SPATIAL VARIATION IN SOME ASPECTS OF BIOLOGY OF Barbus altianalis(Boulenger, 1900) ALONG RIVER NYANDO, KENYA

Abstract

This study aimed at determining the spatial variation in condition factor and growth patterns, fecundity, gonadal maturity stages and feeding habits of B. altianalis and further correlates its feeding aspects with selected water quality parameters along River Nyando. Three sites S1 at the upper region; S2 at the mid region and S3 at the lower region closer to the river mouth were sampled. Fish sampling was done using an electrofisher and the sampled fish identified in the field. The length and weight of Barbus altianalis were taken in the field to the nearest 0.1 g. The stomachs were gutted and then preserved in vials in 5% formalin for later examination of dietary components; Fresh ovaries were fixed in buffered 10% formalin for 12 hours and stored in 70% ethanol for determination of fecundity. Total weight varied significantly among sites in tandem with variation in TL and condition factor. The highest total weight was recorded at site S1, and the lowest at S2 this could be attributed to food availability where food were more at S1 and water quality which affected fish at S2 due to pollution. Fecundity was found to differ significantly among the sampling locations. Highest fecundity occurred in fish sampled from S1 this could be attributed to the high proportion of females at the station followed by fish sampled from S3 while the least fecundity occurred at site S2. Where there was low proportion of ripe/running females. At all the sampling sites females were significantly higher than males there could be a possibility of sex reversal where males reverse their sex in response to environment another factor could be male mortality due to greater reproductive investment. Ten dietary groups were identified from the guts among the sampling sites. At site S1, ephemeroptera, cladocera and detritus were the dominant food items this was because of its availability in the environment and presence of a higher proportion of mature fish, while S2 were dominated exclusively by insects and diptera and at S3, plant materials, insects and diptera were more dominant. Gastropods plant seeds and algae were consumed by the fish but at low numerical abundance at all the sampling sites due to lack of preference by fish. . There were strong negative electivity for rotifers and copepods by the fish. At site S1, coleoptera and insects were positively selected while at site S2, there was negative electivity for plant materials, and gastropods. At S3, very strong negative electivity was observed for algae, gastropod shells and cladocera with plant materials, coleopteran, plant seeds and detritus having positive selection. Conclusion fish size and condition factor varied between the stations along River Nyando. B.altianalis within the upper region was generally bigger in size compared to those around the river mouth. Based on the results of this study and conclusion above, the following are recommended a size frequency research should be done for this fish in River Nyando over a long period of time preferably two years to ascertain spatial variation of Barbus.