Does African catfish (Clarias gariepinus) affect rice in integrated rice-fish culture in Lake Victoria Basin, Kenya?

Abstract

An experiment was conducted for 98 days in the Lake Victoria Basin to investigate the interactions of fish and rice growth performance in rice paddies. The experiment was laid out in a split-plot design, with rice cultivar as the main plot and method of rice-fish culture as the sub-plot. Treatments consisted of two levels of rice-fish culture and three cultivars of rice. Rice cultivars used were; ITA, BR 11 and IR 2793-80-1 obtained from the National Irrigation Board (NIB), Kenya. Clarias gariepinus, (15 ± 0.4 g) were stocked at 6 m^-2 and given supplementary diet containing 35% crude protein and 7% lipids at 2× maintenance level. There was significantly less incidence of stem-borers in rice-fish polyculture compared to rice monoculture (P< 0.05). Rice-fish polyculture gave significantly higher rice yield than rice monoculture (453 ± 1.0 gm^-2). The seed yield differed significantly (P< 0.05) between the rice cultivars with ITA giving the highest yield followed by IR and BR. There were significant differences in growth performance of C. gariepinus in the treatments (F = 4.518,df = 2, P = 0.014) with best growth recorded in the Fish-ITA and least in Fish-BR. Mean net annualized fish production was highest (3,767 ± 300 Kgha^-1yr^-1) in the ITA-Fish plots with no statistical differences recorded between BR-Fish and IRFish plots. Fish survival ranged from 79.9 to 82.6 percent in Fish-IR, Fish-BR and Fish-ITA respectively.

Key words: African catfish, rice-fish culture, rice yield, fish yield.