Exotic Aquatic Organisms - International Development Research ...

species for food and space, again leading to poor growth, this time among other species of fish.
By the early 1960's, tilapia began to be regarded as a nuisance.
In a bid to overcome problems inherent in 0. mossambicus culture, attempts were made to
develop all-male hybrids. Hickling (1960) experimented on hybridization and as a result of his
experiments Oreochromis niloticus, 0. hornorum, Tilapia zulu and T. rendalli were introduced
into Malaysia. He was successful in obtaining an all-male hybrid (0. mossambicus x 0.
hornorum), but it did not find lasting commercial success in Malaysia. This is because hybrids
were contaminated by stray 0. mossambicus.
In 1972, the Department of Fisheries officially ceased all production of 0. mossambicus in
its hatcheries. A policy of discouraging its culture was also instituted.
The policy was revised only in 1975, with the recognition of 0. niloticus as an acceptable
alternative. While 0. niloticus was originally brought into Malaysia in the 1960's, pure lines
were not maintained. Therefore, in 1979 a stock of pure 0. niloticus consisting of 400
individuals was imported from Chengmai, Thailand, and raised in the Department of Fisheries
hatchery of Jitra, Kedah. This stock constituted the broodstock for all the Department hatcheries
to the present.
The Department of Fisheries first imported six red tilapia from Thailand in 1981. A second
importation consisting of 500 individuals was made from Thailand in the same year. In 1982, a
stock of red hybrids was imported from Taiwan and maintained in the Freshwater Fisheries
Center, Bukit Tinggi, to prevent interbreeding with wild stock or with each other.
Red tilapia found a lucrative urban market, and before long commercial culture of red tilapia
started. However, soon demand outstripped production by 12.7% in 1983, 22.5% in 1984, 24.7%
in 1985 and 19.6% in 1986.
The industry was also very substantially different from the one that raised 0. mossambicus
thirty years earlier. Tilapia was then raised by small farmers in ponds and mining pools using
semi-intensive and extensive methods. The red tilapia, while still relying substantially on such
methods, saw the proliferation of commercial, intensively operated farms using formulated feeds
and high rates of water exchange.
Markets have also changed. Where 0. mossambicus was sold fresh at the wet markets, red
tilapia is consigned mainly to the restaurant trade which demands live fish. Live red tilapia is
also sold in specific supermarkets under the name red snapper or cherry snapper.
There is little documented evidence of impact of the tilapia in Malaysian waters. The
proliferation of 0. mossambicus particularly in mining pools and lakes, is generally recognized
as having affected local icthyofaunal populations but the species affected and extent to which
they have been affected is not documented. The massive importation of red tilapia fry may have
brought in non-indigenous epizootics. A lack of suitable baseline information on the fish disease
status of the country however, prevents any meaningful comparisons.
Red tilapia (particularly those not treated for monosexuality) are no less prolific than 0.
mossambicus. It is no longer uncommon to see mining pools filled with red tilapia fry and
stunted red fish. These fry have undoubtedly escaped into rivers and streams, where they
proliferate, breeding either with themselves or with wild 0. mossambicus stock. At this point in
time, red tilapia have yet to match the widespread distribution of 0. mossambicus. Whether they
will or not is an open question and will depend on their hardiness and their capability to compete
with resident animals.
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