Freshwater fish habitat
Australian native fish need a range of habitats to complete their life cycle. Widespread, good quality fish habitats increase the distribution and abundance of native fish.
Native fish move between habitats for the following reasons:
- food availability
- seasonal access
- breeding sites
- nursery areas.
Most native fish species use specific seasonal and life stage habitats. For example, Pacific blue-eyes prefer to inhabit small, shallow, slow-flowing coastal streams; saratoga prefer billabongs with floating aquatic vegetation and cod prefer large snags in deep water.
Freshwater fish habitats include:
- habitat zones (rivers, lakes, wetlands, creeks, swamps etc.) in the upper, middle and lower sections of a waterway
- microhabitats within each of these zones including banks, snags, rocks, channels, substrates, riffles, macrophytes (aquatic plants) and riparian vegetation.
Habitat zones influence the makeup of fish communities. This is particularly so in the headwaters of a catchment, where fish communities tend to be made up of fish species that specialise in living in the upper section of the waterway. Microhabitats have more influence on the distributions of individual fish species.
Quality fish habitats
Quality fish habitats provide the following benefits:
- support fisheries resources
- increase biodiversity
- improve water quality
- supply food for a variety of aquatic animals
- increase the population and abundance of native fish
- reduce the impacts of pest fish (e.g. carp, tilapia and gambusia).
Good quality, diverse fish habitats limit the impacts of invasive aquatic pests and weeds by giving native species a competitive advantage. Fish habitats help our native fish adapt to changing environmental conditions (including withstanding the effects of extreme events like fire, drought and floods).
The importance of riparian vegetation
Riparian vegetation is an important part of fish habitat. It provides:
- erosion protection
- improved water quality
- buffering to the surrounding land use
- shade, cover and water temperature regulation
- up to 90% of food sources (detritus and insects)
- habitat in the form of snags (logs, roots, branches and leaves).
Healthy riparian vegetation equals a healthy fish habitat.
Threats to freshwater fish habitats
Australian native fish populations have reduced in distribution and abundance as a result of human-induced habitat modification and loss, including:
- waterway modification, flow regulation and waterway barriers
- development of surrounding land and loss of riparian vegetation
- introduction of exotic species and weeds
- removal of instream habitat (snags, sediments and aquatic vegetation).
Fish habitat as defined under the Fisheries Act 1994 includes land, waters and plants associated with the life cycle of fish, and includes land and waters not presently occupied by fisheries resources. The Act provides for the management, protection and enhancement of fish habitat.
Fish habitat can be protected via the declaration of a fish habitat area or through the protection of specific habitat types (e.g. snags or wetlands).
Improving freshwater fish habitats
To reduce the impacts of the threats and to improve the freshwater fish habitats we need to:
- maintain and protect aquatic and riparian vegetation
- increase buffer zones
- maintain and re-introduce snags
- protect and restore the natural water flow regimes and connectivity of waterways
- remove weeds and pest species
- revegetate the riparian zone.