Canning River - McNess Drive

River condition at the McNess Drive site on the Canning River (site code: CR45CANN1, site reference: 6167146 – previously reported as site code: CONF1, site reference: 6165345) has been assessed on several occasions since 2009. This includes 18 individual fish and crayfish surveys as part of the Healthy Rivers program, including previous versions of the program. Most recently it was assessed three times over the dry season of 2021–22 (during December 2021 and February and May 2022). Additionally, water quality was logged at 30-minute intervals between November 2021 and May 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 from the broader catchment. Field data collected include 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)

Previous assessments at this site are listed below and include some or all of the measures above. Note: aquatic fauna sampling methods have been specified given variations between surveys.

For a subset of the assessments above, water quality loggers were deployed for extended periods (see below). This enabled assessment of water quality responses to changes in climate, streamflow and factors such as the intactness of vegetation within the river corridor. Among other things, this allows detection of sub-optimal water quality conditions which can be missed during the standard 24-hour assessment.

• 2015–2016 (Nov–May): Healthy Rivers
• 2018–2019 (Nov–Apr): Healthy Rivers
• 2021–2022 (Nov–May): Healthy Rivers

Other departmental data: The McNess Drive site is about 14 km upstream of the Department of Water and Environmental Regulation's (the department) flow gauging station known as Seaforth (site reference: 616027), which has been in operation since 1997.

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, the department's meteorological data). See also the Bureau of Meteorology website for additional meteorological data for the area.

Scheme water is released from six points along the Canning River over the dry season (about November to May) to maintain key ecological function, provide water for licensed use, and contribute to maintaining the cultural and social values of the river.

These Environmental Water Provisions were formalised in the Middle Canning River surface water allocation plan (2012) and are set out in the Water Resource Management Operating Strategy associated with Water Corporation’s licence for the Integrated Water Supply Scheme. The allocation plan is evaluated and updated as required.

Regarding river health, the release regime was designed to support pool ecology through maintenance of water quality and habitat availability, including providing for localised movement of aquatic fauna. This follows guidance from the Ecological Water Requirements for the Lower Canning River (2010) and has been adapted over time following recommendations from ecological monitoring undertaken as part of the allocation plan evaluation.

The McNess Drive site is 6 km downstream of the Canning Dam, which is the top of the catchment in terms of river connectivity and fish passage.

Flow data are provided in the next section.

Continuous water quality data collected between November 2021 and May 2022 are displayed below. Water quality was generally optimal in terms of dissolved oxygen and water temperature.

The concentration of dissolved oxygen in the water never fell below the 4 mg/L threshold,¹ and the diurnal range was largely optimal as well (<4 mg/L range over a 24-hour period). Water temperature exceeded the 25°C threshold² for just 1.3 per cent of the monitored period. This data is consistent with previous assessments which have recorded optimal water quality at the site.

The pH data is incomplete because it did not meet quality control checks. Data collected after the first maintenance check was discarded. Specific conductivity and pH remained within acceptable ranges, based on expectations of natural ranges for freshwater rivers of south-west Western Australia.

Footnote:

¹ A lower limit of 4 mg/L is taken from the SWIRC where it is used as a guideline limit for condition scoring. This level aligns with Beatty et al. (2013) where south-west native fish species were shown to typically reside in sites with levels above 4 mg/L.

² An upper limit for temperature is nominally set at 25°C based on the range recorded in sites where south-west native fish species are typically found to occur (Beatty et al. 2013).

The species captured at the McNess Drive site during each of the sampling periods since 2009–10 are provided in Table 2. The table includes a list of all species previously reported in the subcatchment, which provides an indication of species that may occur at the assessment site. As differences in habitat within a subcatchment naturally influence species distributions, and variability in methods between sampling programs can affect the species caught, this list is only indicative.

Four species of fish and four crayfish species were recorded during the 2021–22 sampling. This included three native freshwater fish species, one exotic species of fish, three native crayfish species and one species of exotic crayfish.

Western minnow, western pygmy perch and nightfish were all abundant, with the population of pygmy perch particularly large compared with Lissiman Street, Brookton Highway and Stocker Road. Juveniles were recorded for both western minnow and western pygmy perch. Freshwater cobbler were not recorded during 2021–22; however, this absence of cobbler is not immediately concerning as they can be present in an area but not captured and are known to undertake localised migrations. Cobbler have been previously recorded in the area in 2009–10 and 2015.

Both of the commonly found crayfish species (smooth marron and gilgie) were present in 2021–22 and both species recorded juveniles. Smooth marron were dominant and were more abundant at this site than at Lissiman Street, Brookton Highway or Stocker Road, as were nightfish and western pygmy perch, indicating the site has particular ecological value.

The exotic eastern gambusia was abundant and actively recruiting (presence of juveniles). Gambusia were more abundant at this site than at Lissiman Street, Brookton Highway or Stocker Road, which presents a direct risk to the native fish species. The exotic crayfish yabby was also present, although in low numbers and with no juveniles recorded. The yabby has been recorded intermittently at this site (see table 2).

Only fish and freshwater crustaceans (crayfish and shrimp) that typically inhabit river channels are targeted by the standard SWIRC sampling methods. However, where other species were caught or observed (e.g. turtles, rakali-native water rats, tadpoles), these are mentioned below in the other aquatic fauna section.

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.

Carter’s freshwater mussel (Westralunio carteri) was observed at the McNess Drive site during the 2021–22 assessments and has been recorded during previous assessments. This mollusc is the sole endemic freshwater mussel species in Western Australia and currently listed as vulnerable on the International Union for Conservation of Nature’s (IUCN) red list of threatened species (because of declining range, which is largely attributed to the effects of salinity).

Although not targeted by collection methods, south-western snake-necked turtles (Chelodina oblonga) and unknown species of frog or tadpoles (Anura) were collected in fish nets and/or traps.

The native, semi aquatic-mammal rakali (Hydromys chrysogaster) is known to inhabit the area and footprints have been noted in previous years along with other evidence, although none were recorded during the 2021–22 assessments. This species is listed by DBCA as a Priority 4 species (rare, near threatened and other species in need of monitoring).

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