Updated standardized CPUE and historical catch estimate of the shortfin mako shark caught by Taiwanese large-scale tuna longline fishery in the North Pacific Ocean

Abstract

In the present study, the shortfin mako shark catch and effort data from the logbook records of the Taiwanese large-scale tuna longline fishing vessels operating in the North Pacific Ocean from 2005-2019 were analyzed. Due to large percentage of zero shortfin mako shark catch, the catch per unit effort (CPUE) of shortfin mako shark, as number of fish caught per 1,000 hooks, was standardized using a zero inflated negative binomial model. Both nominal and standardized CPUE of shortfin mako shark showed an interannual fluctuation with two peaks (2013, 2014 and 2018, 2019). Estimated shortfin mako shark catch in weight from the Taiwanese large-scale tuna longline fishery ranged from 0 metric tons (MT) in 1973 to 156 MT in 2015, and it decreased thereafter and increased again to 142 MT in 2019.