Abstract

Juvenile tarpon were found in both fresh water channels and brackish mangrove back waters of an impoundment in Boquerón, Puerto Rico. A pilot capture and recapture experiment along with in situ injection of Oxytetracycline hydrochloride (OTC) at 100 mg/kg provided estimates of growth, age and residency time in these areas. Juvenile tarpon were found to colonize the backwater areas from June to January, reside several months and grow 1.1 % of their standard lengths per day.\Oxytetracycline HCL injection both peritoneal and intra-muscular were successful in marking otoliths from juvenile tarpon (40 to 100 mm SL). Difficulties with daily ring readings of tarpon larger than 100 mm SL were encountered and believed to be caused by an irregular growth of the sagittea. Significant linear relationship was found between the standard length and estimated age of 28 and 26 juveniles from each sampling area. Although environmental parameters such as temperature, dissolved oxygen and salinity were quite dissimilar between these two areas studied, no significant difference was found between the condition factors or growth rates of tarpon populations from both sites (1992 and 1993).\Short term use of external tags (mini-spaghetti and dangling tags) in the backwater pools yielded high retention and recovery rates (43% and 74% respectively) over a period of 140 days. Growth rates measured from recaptured tarpon were below those calculated from daily ring readings. This discrepancy is believed to be caused by stresses associated with handling during tagging or OTC injection. The maximum observed size and residency for tarpon in the backwater areas was 56 days and180 mm SL.

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