Updated size composition of shortfin mako shark caught by the Taiwanese tuna longline fishery in the North Pacific Ocean
There are two types of Taiwanese tuna longline vessels, namely the large-scale tuna longline vessels (LTLL, ≧100 GRT) and the small-scale tuna longline vessels (STLL, ＜100 GRT). In the present study, the size data of the shortfin mako shark caught by these two fisheries are presented. All size data recorded in other measurements were converted to pre-caudal length (PCL) by using the converting equations available. The size of shortfin mako caught by the Taiwanese STLL from 1989-2019 in the North Pacific ranged from 61 to 338 cm PCL for females (n = 116,281), and 60–262 cm PCL for males (n = 108,505). The sizes of 11,173 individuals (sexes combined) recorded in the logbook of LTLL from 2005-2019 ranged from 61 to 303 cm PCL. Two modes (mostly 100 and 150 cm PCL) were observed in the size distribution of shortfin mako shark caught by the STLL in the North Pacific Ocean. This also implied that the catches comprised mostly immature fish (female < 228, male < 172 cm PCL). The capture of high proportion of immature sharks may have serious impact on the sustainability of the fishery.