Estimate of Live Release and Dead Discards of the Shortfin Mako Shark Caught by the Chines Taipei Longline Fishery in the North Atlantic Ocean

Chinese Taipei longline fisheries have ban retention of shortfin mako shark (Isurus oxyrinchus) in the North Atlantic Ocean since 2018. However, detailed information of the live release and dead discards of shortfin mako is still unknown. Although Chinese Taipei observer program started in 2004, the live release and dead discard without retention data were only available from 2017 to 2020. The nominal CPUE of shortfin mako obtained from observer’s records from 2007 to 2020 were standardized using a Delta Lognormal model. The total shortfin mako shark catch in number of the Chinese Taipei longline fleets in the North Atlantic was estimated by a multiplication of standardized CPUE and total effort in the logbook of the Chinese Taipei longline fleets. The total live release and dead discard of shortfin mako caught by the Chinese Taipei longline fleets were estimated by the live release and dead discard ratio obtained from observer’s records multiplying the estimated annual catch in number. These numbers multiplied by the mean weight in catch can obtain the total catch in weight of shortfin mako ranged from 6 to 32 tons including live release of 2-10 tons and dead discard of 4-22 tons for the Chinese Taipei fleets in the North Atlantic in 2018-2021.