Age and growth of the whale shark (Rhincodon typus) in the north-western Pacific

Abstract

This study estimated age and growth of the largest extant fish, the whale shark (Rhincodon typus) by counting vertebral band pairs from 92 specimens comprising 43 males (2.68–9.88 m total length [TL]), 30 females (1.60–7.02 m TL), and 19 unsexed individuals (2.83–6.67 m TL) taken by Taiwanese commercial fisheries during 2001–06. Growth band pairs up to 25 and 42 were counted for a 6.38-m TL female and a 9.88-m TL male, respectively. Using marginal increment ratio and centrum edge analysis, band pairs were postulated to be formed twice a year. The two-parameter von Bertalanffy growth function provided the best fit without significant differences between sexes. Growth parameters were calculated for both sexes as L∞ = 16.80 m TL, k = 0.037 year–1; annual band pair formation would modify these parameters to L∞ = 15.34 m TL, k = 0.021 year–1. Using data reported in another study for 50% size at maturity for males (8.1 m TL), and the largest immature and smallest mature females (8.7 and 9.6 m TL, respectively) in the Indo-Pacific, these TLs converted to ages at maturity of 17 years for males and 19–22 years for females. The longevity was calculated to be 80.4 years.