Determining toothfish otolith structure using oxytetracycline
at South Georgia – a preliminary report

A tagging programme for Patagonian toothfish (Dissostichus eleginoides) was initiated at South Georgia and Shag Rocks early in 2000. A total of 2486 have been tagged and released during trawl surveys, experimental pot fishing and longline fishing. Some of the fish tagged on longliners in 2002 were injected with oxytetracycline (OTC) to mark the otoliths for age validation purposes. The otoliths of some of these chemically marked recaptures of the 2003 season were examined and the preliminary results are presented here. Two fish marked with strontium-chloride (SrCl2) during the 2002 trawl survey were also recaptured. From recaptures of chemically marked fish our study seems to indicate that the dosages used for the injection of both OTC and SrCl2 did not impact negatively on their survival rate.