A COMPARISON OF THE AGE AND GROWTH OF 



THE TIGER SHARK, GALEOCERDO CUVIERI, FROM OFF VIRGINIA 



AND FROM THE NORTHWESTERN GULF OF MEXICO' 



Steven Branstetter,^ J. A. Musick,^ and J. A. Colvocoresses^ 



ABSTRACT 



Lengths at age and growth rates for the tiger shark, Galeocerdo cuvieri, in the northwestern Alantic 

 and Gulf of Mexico were estimated from bands formed seasonally in the vertebral centra. The tiger shark 

 grows rapidly compared with many other shark species. Growth rates for Gulf of Mexico juveniles were 

 faster than for Atlantic juveniles. This produced significantly different {P < 0.01) estimates of the 

 parameters of von Bertalanffy curves for the two regional samples. With sexes combined, parameter 



estimates for the Gulf of Mexico sample were L„ = 388 cm TL, K = 0.184, t^ 



1.13 years; for the 



Atlantic sample they were L„ = 440 cm TL, K = 0.107, t^ = -2.35 years. Males mature at approx- 

 imately 310 cm TL, females at 315-320 cm TL, but the regional differences in juvenile grow^th rates 

 result in different ages at maturity. In the Gulf of Mexico, males mature in 7 years, females in 8 years; 

 in the Atlantic, males and females both mature in approximately 10 years. The largest male and female 

 examined (381 cm TL) were 15 and 16 years of age. 



The tiger shark, Galeocerdo cuvieri, is cosmopolitan 

 in warm-temperate and tropical coastal and oceanic 

 waters of the western North Atlantic (Castro 1983). 

 It is usually found alone or in small groups of three 

 to six individuals distributed rather homogeneous- 

 ly over most bottom types (Springer 1963). Because 

 of its large size, it is one of the most frequent en- 

 tries in recreational fishing tournaments, and it 

 occurs regularly, but in low numbers, in longline 

 catches (Clark and von Schmidt 1965; Dodrill 1977; 

 Branstetter 1981, 1986). Along the U.S. Atlantic 

 coast, the tiger shark occurs year-round off Florida, 

 migrates as far north as Cape Cod in summer (Casey 

 1964), and returns to more southerly latitudes in fall 

 (Musick et al. 1985). In the Gulf of Mexico, the 

 species occurs in coastal waters from spring through 

 fall, and in deeper continental shelf and offshore 

 regions year-round (Branstetter 1981, 1986). 



The low catch rates and semisolitary nature of the 

 tiger shark have hindered a comprehensive study 

 of its biology. The tiger shark is both a scavenger 

 (Gudger 1949; Clark and von Schmidt 1965) and 

 euryphagous predator (Bass et al. 1975; Dodrill and 

 Gilmore 1978). Information on the reproductive 

 biology of the tiger shark must be gleaned from scat- 



'Contribution No. 1365 of the Virginia Institute of Marine 

 Sciences. 



^Department of Wildlife and Fisheries Sciences, Texas A&M 

 University, College Station, TX 77843. 



'Virginia Institute of Marine Sciences, Gloucester Point, VA 

 23062. 



tered observations on pregnant females taken in the 

 Indo-West Pacific and Indian Ocean (Kauffman 

 1950; Bass et al. 1975) and in the northwestern 

 Atlantic (Clark and von Schmidt 1965; Dodrill 1977; 

 Branstetter 1981). Age and growth rates for the 

 tiger shark have not been reported. 



Alternating opaque (calcified) and translucent (less 

 calcified) bands form in the vertebral centra of many 

 elasmobranchs during growth (Radtke and Cailliet 

 1984), and if a regular periodicity can be demon- 

 strated for the formation of these bands through- 

 out the life of the animal (Beamish and McFarlane 

 1983), they can be used to assess ages for individuals 

 in the sample and to estimate growth rates for the 

 population. Using these bands, age and growth data 

 for collections of tiger sharks from Virginia and the 

 northwestern Gulf of Mexico were developed, com- 

 pared, and integrated with known life history char- 

 acteristics. 



METHODS AND MATERIALS 



Tiger sharks were examined from research and 

 commercial longline catches and from recreational 

 fishing tournaments. The Atlantic sample consisted 

 of 27 specimens taken during 1983 and 1984 sum- 

 mer tournaments, and 42 specimens collected in 

 May through October on longlines fished in con- 

 tinental shelf waters (primarily <40 m) within a 50 

 km radius of the mouth of Chesapeake Bay from 

 1977 to 1983. The Gulf of Mexico sample consisted 



Manuscript accepted February 1987. 

 FISHERY BULLETIN: VOL. 85, NO. 2, 1987. 



269 



