Age, growth and demography of the silky shark Carcharhinus falciformis from the southwestern Atlantic

The silky shark Carcharhinus falciformis is considered one of the least productive pelagic shark species. The estimation of growth and demographic parameters presented here is fundamental to a sound knowledge of population status of the species in the Atlantic Ocean. Data was collected through an onboard observer program of the Brazilian chartered pelagic longline fishing fleet that operates in the Equatorial Southwestern Atlantic. Vertebral analysis produced the von Bertalanffy growth parameters for pooled sexes L-infinity = 283.05 cm; k = 0.0987 yr(-1) and t(0) = -3.47 yr. Males reached sexual maturity at 8.6 yr and females at 9.9 yr. Longevity was estimated at 27.2 yr. Age structure analysis indicated that 80.5% of the catch was composed of juveniles, with recruitment to the fishery from the first year of life (age 1+). These biological parameters are responsible for the species' low resistance to fishing pressure, and our demographic analysis (Leslie Matrix) shows an annual population decline of 12.7% yr(-1) under the current fishing scenario for the period analyzed. Therefore, conservation measures must be enacted to reestablish the population of silky sharks to safe levels for the maintenance of this species in the South Atlantic.

Automated summary

The silky shark is considered one of the least productive pelagic shark species, and understanding its growth and demographic parameters is crucial for assessing its population status in the Atlantic Ocean. Research revealed that the species has low resistance to fishing pressure, with a population decline rate of 12.7% annually under current fishing practices. Conservation measures are necessary to restore the silky shark population in the South Atlantic.