Introduction

Farmed shrimp is a cash crop that earns valuable foreign exchange to Sri Lanka, even though it contributes to only two per cent of world production. According to reports of the Department of Customs, shrimp exports accounted for 50 per cent of the total fisheries exports from Sri Lanka in the late nineties. The rapid growth of the industry in Sri Lanka which is concentrated in the North Western Province of Sri Lanka, has been mainly owing to initiatives of the private sector with no government support (Rohitha, 1997). Global shrimp production has grown at a phenomenal rate of 20–30 per cent per year in recent times with countries in Asia contributing to 70 per cent of world production.

The Dutch canal associated wetland system in Sri Lanka has emerged as one of the most economically important wetlands due to shrimp farming. Since the1980s, shrimp farming in the Dutch Canal has rapidly developed without any planning or coordination (Rohitha, 1997). There are more than 1300 farms covering a land area of 3750 hectares (Siriwardena, 1999) while 48 per cent of the farms (covering 40 per cent of the developed area) are illegal and unauthorized. The haphazard development of the industry has resulted in high eutrophication of the lagoon system contributing to a decline in the shrimp industry's output as well as a decrease in the lagoon's fish harvest. The shrimp industry faces frequent disease outbreaks resulting in low productivity, which could be mainly attributed to the self-imposed pollution of its source of water.