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Project details

Title: Developing age-length keys for the Australian SBT surface fishery based on direct age estimations using otoliths
Id: 2192
Acronym: Developing age-length keys for Aust SBT
Investigator(s): Jessica Farley
CSIRO Oceans & Atmosphere - Hobart [details]

Description: CSIRO has developed techniques to accurately estimate the age of SBT using otoliths (Gunn et al., in prep). The key object of the current proposal is to use these techniques to estimate the age of a subsample of SBT caught in the Australian surface fishery in the Great Australian Bight, and to construct an age-length key for the fishery to meet our CCSBT comitment. Although the CCSBT's immediate request is estimate the age of SBT sampled from the 2001-2 season, the ultimate goal is to estimate the age of SBT from the Australian catch annually. Since the number of otoliths collected during 2001-2 was relatively low (n=188) and very few small or large fish were sampled, the proposal also aims to include samples from the 2002-3 and 2003-4 seasons. This would allow a more robust analysis and construction of age-length keys for the fishery. We propose to determine the age of approximately 360 SBT under this project (120 from each of three seasons), and develop age-length keys for each of the three fishing seasons. Note that the CCSBT request for this type of information is ongoing, so that otoliths for the more recent season (2003-4) woul d have to be analysed in any case. At the CCSBT SC meeting in 2003, Morton and Bravington (2003) reported that between 100-200 otoliths from the furface fishery would be sufficient to provide accceptable precision (CVs under 20%). Otolith reading techniques developed by CSIRO were transfered to the Central Ageing Facility (CAF) in Victoria, as part of the CCSBTs Age Estimation Workshop (Anon, 2002), and SBT sampled from the Indonesian longline fishery are already routinely aged by the CAF under a separate AFMA funding source. We propose to that CSIRO would select and extract SBT otoliths from the CSIRO hardparts archives that were collected from the Australian surface fishery, and arrange for them to be sent to the CAF for age estimation. The analysis of the direct age data will include consideration of the approach developed
Years: 2005

There are no surveys directly linked to this project.

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