FISHERY BULLETIN: VOL. 85, NO. 2 



400 



350 

 300 



? 250 



X 200 



LLI 



^ 150 



100 



50 



Galeocerdo cuvieri 



log wt. = 3.24(log TL) - 5.85 

 wt. = 1.41 X lO'^TL^'^") 



n = 120 



r = .944 



50 100 150 200 250 300 350 400 

 TOTAL LENGTH (cm) 



Figure 6.— Weight/length relationship for Atlantic and Gulf of Mexico Galeocerdo cuvieri, 



sexes combined. 



animals matured at 310-320 cm, linear growth 

 slowed from 15 cm/year to <10 cm/year, and weights 

 increased dramatically. 



DISCUSSION 



An isometric relationship between centrum growth 

 and length has been noted for many shark genera 

 (Cailliet et al. 1983; Gruber and Stout 1983; Bran- 

 stetter and McEachran 1986). The slight curvilinear 

 relationship between centrum growth and length 

 noted for Galeocerdo cuvieri suggested there were 

 two distinct growth stanzas. A similar relationship 

 was also noted for hums oxyrinchus (Pratt and 

 Casey 1983). The point of inflection in the curve is 

 generally at the length corresponding to the onset 

 of maturity, a decreased linear growth rate and an 

 increased weight gain rate. Apparently, centrum 

 growth is correlated to the structural support neces- 

 sary for length increases, but an increasing rate of 

 weight gain does not require additional strengthen- 

 ing of the vertebral column. 



Marginal increment analysis of annulus periodicity 

 demonstrated that one growth band, consisting of 



one calcified opaque zone and one less calcified 

 translucent zone, formed annually. A similar period- 

 icity for growth bands or annuli has been verified 

 for several shark genera (Gruber and Stout 1983; 

 Cailliet et al. 1986; Branstetter and McEachran 

 1986) and validated using tetracycline injected 

 Negaprion brevirostris (Gruber and Stout 1983), 

 Triakis semifasciatus (Smith 1984), Rhizoprionodon 

 terraenovae, and Carcharhinus plumbeus (Bran- 

 stetter 1987a). In contrast, Parker and Stott (1965) 

 and Pratt and Casey (1983) provided evidence that 

 lamnoids produce two band pairs per year, and 

 Natanson (1984) could find no regular periodicity in 

 centrum bands of Squatina californica. 



Our estimates indicated the tiger shark doubles 

 in length the first year of life. This is supported by 

 growth of a full-term embryo (69 cm) placed in an 

 aquarium by Clark and von Schmidt (1965) on 21 

 May, where it survived 12 weeks growing to 89 cm. 



Rapid linear growth for juvenile tiger sharks may 

 be necessary for adequate cohort survival. With a 

 13-16 mo gestation period (Clark and von Schmidt 

 1965) and a mating season which occurs before full- 

 term females have pupped, the female reproductive 



276 



