin and sailfish/spearfish warrant further investigation. In particular, further effort needs to the put into accounting for changes in targeting practices and the other changes in the fishing gears used.