Collie River East Branch - Duderling Pool

River condition at the Duderling Pool site on the Collie River (site code: CR491COLL1, site reference: 6124032) has been assessed on several occasions as part of the Healthy Rivers program. The most recent survey was undertaken in March 2022.

Healthy Rivers assessments are conducted using standard methods from the South West Index of River Condition (SWIRC), which incorporates field and desktop data from the site and the broader catchment. Field data collected included the following indicators, assessed over about a 100 m length of stream:

• Aquatic biota: fish and crayfish community information (abundance of native and exotic species across size classes, general reproductive and physical condition)
• Water quality: dissolved oxygen, temperature, specific conductivity, and pH (logged in situ over 24 hours), as well as laboratory samples for colour, alkalinity, turbidity, and nutrients
• Aquatic habitat: e.g. water depth, substrate type, presence of woody debris and detritus, type and cover of macrophytes and draping vegetation
• Physical form: channel morphology, bank slope and shape, bioconnectivity (barriers to migration of aquatic species), erosion and sedimentation
• Fringing zone: width and length of vegetation cover within the river corridor and lands immediately adjacent, structural intactness of riparian and streamside vegetation
• Hydrology: measures of flow (velocity) at representative locations (compared against data from stream gauging stations within the system)
• Local land use: descriptions of local land use types and activities (compared against land use mapping information for the catchment)

All the Healthy Rivers assessments are listed below:

• 2022 summer (March 2–3): Healthy Rivers
• 2018 summer (February 21–22): Healthy Rivers

At this site water quality has also been logged over an extended period on several occasions:

• 2019–20 summer (December to April)
• 2018–19 summer (November to May)
• 2017–18 summer (December to May)

Other departmental data: The Buckingham Mill Gauging Station (site reference: 612038) is about 200 m downstream of the Duderling Pool site. This gauging station is owned by the Department of Water and Environmental Regulation (the department) and has been in operation from 1999.

Search the site code or site reference in the department’s Water Information Reporting (WIR) system to find data for this site and nearby sampling points (flows, surface water quality, groundwater monitoring, department’s meteorological data). See also the Bureau of Meteorology website for additional meteorological data for the area.

This site had poor habitat complexity (i.e. minimal woody debris and bank vegetation draped in water), however, it did have an abundance of the native charophyte, nitella, observed during both 2018 and 2022 summer sampling. This plant creates important aquatic habitat for fish and invertebrates and is excellent for trapping nutrients and purifying the water.

Native charaphyte species, nitella, in Duderling Pool.

The species captured during each of the sampling events are provided in Table 1. The table includes a list of all species previously reported in the subcatchment, which indicates species that may occur at the assessment site. This list is only indicative as differences in habitat within a subcatchment naturally influence species distributions, and variability in methods between sampling programs can affect the species caught.

Eight species of fish and crayfish were captured in the March 2022 sampling. These were four endemic freshwater fish (nightfish, western minnow, western pygmy perch and freshwater cobbler), one non-native freshwater fish (eastern gambusia) and three endemic freshwater crustacean (smooth marron, gilgie, south-west glass shrimp).

The freshwater crayfish, smooth marron and gilgie, were recorded in low abundances. Fishing pressure could be a factor, particularly for marron, as the pool is a popular recreational spot; however, it is unlikely that this alone would result in the low abundances across the two sampling events. Secondary salinisation and secondary effects from eutrophication (i.e. low dissolved oxygen) are well-known issues in the catchment, and whilst marron are relatively tolerant to these conditions, it is possible that levels have reached the limit of tolerance. Low numbers could also be a function of poor habitat complexity, with large woody debris appearing to have been removed from much of the area. More work is needed on establishing current distribution and potential association with these water and habitat quality conditions.

The absence of koonac from assessments is likely related to a preference for other habitats in the subcatchment that dry seasonally. In the dry season the koonac create burrows to maintain contact with the water table and are rarely coinhabiting areas with marron, which require permanent water.

The photos of fauna provided are linked to more information about each species, including maps of where each species is expected across the South West.

Note: collection of fauna from inland aquatic ecosystems across Western Australia requires a licence from the Department of Primary Industries and Regional Development (DPIRD) and the Department of Biodiversity, Conservation and Attractions (DBCA). All species collected must be reported to these agencies as part of licence conditions.

Only fish and freshwater crustaceans (crayfish and shrimp) that typically inhabit river channels are targeted by the standards SWIRC sampling methods; however, other species are periodically captured in traps and/or observed (e.g. turtles, rakali native water rats, tadpoles). The following non-target species were identified at this site:

• The south-western snake-necked turtle (Chelodina oblonga) was recorded during assessments in 2018 and 2022.

For more information on this and other aquatic species please see the River Science fauna page.