Stock Status Estimating of 5 Shark Species in the Waters Around Taiwan Using a Length-Based Bayesian Biomass Estimation (LBB) Method

Peilong Ju,Yu Zhao,Jiamei Xiao,Mingru Chen,Yongjun Tian,Shengyun Yang

doi:10.3389/fmars.2020.00632

Abstract

Five shark stocks in the waters around Taiwan were assessed using the LBB method, addressing the present gap. Among them, only one filter-feeding shark, megamouth shark Megachasma pelagios, qualified as having a healthy status. Of the remaining filter-feeding shark, whale shark Rhincodon typus, was seriously overexploited, possibly even collapsed, spadenose shark Scoliodon macrorhynchos, and other two large sharks (dusky shark Carcharhinus obscurus and silky shark Carcharhinus falciformis) were also overexploited. These stock status estimates for the five shark species using the LBB method were consistent with international agreements such as IUCN, CITES and CMS.

Highlights

Sharks and their relatives are more vulnerable to overfishing due to their conservative life-history traits, such as slow growth, old ages of reproduction, long gestation periods, and high levels of maternal investment (Cortés, 2000; Dulvy et al, 2014; Adams et al, 2018; Booth et al, 2019)
The increasing global demand and high market value for shark fins exacerbates the depletion of low-productivity sharks (Cortés, 2000; Booth et al, 2019), which is more serious in Chinese waters (Eriksson and Clarke, 2015)
Sharks have been listed in international agreements to regulate fishing and trade (Booth et al, 2019), such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

Summary

Introduction

Sharks and their relatives (chondrichthyans, “sharks”) are more vulnerable to overfishing due to their conservative life-history traits, such as slow growth, old ages of reproduction, long gestation periods, and high levels of maternal investment (Cortés, 2000; Dulvy et al, 2014; Adams et al, 2018; Booth et al, 2019). The increasing global demand and high market value for shark fins exacerbates the depletion of low-productivity sharks (Cortés, 2000; Booth et al, 2019), which is more serious in Chinese waters (Eriksson and Clarke, 2015). It is estimated that a quarter of shark species are threatened with extinction (Dulvy et al, 2014)

Methods

Results

Conclusion