Recent assessments of the NPF have identified a need for the fishery to be managed at a finer spatial scale than that of the NPF managed area (AFMA 2003, DEH 2003). The stocks of some prawn species appear to comprise regional subpopulations that, although not genetically isolated, mix little enough to be manageable as separate stocks. This view is consistent with the experience that depleted stocks in some regions (e.g. north of Mornington Island and Weipa) have not recovered when stocks elsewhere in the NPF were healthy.
The assessments also identify a need to broaden the scope of management of the NPF beyond prawn stocks, iconic species and bycatch to include benthic habitats and species. Prawn fishing has a number of impacts on the ecosystem, including: removal of target species; removal of bycatch and byproduct; removal of benthic plants and animals; removal of habitat-forming species; disruption of sediment structure; suspension of sediment; and feeding of dolphins, sharks, seabirds, fish and benthic invertebrates with discards (Poiner et al. 1998). Some impacts, such as removal of seagrass in nursery habitats, are known to negatively affect prawn stocks. Other impacts are likely to affect stocks in unknown ways, positively or negatively, and in some habitats may affect the sustainability of the stocks.
Broadening management of the NPF to include impacts on benthic ecosystems is therefore prudent from both an environmental and industry viewpoint. It is also consistent with the recommendations of the NPF strategic assessment (DEH 2003), and will prepare the industry for the increasingly sophisticated environmental awareness of export markets.
Management of the NPF is currently based on sound stock assessment and population monitoring procedures, and uses maximum sustainable yield as the management limit reference point. Spatial stock assessment has been investigated with mixed success, but is not used operationally. Current environmental management focuses on fragile habitats (mainly seagrass), prawn spawning areas, iconic species (e.g. turtles) and bycatch. Recently, ABARE suggested a move towards economic efficiency targets, such as maximum economic yield. (Rose and Kompass 2004).
To do this the FRDC project 2004/022 will integrate the existing stock and economic assessments into an MSE process.
To enable stock, economic and environmental objectives to be effectively pursued in a spatial context and with minimal conflict, the stock, economic, bycatch and ecosystem components of NPF management must be integrated into a single, spatially explicit management framework. This project will contribute with major missing elements for that integration and will develop this needed spatial management framework. Equally, the timing of this proposal is opportune given that stock assessment and monitoring are already mature, interactions with iconic species and bycatch are becoming well understood, and the integration of stock assessment with economics is currently underway. To achieve highly effective technical communication and integration we will involve PIs from past and present projects and a Steering Committee with members from CSIRO AFMA staff and NORMAC-REC and NPF-RAG members.