Study of agricultural impacts through fish base variables in different rivers

ABSTRACT

Dominant agricultural society of Nepal demonstrates the sign of compromises on its rural and virgin landscape. The current study investigates the fish base indices on some of its watershed. It is a proven fact that fish base variables such as species diversity and the abundance indicate the extent of impact by various disturbances on the ecological integrity of the river system. Three rivers, namely Jhikhukhola, Rapti and Tinau were studied to see the agricultural impact by taking fish species number and their abundance as the indicators in this work. The study was done for an academic purpose from 2003 to 2006 in which sampling was done using electro-fishing gear by standard wading method. Four replicates of sample taken in four major seasons were obtained in the field. Altogether, 10542 fishes of 24 genera and 34 species were captured during the entire sampling. The comparison of their distribution and abundance showed a clear sign of impact mainly on the downstream of the rivers indicating the rapid increase in unaccounted and indiscriminate use of agricultural inputs such as synthetic fertilizers and pesticides. This was further verified by nonparametric Kruskal-Wallis test which showed the significant variations in the impact on the downstream in major agricultural season