Exotic Aquatic Organisms - International Development Research ...

Appendix II
Assessment of the Impact of Major Food Fish Species
Introduced into Some of the Asian Countries
The Workshop decided upon five criteria, admittedly not all of them easily evaluable
nor objective, as the most appropriate means of assessing the success of the major food
fish species introductions on the information available presently. The five criteria are as
follows:
the introduced species is self-reproducing in natural waters and/or easily
bred under hatchery conditions in the host country,
the introduced species has resulted in an increase in production,
the introduced species has not been responsible for transmission and/or
introduction of a new disease,
the introduced species has not endangered any of the indigenous fish
species, and
the introduced species has not had any detrimental/deleterious effects on
any waters.
On this basis a total of 58 species belonging to 15 families which are considered as
food fish by each country were assessed, and the details are given in Tables All. 1-9. In
certain instances a species considered as a food fish by one country may not be given a
similar status by another. For example, Oreochromis mossambicus is not treated as a food
fish in Australia and in Singapore. If a species has been introduced to all countries in
Asia under review and is treated as a food fish by all, a total maximum score of 45 is
possible. In this manner, the actual score for each species as a percentage of the
maximum attainable was calculated (Table AII.1O). From the data presented it is
therefore, evident that very few species have had an overall detrimental influence on the
native flora and fauna. Also it should be borne in mind that in certain countries because
of the prevailing socio-economic conditions and cultural preferences a species may be
considered as a 'nuisance' or having a degradatory effect on the native fauna. A case in
point is the role of 0. mossambicus in Indian waters; it is conceded there had been an
increase in production, at least in some waters due to this species, and there is no firm
evidence to show that it has brought about a decline in production or elimination of
native species. In spite of these, the species is categorized as a 'nuisance' species. A
similar trend of thought to be now developing with respect to Chinese bighead carp.
Admittedly, it is difficult to remove these biases entirely, especially when the criteria
of assessment of the success of a species are not fully objective. It is important for the
readers to be aware of these apparent biases.
It is also evident from the assessment tables of individual countries that few food fish
introductions are associated with introduction of parasites and diseases. Most food fish
introductions were made in the 1950's to late 1960's. It may be because a knowledge of
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