Our ability to assess the status of many important fish species is restricted by the inability to accurately estimate their biomass. In addition, the high costs of such surveys mean that they are not conducted for many species within Australia's Fisheries. Ichthyoplankton surveys to determine egg production and biomass (such as through the daily egg production method (DEPM)) offer an effective means to get this information. However, current techniques cannot be applied broadly because many fish have morphologically identical eggs and molecular sequencing is prohibitively expensive and time consuming. These issues were highlighted in the DEPM assessments for blue mackerel and red bait (FRDC 2002/061 & 2004/39) where there was poor success in morphological identification of fish eggs collected in plankton tows. These projects identified the need to develop an accurate, rapid and inexpensive technique for fish eggs identification. This project will assess the suitability of developing this technique with the ultimate aim of conducting icthyoplankton surveys to inform a DEPM for mackerel species (Qld, NT and WA), pilchard and herring species in the developing tropical small pelagics fishery(NT) and black jewfish (NT, WA, Qld). While the development is focused on tropical species the technique will have application in many southern fisheries.
This project was developed under the steerage of the Northern Research Partnership (NRP) and addresses northern Australia priorities around developing better biomass estimation methods for Spanish/grey mackerel and for the new multi-species small pelagic and Coastal Line Fisheries in the NT.

Queensland and the Northern Territory legislations require sustainable harvest of fish resources and their optimal use. Reliable and robust information on the status of fished resources are central to achieving such outcomes. Each jurisdiction has its own management regime for the mackerel fisheries in their corresponding waters. The lack of information on stock structure, however, means that the appropriate scale of management is not known. As well, fishers have no guidelines to encourage investment and long-term involvement in a fishery that supplies lucrative overseas markets. These management- and fisher-unfriendly circumstances must be viewed in the context of dramatic declines in catches of grey mackerel along the Queensland east coast, combined with significant and increasing catches in other parts of the species' northern Australian range. Such a scenario highlights the urgent need for information on the stock structure of this species.

At its August 2003 meeting, the Northern Australian Fisheries Management Forum (NAFMF) signaled its intention to move from single jurisdiction-based fishery management towards a more integrated approach that reflected the management needs of species across their northern Australian range. In 2004, NAFMF progressed this undertaking for grey mackerel, with the development of an operational plan for sustainable harvest across northern Australia. In order to obtain the maximum benefit from this initiative, the underlying stock structure of grey mackerel must be established. Furthermore, the proposed project is consistent with the strategic directions of the Northern Territory Strategic Plan for Fisheries Research and Development, particularly those directives related to the sustainable harvesting of fish and other aquatic resources, and the optimum utilisation of fish and aquatic resources.