Water quality monitoring in the Swan River. Photo by K Trayler/DBCA
Water quality monitoring in the Swan River. Photo by K Trayler/DBCA

DBCA's Biodiversity and Conservation Science division has a key role in monitoring, evaluating and reporting on the environmental health of the Swan Canning Estuary and its catchment.

Environmental monitoring is focused on water quality and biological indicators including fish and seagrass.

What we do

  • develop an understanding of waterway function
  • track trends
  • measure compliance against management targets
  • monitor the extent and severity of low oxygen and algal blooms
  • report changing conditions to the community
  • inform catchment models
  • guide management decisions and incident response
  • determine the effectiveness of estuary and catchment management measures

Microalgae activity

The weekly Microalgae Activity Report (MAR) provides information on microalgae activity levels, the probability of discoloration and/or scum formation, and potential warnings. This is based on data collected at 20 routine monitoring sites throughout the Swan Canning river system. Concentrations of chlorophyll-a, a plant pigment, are used to estimate microalgal activity.

This week's Microalgae Activity Report

Week starting: Monday 20th March 2023 (next update scheduled for 30th March 2023)

Microalgae activity was high at Woodbidge in the Swan, and between Shelley and Langford in the Canning this week. 

The bloom of the paralytic shellfish toxin-producing alga Alexandrium that was previously evident in the Swan River between Matilda Bay and East Perth now predominantly located between East Perth and Maylands. As an on-going precaution: 

  • People are reminded of permanent Department of Health advice not to eat shellfish (mussels, other bivalves and gastropods) caught in the river system. Commercial shellfish are not impacted.
  • Eating affected crabs and mussels may be dangerous, and in extreme cases, fatal. To ensure your blue swimmers are Alexandrium-free, remove the head, guts (mustard) and gills before freezing, cooking or eating them. Cooking whole crabs does not destroy the toxins and could potentially spread the toxin from crab guts into the flesh or broth. Freezing whole crabs could result in PSTs spreading to the flesh during thawing.
  • And remember - you still have to land and transport blue swimmers home as whole crabs, unless you plan to eat them immediately.
  • You can report pollution and other events in the Swan Canning Riverpark, such as injured animals, algal blooms and other environmental concerns, to DBCA's Riverpark Duty Officer on 9278-0981.


Fish responsibly - dolphins, particularly calves, can get tangled in fishing line. Please collect and responsibly dispose of unwanted fishing line.


MAR alert levels


  Low Medium High Alert
  Low levels of microalgae with no likely visible impact Possibility of discolouration and/or scum formation High probability of discolouration and/or scum formation Presence of species potentially harmful to aquatic life, OR human health requiring public advice
Chlorophyll-a (µg/L) < 4 4 - 10 > 10 N/A

Routine water quality monitoring

Water quality monitoring occurs on a weekly basis in the Swan Canning Estuary and fortnightly in its catchment.

Parameters collected include salinity, temperature, dissolved oxygen, nutrients and phytoplankton.

Water quality reports (or profiles) are prepared weekly to share information on waterway conditions. The most recent reports are available for download at the bottom of this page. Weekly reports produced in 2022 are also available to download. 

Weekly water quality reports produced before 2022 are available by emailing DBCA: riversandestuariesscience@dbca.wa.gov.au.

Current algal bloom warning information is also available.

More water quality reports are available on the Parks and Wildlife Service website:

Monitoring and evaluating fish communities

In collaboration with Murdoch University, DBCA reports annually on fish communities as an indicator of the condition of the Swan Canning Estuary. Since 2012, fish communities have been monitored in summer and autumn at six nearshore and six offshore sites in the upper, middle and lower Swan, as well as in the lower Canning.

The latest (2022 and 2021) reports are available for download at the bottom of this page. Historic reports are available on the Parks and Wildlife Service website. Sampling for the next report will begin in early 2023.

Seagrass health and distribution

Seagrasses are some of the most productive organisms in the world. Productivity rates can be twice that of forests. There are three main species of seagrass in the Swan Canning Riverpark, with paddleweed (Halophila ovalis) the dominant species. They play a role in maintaining oxygen levels at the sediment/water interface, support diverse and productive faunal assemblages and are an important food source for animals such as WA’s iconic black swan. Since 2011, seagrass has been monitored annually between November and March at six locations. Historic reports are available on the Parks and Wildlife Service website. A five-year report on seagrass condition is being compiled.


DBCA investigates the type, distribution, and concentration of non-nutrient contamination in the Swan Canning Estuary. Non-nutrient contaminants include metals, per- and poly-fluoroalkyl substances (PFAS), pesticides, petroleum hydrocarbons and polychlorinated biphenyls. These are typically the result of historic and current agricultural, urban and industrial activities. They can enter the Swan Canning Estuary system through drains, tributaries, groundwater, in-river activities such as recreational boating and the disturbance of acid sulphate soils. The most recently released reports on contaminants are available for download at the bottom of this page. Historic reports are available on the Parks and Wildlife Service website.


Page reviewed 23 Mar 2023