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Title:

The impact of habitat loss and rehabilitation on recruitment to the NSW eastern king prawn fishery

Project Number:

2013-006

Organisation:

NSW Department Of Primary Industries Orange

Principal Investigator:

Matt D. Taylor

Project Status:

Current

FRDC Expenditure:

$421,928.39

Program(s):

Environment

Need

This project addresses the 2013 NSW FRAB research priority “Understanding environmental impacts on commercially important species”. The paucity of knowledge of EKP nursery habitats in NSW is a significant problem, as the estuarine nursery phase is the period where EKP are most likely to be affected by (non-fishing) anthropogenic activities and potentially represents a recruitment bottleneck which directly affects productivity. Investment in research in the southern United States has found that: 1) There is quantitative relationship between intertidal vegetation and the yield of penaeid prawns (Turner, 1977); 2) Restoration of connectivity and rehabilitation of saltmarsh areas has a quantifiable benefit for prawn fisheries (Rozas et al., 2005). Research into estuarine nursery habitats for EKP in south-eastern Queensland forms the basis of the sustainable management of their prawn fishery through a recruitment index. In NSW, however, there is a paucity of knowledge on the early life history stages, including recruitment to estuaries, use of estuarine habitats by natural recruits, and factors that affect growth and survival of young EKP. Regulating river flows in estuaries and restricting tidal flow into wetlands can destroy connectivity between new recruits and their nursery areas. NSW commercial fishers have indicated that wetlands in the lower portion of estuaries (such as Hexham Swamp in the Hunter River) were historically significant nursery areas for EKP, prior to their destruction. These anecdotes highlight a need to understand the nursery habitats and hydrographic conditions that contribute to the EKP fishery in NSW. An understanding of the nursery function of these areas, the extent of habitats lost, remaining and restored, is required to provide a basis for assessing the competing costs and benefits of habitat rehabilitation. Further, this project represents an important case study to highlight the potential financial benefits to fisheries of rehabilitation and restoration of appropriate estuarine habitats.

Objectives

1. Determine to what extent young eastern king prawns (EKP) are using natural, degraded or rehabilitated habitat in estuaries, and the contribution of these habitats to the fishery

2. Determine the hydrographic conditions which provide for maximum growth and survival of EKP within nursery habitats

3. Determine the extent of key EKP habitat lost and remaining in a number of key estuaries between the Tweed and the Hawkesbury

4. Outline the potential improvements to the EKP fishery that could be achieved through targeted wetland rehabilitation and freshwater flow management

5. Extend information on EKP habitat requirements to commercial fishers, landowners and other catchment stakeholders and incorporate recommendations into fisheries or water management