Year: 2007
Type: report
Abstract: This report provides the presentations, discussions and conclusions from the ICCAT bluefin \ntuna workshop for direct ageing held in Santander, Spain, in April 2006. The report \nsummarizes the ageing criteria used in the past and the agreements on future age determination \nbased on otoliths, vertebrae and spines. Advantages and disadvantages of each calcified \nstructure for ageing and border interpretation were discussed. It was considered that bluefin \ntuna age interpretation becomes very difficult from age ten onwards using the whole vertebra \nand the spine sections methods, but this last technique continues to be useful for older ages. \nOtolith sections can be used for the whole age range. Participants agreed that none of these \nthree structures could be excluded from routine ageing because otoliths are not easily \navailable. Age estimations within the same structure and between different structures of the \nsame specimen were compared for several readers. Better precision was found between spine \nreaders compared to vertebra and otolith readers. Good age agreement was also achieved \nbetween readers of spines and vertebrae from the same bluefin for ages less than 12 years. \nPreliminary results from radiocarbon assays on otoliths were presented at the workshop and \ngave promising outcomes for bluefin tuna age validation. Also, these suggested that bluefin \ntuna can live longer than had previously been established and that a review is needed of the \ncurrently used asymptotic size and growth rate for both stocks. Another important contribution \nof the workshop was a manual for age interpretation.
Language: English
Subfield: Aquatic Science
Domain: Life Sciences
SDG: Life below water
Open Access status: green
OpenAlex ID: W2152831835