Growth Rates in The Nurse Shark, Ginglymostoma cirratum

Growth rates determined from recapture of free-ranging nurse sharks (Ginglymostoma cirratum) averaged 13.1 ? 9.5 cm/yr and 2.3 ? 1.3 kg/yr based upon recapture of 44 tagged animals (28.9% recovery) with an average at-large interval of 247 d (range: 5-876 d), and an average size at tagging of 126.6 cm TL and 9.8 kg body mass. Growth measurements on three captively maintained nurse sharks averaged over a 3 yr period, resulted in growth rates that were slightly faster (19.1 ? 4.9 cm/yr and 4.0 ? 1.7 kg/yr), but not significantly different. The captive study, however, revealed that growth rates decreased as the age of the animals increased (from approx. 3-6 yr of age). Estimation of growth in the captive population, at times when animals were of similar size as those tagged in the wild, resulted in growth rates that were considerably closer (13.8 ? 2.3 cm/yr and 3.7 ? 2.2 kg/yr). Percent changes in total length for free-ranging nurse sharks and captive nurse sharks of similar size were 11.4%/yr and 11.3%/yr, respectively, while percent changes in body mass averaged 32.7%/yr for recaptured animals compared with 31.6%/yr for comparable sized nurse sharks in captivity.