Project number: 2006-053
Project Status:
Completed
Budget expenditure: $425,000.00
Principal Investigator: Wayne Fulton
Organisation: Agriculture Victoria
Project start/end date: 14 Oct 2006 - 30 Jun 2009
Contact:
FRDC

Need

Murray cod is Australia’s highest profile freshwater fish species and there is a very high public expectation that fisheries for this species are managed sustainably.

There is general agreement that cod numbers have declined considerably since European settlement and whilst the exact reasons may be varied, it is clear that continued harvest is one identifiable factor that has the potential to hinder recovery. However, there is general uncertainty about a number of critical issues relating to the management of these fisheries.

A number of information gaps have been identified in relation to the recreational fisheries as follows;
- There is broad detail available on gross angler harvest but there is no detailed information on catch related to individual rivers or basins, or the level of indigenous use .
- The LML of 50cm is a critical issue as evidenced by the rapid decline in numbers of fish above this level. This also means that the survival of released fish is highly relevant.
- There is a lack of information on population structure and dynamics and, with particular reference to recreational fisheries management, there is uncertainty regarding size at maturity and whether this is constant across the basin.

Current regulations may allow the removal of fish that are sexually immature. At low fishing pressures, this may be tolerable, however, at high fishing pressure, removing spawners before they mature may threaten a stock. The management of Murray cod populations requires that the LML chosen must be robust to both fisheries management and conservation requirements, but there has been no assessment to determine the appropriate LML for sustaining these fisheries.

The information from the size at maturity as well as harvest levels and hooking survival estimates will enable the impacts of recreational fishing on cod populations to be determined via management scenario testing.

Objectives

1. Determine the rate of maturity with size and age, for Murray cod stocks in the Murray-Darling Basin.
2. Determine the levels of harvest (angler and if possible indigenous)within defined regions across the basin.
3. Determine the post release hooking survival of Murray cod under various hooking scenarios
4. Investigate sensitivity of population structure and abundance to size at maturity, legal minimum length, fishing mortality (incl. release survival) etc.
5. Evaluate management strategies in a risk-based framework for the sustainability of Murray cod fisheries across the MDB
6. The benefits of adoption by managers of the evaluated management strategies will be described

Final report

ISBN: 978‐1‐74264‐530‐8
Author: Wayne Fulton

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