Stock enhancement of the Western School Prawn (Metapenaeus dalli) in the Swan-Canning Estuary; evaluating recruitment limitation, environment and release strategies

Project number: 2013-221

Project Status:

Completed

Budget expenditure: $200,000.00

Principal Investigator: Neil Loneragan

Organisation: Murdoch University

Project start/end date: 30 Jun 2013 - 30 Nov 2014

Contact:

FRDC

Need

The decline of the WSPs in the Swan-Canning Estuary was marked firstly in commercial catches in the 1970s and subsequently, a decline in recreational catches through to the late 1990s. Reasons for the decline are not well understood but coincide with actions to improve environmental conditions of the river system. This once abundant and iconic species is highly prized by recreational fishers in the region and is a core community value identified in surveys of river users. For this reason, addressing the population decline of the WSP is seen as priority for research under the SRT Healthy Rivers Action Plan. The WAFF project on the production and release of WSPs in the Swan-Canning Estuary, funded through WA Recreational Fishing Initiatives Fund, will work to develop production technologies for WSPs and engage the community but is not funded to fully evaluate the effectiveness of the restocking. This WAFF program needs to be supported by an investigative and evaluative program that can ascertain current population levels and factors limiting natural recruitment, optimize release strategies and evaluate cost-benefits, which forms the basis for this FRDC application.

The combination of the WAFF project with this FRDC proposal will also help evaluate the potential effectiveness of a major restocking program to rebuild the stocks of WSPs in the Swan-Canning estuary. The stock enhancement and associated community engagement program (PrawnWatch) have the potential to increase the numbers of recreational fishers in this fishery, the quality of their fishing experience and provide recreational fishers (and the broader community) with a greater understanding of the biology and ecology of WSPs and the environmental conditions of the system. The WAFF project, particularly the PrawnWatch component, also provides opportunities to engage fishers in improved stewardship of the fishery and the Swan-Canning Estuary.

Objectives

1. Evaluate the current stock status and factors affecting the natural recruitment of Western School Prawns in the Swan-Canning Estuary

2. Evaluate the costs and benefits of releasing Western School Prawns in the Swan-Canning Estuary

3. Optimise release strategies (i.e. stocking densities, size and location at release) for Western School Prawns

4. Increase stewardship of the recreational WSP fishery in the Swan-Canning Estuary

Final report

ISBN: 978-1-921877-21-6

Author: James Tweedley

Final Report • 2017-10-01 • 12.82 MB

2013-221-DLD.pdf

Summary

Keywords: Aquaculture-based enhancement, recreational fishing, restocking, post-release survival, larval ecology, larval taxonomy, fish predation

Executive Summary: This report provides the first comprehensive investigation into the biology and ecology of the Western School Prawn (Metapenaeus dalli) in the Swan-Canning Estuary in south-western Australia. It provides knowledge to help manage the fishery and evaluate release strategies for the aquaculture-based enhancement of this species. The study involved Murdoch University, the Department of Biodiversity, Conservation and Attractions (DBCA) (formerly Department of Parks and Wildlife and the Swan River Trust) and the Australian Centre for Applied Aquaculture Research (ACAAR). It was designed to complement a concurrent project to develop aquaculture techniques to produce and release M. dalli and re-engage the local community with prawning and the estuary (led by ACAAR, DBCA’s Parks and Wildlife Service and the West Australian Fish Foundation), funded by the Recreational Fishing Initiatives Fund. The Fisheries Research and Development Corporation provided matching funds for the current study. Biological data on M. dalli were collected from 20 sites in nearshore and 16 in the offshore waters of the Swan-Canning Estuary, ranging from the mouth of the system to ~40 and 30 km upstream in the Swan and Canning rivers, respectively, in every lunar month between October 2013 and March 2016. Laboratory studies were also completed to investigate the survival and growth of larval prawns in different salinity, water temperature and algal food conditions. Results were presented as part of the Prawn Watch program to engage the community in the research and encourage stewardship of the fishery and the estuary.