Long-term retention and detection of oxytetracycline marks applied to hatchery-reared larval striped bass, Morone saxatilis
Hatchery-reared larval striped bass, Morone saxatilis, destined for stocking in the Savannah River, Georgia, were immersed in oxytetracycline (OTC) to mark bony structures for later identification. Approximately 170 000 of these fish were raised to larger sizes and tagged with micromagnetic coded-wire tags (CWT). Recaptures of OTC-marked (OTC only) and marked and tagged (OTC and CWT) fish allowed us to determine retention of the OTC mark in otoliths to 3 years of age and to evaluate reader ability to detect those marks. The estimated retention rate was 80.2% for the first year, with no detectable change in additional years. Detection of OTC was age independent and estimated at 72.6% when one otolith was examined versus 92.5% when both otoliths were examined. Only 74.2% (retention x detection) of recaptures in this study would have been correctly identified as stocked fish if OTC alone was used as the marking method.