Size and maturity status of the whale shark (Rhincodon typus) at Ningaloo Reef in Western Australia

Norman, B.M. and Stevens, J.D. (2007) Size and maturity status of the whale shark (Rhincodon typus) at Ningaloo Reef in Western Australia. Fisheries Research, 84 (1). pp. 81-86.

Abstract

Between 1995 and 1997, 360 observations of whale sharks at Ningaloo Reef revealed that approximately 85% were males (4-12 m TL). Based on the external morphology of claspers, all males <7 m TL were immature. Only 9.3% of males between 7 and 8 m TL were found to be mature, compared to 36.6% of those between 8 and 9 m TL. All but one of the 79 male whale sharks >9 m were considered mature. A logistic equation fitted to the percentage of mature males in each size class predicted a length at first maturity (L50) of ∼8.0 m TL, while 95% (L95) of males were mature by ∼9.0 m TL. Female whale sharks at Ningaloo Reef during this study were generally smaller and ranged in length from 4 to 8 m TL. The small size and general absence of female whale sharks from Ningaloo Reef suggest that the region may be important for feeding rather than breeding.