The Bonnethead Shark is a small coastal sphyrnid that reaches about 150 cm total length (TL). The life history of this species in the Gulf of Mexico has received considerable attention. In the eastern Gulf of Mexico, female Bonnethead Sharks seldom exceed 130 cm TL, whereas males rarely surpass 110 cm TL. Females generally mature between 80?95 cm TL (or 2?3 years of age) and males mature between 68?85 cm TL (two years of age). Maximum observed ages are 6?7 years or more for females and 5?6 years or more for males, whereas theoretical longevities derived from von Bertalanffy growth curves range from 5?6 years for males and from 10?12 years for females (Parsons 1993a, Carlson and Parsons 1997). Empirical data for populations of this species in the eastern Gulf of Mexico reveal a latitudinal increase in maximum size, size at maturity and offspring size (Parsons 1993, Carlson and Parsons 1997, C.A. Manire pers. comm.).

The Bonnethead Shark is a placental viviparous species that reproduces annually. Its gestation period is one of the shortest known in sharks, lasting approximately 4.5?5 months; litter size averages nine. The periodicity of parturition also varies latitudinally, taking place in mid to late August in Florida Bay (southernmost location), early September in Tampa Bay (middle location) and mid to late September off north-west Florida (northernmost location) (Manire et al. 1995, J. Carlson pers. comm.). Size at birth ranges from an average of 27 cm TL in Florida Bay to 35 cm TL in Tampa Bay (Parsons 1983). Parsons (1993) and Manire et al. (1995) found that mating occurs in November and sperm is stored until ovulation/fertilisation the following March or April. Ongoing tagging studies along the west coast of Florida (R.E. Hueter and C.A. Manire pers. Comm.) indicate that individuals of this species are highly site-attached, with little evidence for long-distance migrations and mixing of populations.

The shallow grass bottoms off Florida?s west coast are documented nursery grounds for this species, which probably utilises similar habitats as nursery areas throughout its range (Hueter and Manire 1994). The Bonnethead Shark's diet off south-west Florida is very homogeneous, dominated by crustaceans, consisting mostly of portunid crabs (Cortés et al. 1996). Stomach contents also show a high incidence of angiosperms, which are likely ingested incidentally to prey capture and denote the benthic feeding habits of this species (Cortés et al. 1996). This species also feeds on cephalopods and fish, but to a much lesser extent. Bonnethead sharks are specialist hunters (Cortés et al. 1996) that appear to have higher daily rations than other species of sharks for which quantitative food consumption data exist (Cortés unpubl.).

Cortés and Parsons (1996) compared the demography of two populations off Florida?s west coast and found short generation times (4?5 years) and high population growth rates (1?28% per year). Recent demographic studies of this species by Cortés (in press) incorporating uncertainty in estimates of vital rates indicate that the bonnethead has very high population growth rates (l) (mean=1.304 yr^-1; 95% confidence interval=1.150?1.165 yr^-1) and short generation times (A) (mean=3.9 years, 95% CI=2.6?4.5 years). Elasticity analysis (which examines the proportional sensitivity of l to a proportional change in a vital rate) also showed that l is most sensitive to juvenile survival and adult survival than to fertility (which includes survival to age^-1). Annual survivorship values used in Cortés (in press) were estimated through five indirect life history methods and ranged from 55?81%. The high l values and elasticity patterns for this species are a result of its ?fast? life history characteristics.