Possible stock structure of dolphinfish (Coryphaena hippurus) in Taiwan coastal waters and globally based on reviews of growth parameters

Abstract

Dolphinfish (Coryphaena hippurus) is used by many coastal countries. Sustaining harvest of this resource will require cooperation among fishing countries in each region, and determining population structure is paramount to ensuring effective management. Examining life-history parameters (such as growth rate) is a useful and relatively inexpensive method for identifying possible stock units, which can be subsequently confirmed by other methods. The purpose of this study is two-fold. First, we examine the two-stock assumption for Taiwanese dolphinfish and the reliability of estimated growth curves based on seasonally-stratified growth performance indices. The von Bertalanffy growth functions (VBGF) were firstly estimated from 2005 to 2009 length frequency sample data of eastern and southern coasts of Taiwan. New growth performance indices were then calculated from the log-transformed parameters of the VBGF and examined by a simultaneous confidence region (SCR) under the assumption of bivariate normal distribution. Second, we summarize VBGF parameter estimates from all regions worldwide and based on the growth parameters and performance indices, review the possible stock structures and the reliability of growth estimations for dolphinfish. The results support a single-stock hypothesis for dolphinfish in the Kuroshio Current off Taiwan with new estimated VBGF parameters of L∞=149.4cm and K=0.72year−1. Some potentially biased estimates of dolphinfish growth parameters are identified in the worldwide VBGF dataset and are suggested for further investigations. Excluding these estimates, the results indicate at least a five-stock structure in the Pacific and the Atlantic oceans.