AGE AND GROWTH OF THE BONNETHEAD SHARK, SPHYRNA-TIBURO, FROM NORTHWEST FLORIDA, WITH COMMENTS ON CLINAL VARIATION

Age and growth rates of the bonnethead shark, Sphyrna tiburo, from nor thwest Florida were estimated from vertebrae collected between October 1992 and October 1995. The von Bertalanffy growth equation was fit to male and female vertebral age data. Initial growth was rapid (approxi mate to 200 mm TL) for both sexes from age 0-1. At age 2 growth slowed for males but continued for females. Similar to many species of shark s, females grew slower than males (K = 0.28 and K = 0.69, respectively ) but attained a larger maximum size (L-infinity = 1226 and L-infinity = 897). Maximum age was estimated in males and females to be 8+ and 1 2+ years, respectively. Growth of young-of-year sharks was 21 to 30 mm TL per month determined by three different methods. A comparison of a ge and growth estimates from populations at more southerly latitudes s uggest that clinal variation in total length may be evident among bonn ethead sharks in the Gulf of Mexico with females reaching larger sizes in northern areas as compared to south Florida.