Fish and crayfish

A significant amount of the value we place on our rivers, streams and estuaries centres on their iconic fish and crayfish.
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Some species are well-known by recreational fishers such as black bream, marron and prawns. There are other species that are smaller, less well-known, rare or threatened that contribute to aquatic food webs and biodiversity.  

Our Healthy Rivers program provides information on many of the species of fish and crayfish found in waterways of south-west Western Australia, including their distributions, habitats and life cycles.

Read more about fish and crayfish below.

Introduced species

There are also many species that have been introduced to our waterways. These species are predators and competitors that are harmful to our native aquatic fauna.

Sightings of aquatic pests and diseases and fish kills can be reported on the Department of Primary Industries and Regional Development’s Fish Watch website.

Indicators of waterway health

Fish and crayfish are good indicators for assessing waterway health.

They are often top predators and keystone species within the food web, which means that they are closely linked with the overall health of the ecosystem. They are affected by factors including water quality, sediment qualityaquatic and riparian vegetationaquatic habitat, barriers to connectivity, altered flow regime, past and current waterway and catchment disturbance, and overall system stability.

Monitoring fish and crayfish

Monitoring can detect changes in species composition and diversity, abundance and condition can provide valuable information relating to an aquatic ecosystem’s health.

Monitoring fish and crayfish can provide information which is not captured by monitoring other factors. For example, loss of a species which is sensitive to low dissolved oxygen may highlight an underlying problem not detected by one-off ‘snapshot’ water quality sampling. Low oxygen conditions due to algal blooms occur only in the early morning, because algae produce oxygen during the day but consume it during the night.

Similarly, a change in age demographic of fish species may highlight an issue with their ability to reproduce. For example, a weir or dam may be acting as a barrier to connectivity, impeding migration of adult fish upstream to spawning grounds.

Changes in fish and crayfish species can also highlight problems stemming from a combination of stressors. That is, where small changes in several factors can lead to a large effect on the health of a waterway. Different species have different sensitivities to the range of stressors that are known to occur in Western Australian systems, including eutrophication (nutrient enrichment)salinityerosion and sedimentationalgal blooms, removal of habitat and altered flow regimes. Monitoring individual species can help determine what stressors are impacting the system.

Healthy Rivers program

Our Healthy Rivers program collects data on south west rivers, including their fish and crayfish fauna.

This helps us to monitor river health, including negative aspects such as fish kill events as well as other threats to our waterways and guides waterway management and restoration.

More information

The following webpages provide more information and guidance: