Growth of juvenile tarpon in Puerto Rican Estuaries

Daily growth increments in otoliths of juvenile Megalops atlanticus, were validated by injection of oxytetracycline hydrochloride (OTC) while in the mangrove zone of Boqueron Bay, Puerto Rico. Peritoneal and intra-muscular injection of OTC at 100 mg kg −1 doses were successful in marking otoliths of juvenile tarpon which ranged from 39-133 mm in standard length (SL). The growth rate estimated from SL-age regression, suggested a growth rate of 0.92±0.03 (s.e.) mm day −1 . At estuarine arrival, tarpon leptocephali were estimated to have a mean age of 33.7±0.3 d (n=182), with most larvae being in their second stage of metamorphosis. The young age at arrival supports the hypothesis that tarpon spawning grounds occur relatively close to the Puerto Rican shore. Back-calculated hatching dates from tarpon otolith microstructure suggests a long spawning season in Puerto Rico with two annual peaks, one occurring in springtime (March-May) and another in late summer (July-September).