Estimates of the age structure of fish populations are central to assessing the status of fished stocks, evaluating management strategies and the impact of fishing. Determining fish age is usually done by counting growth checks in fish otoliths. This is generally a laborious, time-consuming process involving considerable preparation of the otoliths (resin-embedding, cutting and polishing) prior to ring-counting. This proposal aims to develop and validate a rapid innovative method for ageing fish based on an analysis of otoliths by NIRS. With increasing costs and, in some jurisdictions, diminishing R&D budgets, collection and ageing of representative fish samples becomes increasingly difficult. If NIRS is as efficient at determining fish age as the preliminary study suggests, it will be a breakthrough of global significance.
Commonwealth and State legislation requires that fishery resources be managed sustainably. Age-based stock assessment methods are one of the most informative tools available for assessing Australia’s fisheries. The collection of otoliths from recreational and commercial catches is undertaken across a wide range of fisheries as part of fishery monitoring and assessment programs.
This proposal addresses the need and QFRAB priority for:
• Developing innovative tools and technologies for managing Australian fisheries
• Developing more efficient, cost-effective ways of obtaining the information needed to undertake age-based fishery assessments
• More reliable fishery assessments by improving the availability and quality of age information from fish population samples
Final report
Results from the current ‘proof of concept’ study indicate that near infrared (NIR) spectra collected from fish otoliths have potential to estimate the age of Barramundi (Lates calcarifer) and Snapper (Pagrus auratus), with performance varying between species and locality of capture. A case study of hypothetical running costs suggest significant cost savings could be achieved if NIRS is used to supplement standard fish ageing methods. However, there is considerable time (i.e., at least 3 years) and start-up costs to develop and validate NIRS calibration models for fish age to a point where only model maintenance is required (i.e., running costs). Results also indicate that NIRS may be particularly useful for spatial (e.g. stock) discrimination. The potential applicability of NIRS was recognised by end-user
stakeholders in Queensland and the Northern Territory, who are proposing further research work.
Understanding what NIRS measures in fish otoliths and how this is correlated with age (or geographic location) was a common desire of fisheries end-users in all jurisdictions, because this knowledge could reduce error and would significantly enhance the applicability of NIRS technology in fisheries science.
