Donnelly River - Chappel Bridge

River condition at the Chappel Bridge site on the Donnelly River (site code: DR182DONN1, site reference: 6081062) has been assessed on several occasions as part of the Healthy Rivers program.  The most recent survey was undertaken between 27–28 February 2023.

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)

All of the Healthy Rivers assessments at this site are listed below, as well as any known third-party assessments. Note: aquatic fauna sampling methods have been specified, given variations between surveys at this site.

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.

• 2016–2017 (Oct–May): Healthy Rivers (Department of Water and Environmental Regulation)
• 2017–2018 (Nov–Mar): Healthy Rivers (Murdoch University - Beatty et al. 2018)
• 2019-2020 (Dec-Apr): Healthy Rivers (Department of Water and Environmental Regulation)
• 2020–2021 (Aug–May): Healthy Rivers (Department of Water and Environmental Regulation)
• 2022–2023 (Dec–May): Healthy Rivers (Department of Water and Environmental Regulation)

Other departmental data: The Chappel Bridge site is 50 m downstream of the Department of Water and Environmental Regulation's (the department) flow gauging station known as Chappells Bridge (note different spelling); site reference: 608028, which has been in operation since 2016. The site is about 30 km upstream of the department's Strickland gauging station (site reference: 608151), which has been in operation since the 1940s.

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.

The species captured during each of the sampling events at the Chappel Bridge site are provided in the table below. 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.

The most recent sampling event was during February 2023. Nine species of fish and crayfish were captured. This includes three endemic freshwater fish (nightfish, western minnow and western pygmy perch) and three endemic freshwater crustaceans (south-west glass shrimp, smooth marron and gilgie). February 2023 was the first time the gilgie has been recorded at this site.

Several native and exotic species are known to occur at the site, these are discussed below:

• Nightfish– endemic freshwater fish. Present during all sampling events except August 2020.
• Blue-spot goby– native fish known to inhabit both estuarine and freshwater parts of rivers and estuaries. The species was absent from all three sampling events in 2020 (January, February, and August). This species is known to move within riverine environments; their absence may have been because of natural changes in distribution, as they were detected again during the February 2023 assessment.
• Pouched lamprey– an anadromous fish that migrates between freshwater rivers to marine environments to complete their life cycle.  The absence of lamprey from most SWIRC assessments is not a significant concern as this species typically migrates in a brief period around peak winter flow (which is largely outside of the usual assessment periods) and only in high flow years. Outside of the short migration periods lamprey are unlikely to enter traps.  In the early stage of their life cycle, juvenile lamprey (ammocetes) burrow in sand in upper reaches of river systems.  They migrate to the ocean where they may remain and feed for about two years. Eventually lamprey will migrate back to river systems to spawn and die. The species is priority 3 species (poorly known) under the Biodiversity Conservation Act 2016 (Western Australia).
• South-west glass shrimp– freshwater crustacean. This species has been detected during most assessments, and again during 2023. The species is resident and expected to be detected if present. Occasional absences may reflect sampling effort and variations in natural distribution within the site.
• Koonac – freshwater crayfish. The catchability of this species is highly dependent on the timing of sampling and specifically location within a system. Koonac are generally found in the parts of rivers that dry seasonally, retreating to burrows for large parts of the year.  The Chappel Bridge site has areas of both permanent water and seasonal inundation, and koonac are most likely to be detected during periods of inundation in the habitats that dry (smooth marron being supported by the permanent habitats). As such, the absence of koonac since 2018 is not a significant concern but should be monitored over future sampling events.
• Rainbow trout, redfin perch and eastern gambusia – exotic freshwater fish species. These species have previously been recorded at the site but were not recorded in August 2020. Redfin perch and gambusia were both detected again during the latest assessment in February 2023

During the first wet season sampling (August 2020) there was a lower richness of species recorded. During February 2023 the numbers of species detected increased. The lack of detection of some species during 2020 (but particularly during August 2020) is expected to be related to low sampling effort, i.e. species are present but were not detected or species had migrated away from the site temporarily.

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 standard 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:

• Carter’s freshwater mussel (Westralunio carteri) was recorded in 2016, 2017, 2018, and 2020. This species 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).
• Rakali (Hydromys chrysogaster), native, semi-aquatic mammal, was recorded during the latest assessment, including footprints and discarded prey items (crayfish and freshwater mussels). 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 recorded aquatic fauna and other aquatic species, please see the River Science fauna page.