Size frequency, dispersal distances and variable growth rates of young sharks in a multi‐species aggregation

Abstract : During a mark–recapture survey from November 2014 until April 2017, 333 neonatal and juve- nile blacktip reef sharks Carcharhinus melanopterus and 302 neonatal and juvenile sicklefin lemon sharks Negaprion acutidens were tagged and measured at the uninhabited and isolated St. Joseph Atoll (Republic of Seychelles). Both species demonstrated seasonal reproductive syn- chronicity and relatively large sizes at birth. Despite the extended times at liberty > 2.5 years, the majority of recaptures were found in close proximity to the initial tagging location (< 500 m). Annual growth rates of C. melanopterus (n = 24) and N. acutidens (n = 62) ranged from 6.6 to 31.7 cm year −1 (mean ± SE; 16.2 ± 1.2 cm year −1 ) and 0.2 to 32.2 cm year −1 (11.8 ± 1 cm year −1 ), respectively and are to date the most variable ever recorded in wild juve- nile sharks. High abundances of both species coupled with long-term and repeated recaptures are indicative of a habitat where juveniles can reside for their first years of life. However, large variability in annual growth rates in both species may suggest high intra and interspecific com- petition induced by a possibly resource limited, isolated habitat.