Age and growth of silky shark, Carcharhinus falciformis, from the Eastern Pacific by vertebrae

As a pelagic shark species, the silky shark, Carcharhinus falciformis, in the Eastern Pacific has been overfished in the tuna purse-seine and longline fishery and requires improved assessment to enable planning of recovery actions. The present study examined the life history of 802 silky sharks (67 individuals were sampled, 35 females and 32 males) from the Eastern Pacific. Age was analyzed using sectioned vertebrae, and a multimodel approach was applied to the length-at-age data to fit growth models. Silky sharks ranged in dominant length from 160 to 220 cm total length (L), while ranged in dominant age from 9 to 13 years. Females the longest was 222.58 cm total length, with the oldest estimated at 18 years. Males the longest was 233.47 cm total length, with the oldest estimated at 17 years. The Logistic growth model provided the best fitting growth model. Parameter estimates for females were: asymptotic length (L_∞) = 231.51 cm; growth coefficient (g) = 0.19/a; and length at age 0 (L₀) = 68.89 cm. For males, the parameter estimates were: (L_∞) = 251.96 cm; (g) = 0.15/a; and (L₀) = 68.71 cm. Females matured at (13.50±0.43) years and (207.60±2.43) cm, whereas males mature at (13.42±0.46) years and (200.67±3.60) cm. The growth parameters and late ages of sexual maturation for silky sharks in the Eastern Pacific suggest a significant risk from fisheries exploitation without careful population management.