Spatio-Timporal Variation in Fish Assemblage Structure of Upper Rapti River, Mid-Western Nepal
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Department of Zoology
Abstract
The spatial and temporal variations of fish assemblages in Nepalese rivers and streams is
poorly known. The fish community and environmental factors of the Upper Rapti River
were studied four times a year, spanning all seasons (summer, winter, autumn, and spring).
The fish were agglomerated using a cast net with the assistance of local fishermen from
three sample stations encompassing 15 kilometers. The current results indicate that the
Upper Rapti River is habitat to 12 species representing 2 Orders, 4 Families, and 9 Genera.
The most contributory fish species recorded from Upper Rapti River was Barilius
bendelisis (18.34%) followed by Schizothorax plagiostomus (17.22%) and Schizothorax
labiatus (15.31%). Kruskal-Wallis test was applied where p-value was observed 0.068
among seasons and 0.266 along stations so there was no significant difference in the
abundance of fish among stations and seasons. Physical and chemical variables have a
significant role in determining the condition of the fish community. Throughout a year, the
mean Shannon-Weiner diversity index was 2.2 and species richness was maximum 2.2
during spring and least 1.6 during autumn. With a mean score of 0.9, species evenness was
almost identical in all seasons. The RDA results showed that environmental elements such
as pH, total hardness, free carbon dioxide, DO, and water temperature influence the fish
community structure of the Upper Rapti River. The cluster analysis shows that the
associations between fish assemblages and abundance of fishes. The research might
contribute to the preservation of locally adapted fish in the Upper Rapti River as well as
the advancement of information about the diversity of fish in Nepal.