Using bomb radiocarbon analyses to validate age and growth estimates for the tiger shark, Galeocerdo cuvier, in the western North Atlantic

Refined and validated age and growth determinations are necessary for a proper understanding of tiger shark (Galeocerdo cuvier) life history characteristics in the western North Atlantic (WNA). Age and growth estimates were derived from band counts of 238-sectioned vertebral centra. Bomb radiocarbon analysis of ten band pairs extracted from four vertebral sections suggested that band pairs are deposited annually up to age 20. Males and females were aged to 20 and 22 years, respectively, although longevity estimates predict maximum ages of 27 and 29 years, respectively. Two- and three-parameter von Bertalanffy and Gompertz growth functions fit to length at age data demonstrated that growth rates were similar for males and females up to around 200 cm fork length (FL) after which male growth slowed. Both sexes appear to reach maturity at age 10. The two-parameter von Bertalanffy growth function provided the best biological fit to length at age data generating parameter estimates of: L-infinity = 330 cm FL, k = 0.131 for males and L-infinity = 347 cm FL, k = 0.124 for females, with L-0 set at 62 cm FL. This study provides a rigorous description of tiger shark age and growth in the WNA and further demonstrates the utility of bomb radiocarbon as an age validation tool for elasmobranch fish.