Fish are valued for supporting healthy ecosystems, and for recreational fishing.
The strategy will consider opportunities to protect and enhance native fish populations through on-ground works and other initiatives e.g.
- Planting vegetation along streams
- Providing natural stream flows
- Reducing pollution
- Installing fishways that allow fish to move past barriers (e.g. weirs, dams, pipes) in streams
Waterways in the Port Phillip and Westernport Region contain an interesting and diverse variety of fish, with 36 species of freshwater fish (native and introduced) found in rivers, lakes and wetlands and several other species in estuaries. Due to declines in abundance, several of these species are of national conservation significance (such as Dwarf Galaxias and Australian Grayling).
Fish also play an important role as a recreational value, with the Macquarie Perch, Murray Cod and River Blackfish highly valued by the fishing community.
Fish depend on rivers, estuaries and wetlands in several ways. They rely on variations in natural water flows, including floods or 'freshes', to trigger breeding, spawning and migration. A large number of species, such as Australian Grayling and the Short-finned Eel, need to be able to move between the ocean and freshwater habitats to complete critical stages of their life cycle, such as breeding. The structure of waterways is also vital to fish because they need deep pools for resting, undercut banks and logs under which to hide, and streamside vegetation as an important food source.
The current status of fish in each catchment is determined through a combination of survey data and habitat suitability modelling for freshwater species.
The overall score for native fish is moderate, with the Lower Dandenong Creek and Eumemmering Creek sub-catchment being assessed as high – which is largely a reflection of the extent of barriers to fish movement throughout the catchment that prevent some species from reaching other parts of the catchment.
There are 12 freshwater species, 9 exotic species and several estuarine species, including black bream and yellow-eye mullet. Nationally-significant species include the dwarf galaxias.
The overall score for fish is moderate.
There are 13 native and nine exotic freshwater species. Threatened freshwater species include Australian grayling, Yarra pygmy perch and the Australian mudfish.
The overall score for fish is moderate.
There are 21 freshwater species, 13 of which are native. This includes recent records of nationally-significant Australian grayling in the lower Werribee River. There are also several estuarine species, including black bream, yellow-eye mullet, estuary perch, and small-mouthed hardyhead.
Scores for native fish vary from low to very high, with higher-rating areas including the Cardinia Creek, Bunyip River and Lang Lang River.
There are 18 native freshwater species and eight exotic species recorded in the catchment. Nationally-significant species include dwarf galaxias, Australian grayling and Australian mudfish. The catchment supports several estuarine species, including black bream, yellow-eye mullet, estuary perch and pale mangrove goby.
Scores for native fish range from very high and high along the Yarra main stem and in the Little Yarra and Hoddles Creek sub-catchment, to very low in some tributaries in other parts of the catchment.
There are 16 native fish species, including the nationally-listed dwarf galaxis, Macquarie perch (introduced), Australian mudfish and Australian grayling.
- Barriers to movement
Artificial barriers (e.g. weirs, dams, pipes and concrete channels) can restrict the movement of fish along waterways. This is especially problematic for migratory native fish that need to move between freshwater and estuarine or marine habitats to complete their lifecycle.
- Introduced plants and animals
Includes aquatic and terrestrial weeds, and pest fish such as carp and eastern gambusia.
- Water flows
Many fish require ecological triggers such as changes in water flow for natural processes such as mating and spawning to occur.
Increased hard surfaces (e.g. roads, roofs, footpaths, carparks) that directly drain to waterways can dramatically alter the hydrology of receiving waters, leading to poor water quality and changes in waterway stability. The new waterway form has less suitable habitat for fish and the food sources they rely upon (e.g. macroinvertebrates).
- Land practices
Includes vegetation clearing, loss of floodplain habitat, the use of herbicides and pesticides, stock access to waterways.
- Structure and function of waterways
Physical changes to the form of waterways such as channelling, water extraction for domestic and agricultural use, changes in the flow of water, loss of habitat in the waterway and pollutants.
Potential management actions
- Catchment management
Capture, treat and re-use urban stormwater and improve forestry and agricultural land management practices to reduce water quality impacts on waterways.
- Improve connectivity
Reconnect waterways by removing physical barriers and improved flows.
- Protect, enhance and maintain channel habitat e.g. revegetate streamside zones, introduce woody debris to provide fish habitat, control weeds and protect physical form.
- Improve flow regimes
Provide and protect appropriate flows including environmental flows.
- Reduce introduced species
Manage species that either directly predate on native fish or compete for food, breeding and resting sites.