Reservoirs of Sri Lanka and their fisheries
Sri Lanka, a continental tropical island of 65,000 km2, is reputed for its ancient irrigation reservoirs, constructed over the last 2000 years. The island, which is devoid of natural lakes has 3 ha of artificially created lentic waters for every km2. These reservoirs are mostly confined to the dry zone which receives less than 187 cm of rainfall per annum.
The reservoirs vary in age, size, hydrology, catchment characteristics and usage. In the perennial reservoirs the development of fisheries is very recent and is associated with the introduction of the cichlid Oreochromis mossambicus (Peters) in 1952. The inland fishery yields approximately 27,000 to 30,000 tons year-1 and the average production of the perennial reservoirs is estimated to be 283 to 307 kg ha-1 year-1, with a range of 40 to 497 kg ha-1year-1, based on natural recruitment of these fish stocks.
The strategies for optimization of the yield from perennial reservoirs are different from those for seasonal reservoirs, which are small reservoirs that tend to dry out for three to four months a year. The latter group of reservoirs accounts for about 30% of the known total reservoir surface area on the island, and fisheries depends on regular stocking of fish, largely carps.
This study reviews the development of the fishery and its management and the biology of the constituent species. The possibility of using the Sri Lankan reservoir fishery as a model for tropical reservoirs is discussed.