Effects of Water hyacinth (Eichhornia crassipes Solm) Infestation on water quality, fish species diversity and abundance in the Nyanza Gulf of Lake Victoria, Kenya

Abstract

This study compared water quality parameters, fish species diversity and abundance in the water hyacinth infested and non-infested areas. The mean (±SD) water temperature of the infested and non-infested areas were 25.60±4.390C and 24.62±4.940C respectively. Dissolved oxygen 2.44±1.14 mgl-1 of the infested area was significantly lower than non-infested (4.24±0.96 mgl-1) (p<0.05). The mean pH of infested and non-infested areas were 6.05±1.04 and 7.62±0.42 respectively. The lowest (6.97±01.83 mgl-1) nitrate was recorded in infested and the highest (11.34±1.46 mgl-1) in non-infested areas. Infested areas had high fish species diversity (2.00) and evenness (0.93). In the infested areas, Protopterus aethiopicus (35%) had the highest relative abundance, followed by Clarias gariepinus (28%), while in the non-infested areas, Lates niloticus had the highest abundance (23%) followed by Oreochromis niloticus (18%). The abundance of haplochromines, C. gariepinus and P. aethiopicus in the infested areas is attributed to their ability to tolerate low oxygen levels. However, the Lates niloticus is very sensitive to low oxygen levels.