Australia's native fish populations have declined as a
consequence of a number of key threats. These include:
- competition with introduced species for food or
- habitat
- habitat degradation
- reduced water quality (disturbance of sediments or inflows
of
pollutants)
- spread of diseases and parasites
- translocation and stocking of certain species
- changes to flows
- fisheries exploitation.
Australia has been named in an article (
PLoS Biology) as one of the world's six major hot spots for
invasive fish invasions. Presently, there is estimated to be
up to 34 established pest fish species on mainland Australia.
These invaders directly contribute to key threats 1 to 4 above, and
are often the subject of threat 5.
Invasive fish such as the plague minnow and common carp
are now common in many Australian waterways. Carp can
constitute 90% of the fish biomass in some areas. They cause
significant damage to aquatic habitats, with the greatest damage
being caused by their feeding behaviour. Being predominantly
benthic (bottom-feeding) they stir up sediment, decreasing water
quality and causing habitat modification.
Other emerging pest fish threats include tilapia
– considered to be one of the world's worst 100 pests.
They were originally brought in as a tropical aquarium fish, but
have now invaded river and dam systems in Queensland and Western
Australia. As they spread westwards and southwards they
are expected to take a heavy toll on our native wildlife by eating
the eggs and young of prawns, barramundi and several threatened
species.
Australia's rivers and lakes are also in the firing line for
more new fish invasions. The number of exotic fish that have
invaded Australian waters has jumped from 22 in 1990 to at least 34
today. All but one of these new-comers originated from the
aquarium trade. This highlights that people are in the drivers seat
of this problem. Action is urgently needed to educate
the public about the dire effects on our ecosystems caused by the
dumping of unwanted invasive aquarium fish.
The Murray-Darling Basin Commission (MDBC) has developed a
native
fish strategy with a goal of rehabilitating native fish
communities in the Basin back to 60 per cent of their estimated
pre-European settlement levels after 50 years of
implementation. One of the six driving actions of this
strategy is to control alien fish species. The MDBC has
contributing funding to the Invasive Animals CRC to implement a
number of projects aimed at documenting, quantifying and addressing
the alien fish problem.
What are we doing?
Projects within our Freshwater Products and Strategies Program
include:
Identification of 'hot-spots' of carp reproduction in the
Murray-Darling Basin (MDB)
Integrated tagging for determining movement and migration of
carp within the MDB.
Development of a national rapid response plan for new incursions
of alien freshwater fish
Development of sensory attractants for pest fish control
Koi herpesvirus (KHV): its potential as a biological control
agent for carp in Australia.
National and state policy evaluation on the use of genetic
technologies against invasive fish
Review and development of fish biocides and delivery
options.
Tilapia: determining environmental and life-history
vulnerabilities for management.
Validating ageing of carp from sub-tropical parts of the
Murray-Darling catchment
Development of 'daughterless' technology for the control of
invasive pest fish.
We have two demonstration sites involving our fish work:
