The Challenge

Over the past few decades, a growing body of evidence shows that the inland aquatic fauna of the WA’s southwest is in decline.

Since the turn of the century, five of the regions freshwater fish species, four freshwater crayfish species and the sole species of freshwater mussel have been listed as threatened under the Federal Government’s Environment and Biodiversity Conservation Act (EPBC Act 1999). Other species are variously listed under State legislation.

Much of this decline has been driven by the loss of suitable habitats through stream channelization, river regulation, land clearing, flood abatement and the impact of introduced species. This coupled with reductions in rainfall and subsequent run-off and aquifer recharge from the increasing impact of climate change continue to impact aquatic fauna. Adaptive management is necessary to aid their conservation.

The Solution

The marron (Cherax cainii) is a south-western Australian aquatic icon, not only for the important and unique recreational fishery that it supports, but also for its role as a biological indicator of ecosystem health.

Murdoch University scientists at a sampling site on the lower Harvey River. Photo: Murdoch University.

An aquatic survey of the lower Harvey River, conducted by Murdoch University’s Freshwater Fish Group and Fish Health Unit in 2019, found that during the hot, dry summer months, fish and crayfish were more likely found in shaded parts of the waterway with a good variety of instream habitat, including deeper pools. In nearby shallow streams, the water temperature was above the tolerance level of some species, including marron.

As climate change drives increases in temperature and decreases in rainfall, we know creating cool, shady areas and deep pools as refuges for aquatic species can help nature adapt, while simultaneously improving water quality, stabilising banks and restoring habitat.

Marron and other aquatic species will seek out cool, shady refuges during hot summer days.

Over the next three years, the Helping the Harvey project team will work on a science-led targeted restoration demonstration along the lower Harvey River, as part of the collaborative ‘Marron, More than a Meal – revive our rivers’ program.

The Marron More Than a Meal program and its supporting projects aims to demonstrate how the restoration of drainage channels can lead to an improvement of the aquatic ecosystems.

Aquatic habitat will be improved by science-led trials of instream features, while the channel banks will be fenced to exclude livestock and revegetated to provide shading and cooling of the river corridor. The site will be subject to rigorous monitoring and citizen science activities to quantify the impacts of the works and engage community around sustainable waterway management.