Catch and effort standardization for Taiwanese swordtip squid Uroteuthis edulis fisheries in the southern East China Sea

Abstract

The swordtip squid Uroteuthis edulis is a neritic squid species that is widely distributed within the coastal waters of subtropical and tropical Indo-western Pacific regions. This squid is a commercially important species throughout its distribution range and plays a critical role in marine ecosystems. Stock assessments of the squid in the East China Sea (ECS) are scarce, although it is crucial information for the sustainability of the squid and relevant fisheries. The squid was harvested by various fisheries in the southern ECS, which could restrict methods for catch-effort standardization. In this study, catch-effort data of Taiwanese swordtip squid fisheries in the southern ECS between 2002 and 2013 were standardized by the relative catch per unit effort (CPUE) comparison method to examine annual abundance variations of the squid. The results revealed that the standardized CPUE of squid fisheries was lower than the nominal CPUE series. The standardized CPUE of the squid from Taiwanese torch-light vessels revealed slight variability between 2003 and 2009 and great inter-annual variations between 2010 and 2013. The effects of varying parameters on the relative power factor estimates of the vessels are examined and discussed. This study provides an alternative approach of CPUE standardization for swordtip squid fisheries in the southern ECS and a relative abundance index of the squid, which could support further stock assessment and management of fisheries in the region.