Sabina River 3
Basin : Busselton Coast
Catchment : Vasse - Ludlow rivers
River condition at the Sabina River – Sabina River 3 site (site code: VR60SABI3, site reference: 6100032) on the Sabina River has been assessed as part of the Healthy Rivers program using standard methods from the South West Index of River Condition (SWIRC). The SWIRC 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)
This is the first known ecological assessment of this site.
Other data:
There are currently no monitored gauging stations on the Sabina River. However, the Sabina Diversion – Wonnerup East Road gauging station (site reference: 610025) is about 7 km upstream of the assessment site on Sabina River main drain. This gauging station is owned by the Department of Water and Environmental Regulation (the department) and has been in operation since July 2000.)
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.
Condition summary
The Sabina River is an intermittent river (only flowing in the winter months). The lower catchment has been significantly altered, with about 60 per cent of flow from the upper catchment diverted into the Sabina Diversion Drain to prevent flooding of the Busselton township.
It should be noted that considerable effort is underway to improve health in the system and wider catchment under the Revitalising Geographe Waterways program, run by the multi-agency Vasse Taskforce.
The assessment was carried out within the Noongar season of Bunuru (March). Bunuru is generally the driest and hottest part of the year with little to no rain.
The image below indicates conditions at the time of sampling in March 2022. Further images are provided in the gallery at the bottom of the page to show general site conditions.
SABINA RIVER, MARCH 2022
A summary of aquatic biota detected over the different sampling events is provided in the section below. For other site data please contact the department’s River Science team (please provide the site code and sampling dates).
Species found in subcatchment
Species found at the site
Fish and crayfish
The species captured at the Sabina River – Tuart Drive site during each of the sampling periods 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. Below are some of the notable findings from the assessments.
Four species of fish were found at this site in the March 2022 assessment. These were one native freshwater fish (nightfish), one native freshwater-estuarine species (blue-spot goby), one native crustacean (south-west glass shrimp) and one non-native freshwater fish (eastern gambusia).
Eastern gambusia (mostly adults) were the most abundant freshwater fish detected. Eastern gambusia tend to thrive in disturbed or degraded systems, being tolerant of poor water quality, such as low dissolved oxygen concentrations, and not impacted by significant habitat change. They are therefore often able to outcompete more sensitive native species.
It was encouraging to find nightfish (albeit in low abundance) and south-west glass shrimp, which were absent from the Sabina River 1 assessment site upstream. This suggests that these species are using this pool as a refuge area during the dry season. It should be noted that dissolved oxygen was below the recommended guideline value of 4 mg/L used for freshwater fish species of Western Australia’s South West (Beatty et al. 2013). Low oxygen concentrations (below 4 mg/L) are not uncommon through the latter part of the dry season in many South West rivers and native fish are able to tolerate these conditions for short periods of time. However, their ability to withstand these situations and compete with invasive species like the eastern gambusia is reliant on their physical condition, and this is a function of ecosystem health (e.g. availability of food, habitat, and otherwise good water quality).
A small number of blue-spot goby was found during the March 2022 assessment. This species is known to inhabit both estuarine and freshwater parts of rivers and estuaries and can move between these habitats or complete their life cycle completely in either area.
Western pygmy perch and western minnow have been found in the subcatchment (including the Sabina River 1 upstream assessment site) and would be natural expected at this site based on habitat preferences. The reason for their absence is not known but is most likely attributed to poor water quality, particularly low dissolved oxygen concentrations (as discussed above). Algal scum was also present on the surface of the water, which could be a driver of the low oxygen conditions.
Salinity was 1319 mg/L, which is within the marginal-brackish salinity category. This is a higher level than seen in most of the freshwater systems that these species appear to prefer; however, many of the local species are known to occur in waters between 500 to 2500 mg/L (Mayer et al 2005).
Further investigations are required to better understand species distribution and needs within the Sabina River during the dry season. A key part of this is locating primary dry-season refuge pools (providing better water quality and habitat).
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.
Other aquatic fauna
Although not directly targeted as part of the Healthy Rivers assessment, the following species were recorded:
- a south-western snake-necked turtle (Chelodina oblonga)
- diving beetles (Family Dytiscidae)
- water boatman (Family Corixidae).
