Distribution and reproductive biology of the sandbar shark, Carcharhinus plumbeus (Nardo), in Western Australian waters

Abstract

In total, 7497 sandbar sharks, Carcharhinus plumbeus (Nardo, 1827), were collected between May 2000 and June 2003 from commercial fishers and during fishery-independent research cruises in coastal Western Australian waters. Maximum observed lengths were 165 and 166 cm fork length (FL) for males and females respectively. The lengths at which 50% of sharks were mature were 126.9 and 135.9 cm FL for males and females respectively. Juvenile sharks tended to occur in temperate waters, whereas mature-sized sharks predominantly occurred in tropical waters. Unlike other regions, juveniles were found in offshore continental shelf waters rather than in shallow waters of estuaries and marine embayments. Results indicated a biennial reproductive periodicity. Mating occurred during summer and autumn, and parturition took place after a 12-month gestation. Pups were born at 40 to 45 cm FL throughout most of the species’ Western Australian range. The majority of neonates were caught at temperate latitudes. Litter sizes varied between 4 and 10, with a mean of 6.5. There was a weak but statistically significant increase in litter size with maternal length. Mean embryonic sex ratio of females to males differed significantly from a one-to-one ratio.