Age and Growth of the Bull Shark,Carcharhinus leucas, from Southern Gulf of Mexico

Age and growth of bull shark, Carcharhinus leucas, was investigated in the southern Gulf of Mexico (Veracruz and Campeche, Mexico) from December 1993 through June 1997. Ninety-five specimens were obtained from commercial fishery catches, and vertebrae were examined from 20 males, 61 females and 14 individuals unidentified to sex. Vertebrae were examined using five different techniques to enhance the visibility of growth rings: i) alizarin red stain, ii) crystal violet stain, iii) X-ray, iv) silver nitrate stain, and v) without staining. Verification of temporal growth ring formation was done by the indirect method of marginal increment analysis. An isometric relationship was found between growth and length of centrum, is described by a linear equation. Age-at-maturity was 10 years (204 cm total length, TL) for females and 9-10 years (190)(191)(192)(193)(194)(195)(196)(197)(198)(199)(200) for males. The oldest female was 28 (256.0 cm TL), and the oldest male was 23 (243.0 cm TL). The von Bertalanffy growth parameters were estimated for the species (L = 256.4 cm TL, k = 0.1397 per year and t o = -1.935), for males (L = 248.4 cm TL, k = 0.1692 per year and t o = -1.03), and for females (L = 262.1 cm TL, k = 0.1235 per year and t o = -2.44). Sexual differences for each particular growth curve were found, L being the parameter that showed the greatest difference between males and females; females attain a larger size.