New insights into the reproductive biology of the tiger shark Galeocerdo cuvier and no detection of polyandry in Reunion Island, western Indian Ocean

Abstract

The reproductive biology of the tiger shark Galeocerdo cuvier remains poorly documented because it is difficult to obtain data on a sufficient number of mature individuals to conduct appropriate analyses and thus to adequately investigate its population biology. In this study, the reproductive traits of 150 individuals caught during a shark control program in Reunion Island (western Indian Ocean), including five gravid females, were investigated. Specific microsatellite loci were used to investigate the occurrence of polyandry. The total length (TL) of the studied individuals was 130–415cm for males and 175–429cm for females. Sizes at maturity were estimated at 278.5cm for males and 336cm for females. Although the length–weight relationships differed between both sexes (analysis of covariance (ANCOVA): intercept, n=49, F1,45=0.95, P=0.34; slope, n=49, F1,45=8.39, P=0.01), the TL–frequency distributions did not differ significantly. Parturition likely occurs during the warm season, in December–January. No evidence of genetic polyandry was detected, and this supports recently published results. This absence of polyandry in the species likely reflects both a long reproductive cycle and a specific reproductive behaviour related to the oceanic nature of the tiger shark. These results are valuable for improving conservation and management plans for this species.