Fisheries in reservoirs in the arid and semiarid zones of Asia

Waters abstraction for irrigated agriculture is a common practice worldwide. It is estimated that in the year 2010, 45% of the total global food production will come from irrigated lands. In developing countries 80% of water, or even more, may be used for irrigation. Many of today's over 36,000 existing dams serve to store water for irrigation. The impact on fish stocks of damming rivers is well known: the riverine fish stocks in dammed rivers decline and in the best circumstances are replaced by fish species of standing waters. The largest demand for irrigation is in arid and semiarid countries. It is there that the species diversity of native fish has most drastically declined, this being mostly accompanied by a decline in fish yields. In regulated rivers, where much of the water is diverted for irrigation, in order to rehabilitate fish stocks and fisheries and then to maintain sustainable yield, fishery managers have been translocating or introducing fish species, in same instances with their fish food organisms. Regular stocking of hatchery produced fingerlings has become a routine in many irrigation reservoirs. Where an increase in water salinity resulted from discharges of drainage waters and high evaporation. more salt-tolerant fish species have been stocked. While some countries of Central Asia have gathered considerable experience with the management of freshwater fish stocks in a diversity of irrigation water bodies, other arid and semiarid countries in the region still need to introduce sound management practices which would result in an efficient and full utilization of irrigation reservoirs, irrigation canals and residual water bodies for fish production. This paper briefly reviews the major achievements and challenges facing fisheries managers in such countries.