* ICLARM is now known as WorldFish Center

Naga - The *ICLARM Quarterly
Vol. 22, No. 3 (July - September 1999)

The Introduction of Exotic Fish in Sri Lanka with Special Reference to Tilapia
E. R. A. de Zylva

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:

Impact of the Introduction of Apple Snails and Their Control in Japan
Y. Yusa and T. Wada

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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