Economic and environmental impacts caused by tilapia

Australia has been classed as one of the world's six major hot spots for fish invasions. 

Tilapia (Oreochromis mossambicus) is a major emerging pest threat that has currently established in river and dam systems in Queensland and Western Australia and threatens to spread throughout tropical and sub-tropical Australia, including estuarine environments and the northern Murray-Darling Basin.   They are listed in the World Conservation Union's 100 of the World's Worst Invasive Alien Species.  Tilapia is a declared noxious fish species in Queensland.

Tilapia can reach extremely high densities.  A mass of  tilapia killed using fish poison at a golf course in Port Douglas caused a layer of dead tilapia that was nearly a metre thick in some places, with a total estimated mass of 13 tonnes (see image at right).  At these densities, the species becomes stunted, so has little value as a recreational fishery.

Tilapia compete with and displace native fish species.  They prey upon their eggs and fry, as well as the myriad small invertebrates that form the basis of many native species' diet.  This invader is therefore seen as a major threat to commercial and recreational fisheries in North Queensland and the Northern Territory where native species, especially those dependent upon coastal wetlands, are impacted by this predation and competition for food and habitat - the most notable being prawns and barramundi.   This threat has complicated water management schemes in the north and required investment in multi-million dollar infrastructure to reduce the likelihood of tilapia spreading.

As it spreads, tilapia will impact the endangered Oxleyan Pigmy Perch (Nannoperca oxleyana) and the vulnerable Honey Blue-eye (Pseudomugil mellis) (both listed under the Environment Protection and Biodiversity Conservation Act 1999) and three other fish species listed as threatened by State agencies.

Control options

Currently, tilapia cannot be controlled at anything other than very local scales.  Physical removal, explosives and piscicides are not long-term solutions.  There are too many of them, and they breed too quickly.  Female tilapia can carry eggs in their mouth, and these eggs can survive even if the adult fish is killed.

The main source of spread is still accidental or misguided human introductions, so that the only sustainable and long-term solution has to be a biological control.  No natural biological control agents (parasites or diseases) have been found for the species.   Nonetheless, there is a rising public demand for a solution to the problems posed by tilapia.

New invasion of Tilapia into Gulf catchments

The Queensland Department of Primary Industries and Fisheries officers (DPI&F) are undertaking control activities and have stepped up surveillance in the Gulf region after the pest fish species tilapia was detected in Eureka Creek in January 2008..

DPI&F fisheries biologist Malcolm Pearce said it was most likely the fish had been illegally released in the creek.  They were all juveniles.

Electro-fishing is being used to reduce the population.  Poisoning using the piscicide rotenone cannot be considered in this flowing river system due to the possibility of harming other marine life.  Eureka Creek is a tributary of the Walsh River which flows into the Mitchell River which then flows into the Gulf of Carpentaria.  The area is extremely important to both the commercial and recreational sector, particularly in relation to barramundi catch, and is also a significant breeding ground for other native species.

To report anyone suspected of moving tilapia, or report any sightings of tilapia, contact the Fishwatch Hotline on 1800 017 116  or phone DPI&F on 13 25 23, or  fill out a Pest Fish Report Form online at www.dpi.qld.gov.au/fishweb

Kirsten Phillips, Principal Communication Officer, Fisheries       
Department of Primary Industries and Fisheries
Strategic Communication & Marketing
GPO Box 46 Brisbane Qld 4001

Ph:(07)3224 7757  or  DPI&F 13 25 23 (weekdays 8 am to 6 pm).

More information on our fish projects, visit our Freshwater program pages