Preliminary study on the use of the vertebrae centrum in the age determination of skates in Crozet and Kerguelen waters

Skates are commonly captured as bycatch in the Patagonian toothfish (Dissostichus eleginoides) fishery occurring between 500-2000 m in Crozet and Kerguelen waters. Age data is then important to perform fishery assessment and management. However, previous age estimation on closely related species has proved to be difficult due to low calcification found in deep-sea species. Consequently, different ageing techniques were applied on vertebrae of Amblyraja taaf (n=34), Bathyraja eatonii (n=27) and Bathyraja irrasa (n=34). Both corpus calcareum and centrum structures were observed to perform growth band counting. Although no band have been exploitable using the conventional method based on the observation of the corpus calcareum, most of the samples have been analyzed through the centrum observation. Results suggest that centrum observation could provide a better and efficient approach to ageing deep-sea skates and should be further investigating.