TILAPIA: THE FACTS
Gary "Fitzy" Fitzgerald
Due to recent articles in some publications, I felt it was needed to clear up some of the facts and maybe some of the fiction surrounding Tilapia. Commonly referred to the rabbit of Queensland's waterways Tilapia are part of the Cichlid Family of fishes and come from the warm, fresh and brackish waters of Africa, Sri Lanka, Southern India and parts of the Americas.
They are classified in Queensland as an exotic pest fish and are declared noxious (meaning harmful and unwholesome to the environment). There have been over 100 species of cichlids imported into Australia for the aquarium trade and a few have subsequently been released into the wild and have established breeding populations, Tilapia are just one of these. The main three species are the Mozambique Mouth-brooder (Oreochromis mossambicus) and the most commonly found, the Convict Cichlid (Cichlasoma nigrofasciatum) and the Black Mangrove Cichlid (Tilapia mariae), with the Pearl Cichlid and the Jewel Cichlid being found in small isolated pockets. Anglers generally refer these to as Tilapia.
The Mozambique Mouth-brooder as its name states carries their eggs in the female's mouth to incubate them for a 3-5 days period after which they remain there for another 10 - 14 days after hatching. Although fish that do this don't usually have many eggs they ensure a high survival rate although they can breed several times a year. Juveniles may also live for some time in the female's mouth even after she has died. I have been told that Tilapia eggs can survive for over a month high and dry up the bank or in the freezer, only to again be liberated by rising water levels or the frames used as bait. This is why Tilapia must never be thrown back into the water or even put into the crab pots or crayfish traps as bait.
Except for when they are small these invaders have no natural enemies, as they can grow too large for native predator fish such as bass and even cod to eat. Having a strong resistance to diseases and a high tolerance for salinity and oxygen they thrive in our warm climate being able to survive between 8 and 42 degrees Celsius. There have been odd occasions in impoundments where Tilapia have partially died off after a turn over of the water during winter with westerly winds causing the temperature to fall too low for them to survive. A simple requirement for food means that they can eat almost any thing that is available and compete directly with Australian native fish for food and space and even eating the native fishes eggs. (That is one advantage of being mouth-brooder). Found in habitats such as impoundments, rivers, streams, farm dams, artificial drainage channels and the upper sections of tidal waters, tilapia have the ability to move from one river system to another.
The areas where Tilapia have established themselves include Lakes Wivenhoe, Somerset, Kurwongbah, Tingalpa Reservoir and adjoining waters in south east Queensland and around Townsville, Innisfail, Cairns, Port Douglas and Atherton Tablelands in the north. They have also been recently detected in Boondoomba Dam. There is also a population in Victoria at the Hazelwood power station cooling ponds and the creek below. In the United States Tilapias are a pest as well, but some hybrids have been put to good use in keeping artificial irrigation drains clean with some success.
There are only a few options available to control unwanted invaders. They include poisons (piscicides) specific to fish as was used in a Port Douglas pond in 1989 where FIVE (5) fish were released and turned into over one million fish (18 tonnes) in three years. The downfall of using this is all fish, invertebrates and crustaceans in the particular waterway poisoned will be destroyed.
Another option is stocking of massive amounts of Australian native predator fish such as Barramundi, Mary River Cod and Bass in the hope that they may keep numbers down, noting that tilapia managed to get a foot hold at lake Wivenhoe SE Qld where there are literally millions of fork-tailed catfish present (another mouth-brooder).
The final option is by catching them. But, under the Fisheries Act 1994 "it is an offence to bring noxious fisheries resources (meaning fish) or cause noxious fisheries resources to be brought into Queensland; or possess, rear, sell or buy noxious fisheries resources; or relate noxious fisheries resources; or cause noxious fisheries resources to be placed or released, into Queensland waters. This includes keeping them in an aquarium or farm dam. Fines of up to $150 000 can be imposed on anyone having noxious fish in their possession without a permit. Noxious fish cannot be kept, hatched, reared or sold. When caught all noxious fish should be destroyed; they must not be returned to the water and must not be used as bait. Anyone releasing noxious fish may be charged with the cost of eradication and removal of those fish." It is advised that if any tilapia is caught they should be buried above the high watermark.
The plain fact of the matter is that on any given day there are hundreds of people who go out and target tilapia to eat as it is held that they are quite edible. They are breaking the local law and could face the consequences if caught. But it seems this is the only way that numbers are being kept down. In saying that, it needs to be emphasised that anyone who puts tilapia or any noxious fish into a body of water anywhere is a bloody idiot. I hope this has cleared the water some in regard to Tilapia. For further inquiries contact your local Fisheries office.
List of noxious fish
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