Preliminary Study of Vertebral Growth Rings in the Whale Shark, Rhincodon typus, from the East Coast of South Africa

Growth rings (GR) in vertebral centra of 15 whale sharks, Rhincodon typus, four female (418–750 cm precaudal length), 10 male (422–770 cm), and one of unknown sex (688 cm), were examined using x-radiography. GR counts were made from scanned images and count precision was determined using the average percentage error index (4.19%) and the index of precision D (3.31%). In females, counts ranged from 19 GR (418 cm) to 27 GR (750 cm); in males from 20 GR (670 cm) to 31 GR (770 cm). Three mature males had 20 GR (670 cm), 24 GR (744 cm) and 27 GR (755 cm). A female with 22 GR (445 cm) was adolescent. There was a linear relationship between centrum dorsal diameter and body length, and back-calculated body lengths at number of GR are presented. A linear relationship between body length and number of GR prevented the calculation of von Bertalanffy parameters from either observed or back-calculated values.