950 



Fishery Bulletin 97(4). 1999 





•Id (1Se7) 

 TMi S&idy. Qulwd aod Holt (1958) HMhod 

 IMofittily LangSi Fr«qu«ncy Modes. 6 y««n 

 OTC. 4 ndlvWuaO 



10 



15 



20 



25 



30 



35 



Figure 3 



The von Bertalanffy growth curves from tag-recapture analysis was estimated with the Gulland and Holt ( 1959) 

 model and the von Bertalanffy growth curve estimated from vertebral analysis (Branstetter et al. 1987). The 

 solid lines represent the individual monthly length-frequency mode data from six year classes (1988-93). The 

 initial points of the line are set by the size in June of the birth year The solid lines are actual growth of four 

 individual OTC-injected recaptured sharks at liberty over 0.9 yr. The length at tagging was used to obtain the 

 initial age estimate to set the point on the graph. 



eluding environmental conditions and prey availabil- 

 ity. Our data show that that the majority of neonatal 

 tiger sharks remain in the nursery area from birth 

 until about 120-150 cm FL or 1.5—2 years of age. ^ It 

 is known that tiger sharks frequently migrate into 

 and out of the Gulf of Mexico (Kohler et al., in press). 

 It is doubtful, with the migratory nature of this spe- 

 cies and mixing between these areas, that growth 

 rate differences in these groups are biologically sig- 

 nificant past perhaps the first three years of life. 



The longevity of the tiger shark is difficult to esti- 

 mate. The NMFS tagging program has received data 

 on five tiger sharks at liberty for 6 to 11 years. The 

 oldest of these fish would have been 3+ years at tag- 

 ging (185 cm FL, estimated), on the basis of the 

 Gulland and Holt (1959) growth curve and, there- 

 fore, 14-1- years at recapture (325 cm FL, measured). 

 Branstetter et al.'s ( 1987 ) oldest aged tiger shark was 

 16 years of age. Our longevity estimate, based on a 

 7 half-life criterion, indicated that tiger sharks may 

 live to be at least 27 years of age. Branstetter et al. 

 (1987) estimated maximum age at anywhere from 

 20-37 years based on L . for their various VBGF 

 curves and rate of growth of large individuals. 



Based on revised growth estimates presented in 

 this study, estimated maximum age for this species 

 is 27 years. Age at maturity, estimated from tag-re- 

 capture data from this study and size at maturity 

 estimates from Branstetter et al. (1987), is seven 



years suggesting that females mature at 25% of their 

 maximum age and may reproduce 10 times based on 

 a two-year reproductive cycle. 



Overall, the tiger shark is similar to other large 

 carcharhinids in that it grows slowly and has a rela- 

 tively long life, although it matures earlier than many 

 other species in the northwest Atlantic (C. leucas 14— 

 18 years, Branstetter and Stiles, 1987; C. plumbeus 

 15-30 years; Casey and Natanson, 1992, Sminkey 

 and Musick, 1995; C. obscurus 19-20 years; Natan- 

 son, 1994; C. falciformis 6.5-12 years, Branstetter, 

 1987c, Bonfil et al., 1993). Branstetter (1987b) dis- 

 cussed the various life strategies of sharks on the 

 basis of their k values. He suggested that tiger 

 sharks, with k values from 0.11 to 0.16, fit into an 

 intermediate category between slow growth species 

 (/?=0.05-0.10) such as C. plumbeus, C. obscurus, Neg- 

 aprion brevirostris, and Sphyrna lewini and fast growth 

 species (/f>0.2) such as C. limbatus, C. brevipinna, 

 Rhizoprionodon terraenovae, and Prionace glauca. 

 Other sharks in the intermediate group include C. 

 acronotus and C. falciformis according to Branstetter 

 ( 1987b). The tiger shark reaches maturity at a lower 

 percent {257c) of its total age than do other 

 carcharhinids for which this parameter has been es- 

 timated (S. lewini 33-50^^r, Branstetter, 1987c). This 

 finding suggests that the tiger shark has a longer re- 

 productive life span and possibly a greater reproduc- 

 tive potential than other carcharhinids. 



