by - Dave Downie
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.
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
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.
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.
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.
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.
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).
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.
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.
of noxious fish in Queensland.
4- Walking Catfish
6- Electric Eel
7- Grass Carp
8- Largemouth Bass
10- Nile Perch (alive only)
11- Parasitic Catfish
12- Pike Cichlid
14- Tiger Shovelnose Catfish
16- Chinese Weather Loach
2000. Garry Fitzgerald. Sweetwater Fishing Australia