Very little research effort has been directed towards fish production, either through capture fisheries or aquaculture, in irrigation canals.
Open canals, whether lined or unlined, are suitable for fish production. There are, however, a number of inherent engineering/management problems in many irrigation systems. Generally these are detrimental to fish growth and production. Tubewell irrigation projects and pressurized pipe irrigation systems are not suitable for fish culture (except where the pipe system is fed from an open main canal).
Cage and pen culture are the most suitable forms of aquaculture in irrigation canals.
The efficiency of water use in irrigation systems could be substantially increased by fish production in the irrigation canals. Income from fish production could supplement charges for irrigation water.
There is some potential for the management of irrigation canals as capture fisheries, although this option is unlikely to be as successful as aquaculture. There are no suitable models for predicting potential fish production, and upon which management decisions can be based.
Fish could be profitably and successfully reared in irrigation canals to control unwanted aquatic weed growth. Grass carp is the most thoroughly investigated example, and aside from being a very effective agent of weed control, it is a popular food fish.
There is some potential for the use of fish to control vectors and hosts of water-borne diseases in irrigation canals. Suitable management strategies to maintain sufficient populations of fish for effective control need to be investigated.
Brackish water associated with irrigation schemes can be used for fish production, providing a suitable species is available. Tilapias and some estuarine finfish, and certain Crustacea, are likely candidates.
Canals fed from epilimnetic reservoir waters are likely to be more productive in terms of fish production than those fed by hypolimnetic waters.
Levels of pesticides in fish tissues cultured in irrigation systems could be a constraint to the development of foodfish production in irrigation canals.
Aquatic weeds in irrigation canals may be of positive benefit where they can be harvested and used, directly or indirectly, as fish food.
The legal and socio-economic implications of fish production in irrigation canals need to be addressed to ensure successful development of this resource.
Perhaps the major constraint to aquaculture development in irrigation canals is that a continuous, preferably constant, flow of water is required throughout the culture period. This is not available in many irrigation systems.
