| Naga
- The *ICLARM Quarterly
Vol.
22, No. 3 (July - September 1999)
Features
The
Introduction of Exotic Fish in Sri Lanka with
Special Reference to Tilapia
E.
R. A. de Zylva
Abstract
Introductions
of exotic finfish between 1948 and 1953 are reported
in this paper, with a brief reference to earlier
and later introductions. Exotic fish were introduced
principally to develop the potential for aquaculture
in fresh and brackish waters in order to increase
the availability of fish for rural communities
through the biological control of aquatic vegetation.
The algal feeding tilapia has created a new food
industry in inland and brackishwaters. It has
supplemented marine fishery production in a community
where animal protein intake consists mainly of
fish. It is also being cultured in flooded rice
fields and used in the control of malaria. This
excellent table fish has not had any adverse environmental
impact.
E.R.A.
de Zylva is a Fisheries Consultant and Adviser
on Asian aquaculture training and development
programs. Address: 30/70 Kensington Drive, Taradale
4001, New Zealand. E-mail: raydezylva@xtra.co.nz
Impact
of the Introduction of Apple Snails and Their
Control in Japan
Y.
Yusa and T. Wada
Abstract
The
apple snail, Pomacea canaliculata, was
imported into Japan and cultured extensively for
food in the early 1980s. Not long after, escaped
or discarded snails became feral and started feeding
on rice seedlings and other aquatic plants. This
was especially noted in Kyushu in southern Japan.
Snails are still proliferating, but the area of
damaged rice is not increasing as fast, mainly
because of the success of snail control. Currently,
the most effective methods of avoiding damage
to rice are keeping water shallow, transplanting
older seedlings and, in some cases, using molluscicides
or repellents. However, these methods have almost
no effect on damage by snail feeding when rice
fields are flooded.
The
apple snail is believed to be the most important
obstacle to the spread of direct-sowing culture
of rice in Kyushu. The Ministry of Agriculture,
Forestry and Fisheries has launched a national
project for the integrated management of the snail
under direct-sowing rice culture. Some recent
results from this project are briefly reviewed
in this paper.
Y.
Yusa and T. Wada are from the Kyushu National
Agricultural Experiment Station, Nishigoshi, Kumamoto
861-1192, Japan.
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