Distribution, biology and fisheries importance of the pencil shark, Hypogaleus hyugaensis (Elasmobranchii : Triakidae), in the waters off south-western Australia

Abstract

Distribution, biology and fishery importance of the pencil shark, Hypogaleus hyugaensis, off Western Australia was investigated using data from fishery observers and commercial fisheries landings. Observers collected data from 1823 gillnet sets and examined 516 specimens. The sex ratio was even and the majority of animals were greater than 84 cm fork length (FL). The size at maturity for males was estimated to be 82 cm FL, and for females to be 82-90 cm FL. Females have a two-year reproductive cycle. Ovulation occurs from March to May, with parturition probably occurring after a gestation period of less than 12 months. The size at birth was estimated to be 30-32 cm FL. Litter size ranged from 2 to 15, with a mean of 9.6. Pelagic teleosts and squid dominated the diet. Highest catch rates based on observer data occurred at depths between 50 and 80 m. Landings data indicate that H. hyugaensis make up approximately 0.5% of the shark catch in the fisheries off Western Australia. Steady catch rates since 1989 suggests that the fishery has had no impact on the population. Landings data and observer catch rate data show different patterns of seasonal and geographic distribution. However, landings data are probably unrepresentative of actual catches in the fisheries due to problems with identification and discarding.