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

Jones Santander-Neto*, Rodrigo Barreto, Francisco M. Santana, Rosangela P. T. Lessa

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ABSTRACT: 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 infer about 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 = 283.05 cm; k = 0.0987 yr-1 and t0 = –3.47 years. Males reached sexual maturity at 8.6 yr, and females at 9.9 yr. Longevity was estimated at 27.2 yr. Age-structure indicated that 80.5% of the sample comprised juveniles with recruitment to the fishery from the first year of life (age 1+). Through demographic analysis (Leslie Matrix), the population of C. falciformis showed an annual decline of 11% in the current fishing scenario due to its low resilience conferred by its biological parameters. Therefore, conservation measures must be enhanced to reestablishing population biomass to safe levels and for the maintenance of this species in the South Atlantic.