The use of oxytetracycline as a marker for juvenile cod ( Gadus morhua L.)

• Published in: Journal of Fish Biology
• Main Authors: Nordeide, J. T., Holm, J. C., Otterå, H., Blom, G., Borge, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1992
• Subjects: Gadus morhua
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1992.tb03167.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1992.tb03167.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1992.tb03167.x

We examine aspects of marking large numbers of juvenile cod ( Gadus morhua L.) by oxytetracycline (OTC) for cod enhancement experiments. Reared cod were given OTC through the feed and released in a fjord. Control groups were kept in net pens. A total of 93% of the cod became marked. The size of the cod and the percentage marked were inversely related. The location of the mark within each vertebra gradually changed towards the centre as the cod grew and new bone tissue was added. The percentage of marked cod in the control group did not decrease during a period of almost 3 years after marking, although the intensity of the mark gradually declined. After release, we found no indication that the OTC affected growth or survival of the cod. Cod marked as O‐group could be distinguished from cod marked as 2‐group, from the position of the mark within the vertebra.