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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

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

Habitat – Fishery Linkages and Implications for Habitat Repair

Final Report
ISBN:978-1-76058-320-0
ISSN:
Author(s):Dr Matt Taylor
Date Published:June 2019
New South Wales Department of Primary Industries (NSW DPI) presents new information exploring the linkages between estuarine habitats and exploited species. Establishing linkages between fisheries and the habitats that support them is essential to the effective management and repair of marine and estuarine seascapes. A combination of novel chemical techniques, extensive field work, and numerical modelling was undertaken in several of New South Wales’ most important estuarine fisheries between 2013-2016. This allowed the description of habitat-fishery linkages for penaeid prawn species, and other exploited fish and crab species. The findings demonstrate the extensive value of estuarine habitats that is realised through fisheries harvest, and this will support the business case for repair of these habitats in the years to come.
Using Eastern King Prawn as a focal species, this project quantitatively defines habitat-fishery linkages, and shows how the nursery concept can support the prioritisation, planning, design and assessment of estuarine habitat repair projects in New South Wales. We also attribute potential economic value that can be derived from estuarine habitats from a broader fisheries perspective, and consider the potential benefits that may be realised from targeted repair.
 
 
Objectives:
1) Determine to what extent young Eastern King Prawn 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 Eastern King Prawn within nursery habitats;3) Assess the extent of key Eastern King Prawn habitat lost and remaining in the Hunter and Clarence river estuaries;
4) Outline the potential improvements to the Eastern King Prawn fishery that could be achieved through targeted wetland rehabilitation;
5) Extend information on habitat-fishery linkages to commercial fisheries, landowners and other catchment stakeholders and incorporate recommendations into fisheries or water management;
While Eastern King Prawn were the focal species for this project, feedback from FRDC requested that where possible the project broaden its scope to account for other exploited species. Consequently, a further objective was addressed through the project:
6) Establish quantitative habitat-fishery linkages for the main exploited species in both the Hunter River and Clarence River systems.