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Age Assessment of the Lemon Shark, Negaprion brevirostris, Using Tetracycline Validated Vertebral Centra
Craig A. Brown and Samuel H. Gruber
Vol. 1988, No. 3 (Aug. 3, 1988), pp. 747-753
Stable URL: http://www.jstor.org/stable/1445397
Page Count: 7
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Vertebral centra were removed from 55 tag-recaptured lemon sharks, Negaprion brevirostris, that had been injected intramuscularly with tetracycline hydrochloride at a dosage level of 12.5 mg/kg at the time of release. Tetracycline deposited at sites of active calcification on the vertebral centra served as a fluorescent marker along the periphery of each centrum at the time of injection. Thin growth zones, or circuli, were observed in ground and stained sections. A lunar periodicity of approx. 29 d was validated for circulus deposition. Precision of circulus counts was evaluated, with an index of average percent error of 3.4% for a single reader. Age estimates were then obtained using circulus counts for a total of 110 sharks, with a plot of precaudal length against estimated age for both sexes fitting a von Bertalanffy growth curve with the parameters L∞=317.65, k = 0.057, and t0=-2.302. The predicted age at maturity for males is 11.6 yr and for females is 12.7 yr. These results show that this species is slow growing and long-lived.