A Preliminary Account of Larvivorous Fish in the Mwea Rice Irrigation System

An extensive survey was conducted in the Mwea Rice Irrigation System to determine the species composition of the fish fauna and to evaluate their potential for mosquito control. Fish species collected were of Tilapia, Oreochromis, Clarias, Barbus, and Gambusia genera. Predominant species of Tilapia, Oreochromis, and Clarias were found in practically all bodies of water within the system, comprising irrigation canals, ponds, and flooded rice paddies. The affinity of the fish for mosquito larvae was evaluated using samples of Tilapia zilli (Gervais) and Oreochromis niloticus (Linn.) and larvae of Aedes aegypti (Linn.). These species showed marked interest in a mosquito larval diet over a wide range of water temperature and pH; optimum temperature and pH for feeding was 25°C and 7.0, respectively.