Preliminary analysis of crocodile shark (Pseudocarcharias kamoharai) distribution and abundance trends in pelagic longline fisheries

Abstract

Crocodile shark (Pseudocarcharias kamoharai) has a broad distribution across the world’s oceans, but is a rare catch in most commercial fisheries. In some geographic areas, crocodile shark is an abundant bycatch of pelagic longline fisheries. Limited crocodile shark biological and fishery information is available to date. We analyzed worldwide pelagic longline fishery observer and research cruise survey data (19502005) to estimate crocodile shark abundance and distribution. Preliminary results suggested the highest crocodile shark catch rates were in the Indian Ocean. Off western Australia, crocodile sharks were one of the most frequently caught species. Results showed that in addition to ocean basin, target species, moon phase, season, bottom depth, gear fishing depth and deployment time significantly affected crocodile shark catches. In each fishery, encounters and catch rates increased with the number of years since exploitation commenced. Pelagic longline fisheries exploited the entire crocodile shark size range, with the species fully selected above 100 cm fork length and most crocodile shark were longer than the reported size at first maturity. The analysis revealed that the crocodile shark sex ratio varied among pelagic fisheries. Japanese Pacific yellowfin and US Pacific tuna fisheries captured more males, whereas US Atlantic swordfish and Japanese southern bluefin fisheries captured more females.