Developing a fishery independent estimate of biomass for snapper
South Australian Research and Development Institute
Mike A. Steer
This study was undertaken by the South Australia Research and Development Institute (SARDI). Through overcoming considerable technical challenges, this study was the first to successfully develop a relatively non-destructive molecular probe that can reliably identify Snapper (Chrysophrys auratus) eggs and larvae in mixed ichthyoplankton samples. This highly-specific molecular probe targets Snapper ribosomal (r)RNA and when conjugated with a reactive molecule produces a highly visible blue colour in positive reactions. Snapper eggs are subsequently easily detected using a standard stereo dissecting microscope. This novel use of an established molecular technique has re-invigorated the capability of using the daily egg production method (DEPM) to provide a fishery-independent estimate of spawning biomass for Snapper and has also increased its applicability to other species where egg identification has been problematic. This research has reduced the need to exclusively rely on fishery-dependent catch and effort data to assess Snapper fisheries and has demonstrated that the incorporation of the DEPM into South Australia’s existing assessment program is relatively cost-effective and likely to benefit the management and industry. Adding the DEPM will contribute an extra unbiased source of information that can be synthesised with existing fishery-dependent data streams that will lead to more confident assessments of the stock and ensure the long term sustainability of the State’s Snapper resource.Keywords: Snapper, Chrysophrys auratus, Spawning Biomass, Daily Egg Production Method, South Australia, In-situ Hybridisation, Egg Identification, Cost-Effective Application.
1. To develop a DEPM for snapper that provides the most accurate estimate of biomass and integrates with the on-going assessment and management of the resource.