Assessing Waterway Health by Investigating Fish Communities

Murdoch University researchers Kurt Krispyn (left) and Brian Poh (right) undertaking fish community index sampling in the Murray and Serpentine Rivers

Through PHCC’s Healthy Waterways Program, we continue to use best practise management to improve the health, biodiversity and ecosystem function of our rivers and estuary. This not only encompasses the implementation of on-ground activities, it too recognises the importance of gathering valuable data through the appropriate scientific processes to inform future decision making.

The Fish Community Index monitoring tool, developed by Murdoch University’s Chris Hallett et al., was identified as a means to determine the current condition of estuarine components of our rivers and the estuary. It is argued that fish communities provide vital ‘signals’ about the ecosystem health of estuaries. Therefore, it is the development of this index that exposes the impacts and traits of estuarine environments on aquatic fauna such as fish, thus indicating to us the current condition of the water body.

Using a specific methodology, this monitoring samples fish communities across a number of identified sites. Seine netting is conducted in shallow waters (< 1m) and gill netting is conducted in deeper waters (>1m) where all species are identified, recorded then released. This data is then used to calculate fish community index scores against a benchmark or reference conditions, which in turn, is then constructed into a simple report card with grades; A ‘very good’, to E, ‘very poor’. This information is critical in determining and prioritising future actions across our waterways and complements research findings already completed such as, river health assessments that have been performed on all three rivers and the work achieved through the ARC Linkage project, see here for more information.

For the Peel and through PHCC’s Healthy Waterways Program, in partnership with Murdoch University a total of 48 nearshore sites and 21 offshore sites have been identified across five regions (lower & upper Murray River; Serpentine River; western & eastern Peel Estuary; northern & southern Harvey Inlet; Mandurah channel) to undertake fish community index sampling in Summer and Autumn 2021. To date, summer sampling has been completed where a total of 636 fish were caught and released. There were a number of bony fish (teleosts) and rays such as the Southern Eagle Ray (Myliobatis tenuicaudatus) and Smooth Stingray (Bathytoshia brevicaudata) that were seen throughout the samples. The most numerous fish recorded were the Perth Herring (Nematalosa vlaminghi) and Sea Mullet (Mugil cephalus) which in fact, represented 38% and 13% of all fish recorded, respectively. Furthermore, among each of the five regions, between 7 and 11 species were recorded in the Peel and Harvey regions, and Serpentine River compared to lower numbers of species (2 and 5) being found in the Lower and Upper Murray River. However, in this sampling event, it was these two regions that had highest number of fish (127 and 239, respectively) compared to 25 – 65 in the other regions. The health scores for each region in this summer sampling event will be calculated once all of the samples have been collected and processed by Murdoch University.

We are looking forward to seeing the results from the Autumn sampling and are excited to share the final report card with our community, stakeholders and project partners.

This project is supported by PHCC through funding from the State Government’s Royalties for Regions, the Alcoa Foundations Three Rivers, One Estuary Initiative and the Australian Government’s National Landcare Program.