Patterns of diversity and conservation status of freshwater fishes in the glacial fed and rain fed rivers of Eastern Nepal

Assessment of headwater biodiversity is essential for maintaining upstream downstream ecosystem services of rivers. Fish biodiversity assessment was conducted in the headwater tributaries of the glacial-fed Tamor River and rain-fed Kamala River in eastern Nepal. A total of eight sites were sampled. pH, dissolved oxygen, conductivity and temperature were estimated using multi-meter field probe. Standard electrofishing was conducted for fish sampling with two rounds of fishing for 20 min each at site. Catch per Unit Effort (CPUE) was calculated for each sample and the samples were identified in the field itself following standard literature. Unidentified samples were brought to the laboratory for further identification. Descriptive statistics was performed; Species richness, Shannon Weiner Diversity and Simpson’s Diversity Index were estimated. One way ANOVA and an independent t test were performed respectively to look at the variation in fish abundance between seasons and between the tributaries of the Tamor River and the Kamala River. Threat status categories of the fish species was compared with those of IUCN. pH was neutral to alkaline in both the types of streams. Significant variation (p = 0.01) in seasons as well as between two types of headwater tributaries were observed in pH, temperature and conductivity. Temperature and conductivity were significantly higher in the rain-fed tributaries. These parameters were significantly higher during the pre-monsoon and lowest during the winter in both types of streams. A total of 8940 fishes belonging to four orders, 10 families, 26 genera and 34 species were enumerated. Significant variation in Shannon-Weiner Diversity Index (p = 0.015) and Species Richness (p = 0.005) between the glacial fed and rain fed streams with higher values of these indices in the rain fed tributaries. Fish abundance also varied significantly (p = 0.02) between seasons in the Tamor’s tributaries with higher abundance in the pre-monsoon and lowest during the winter. Cypriniformes was the most dominant taxa with Schistura beavani (26.14), Barilius vagra (8.46) and Garra gotyla gotyla (7.63). Schizothorax richardsonii (10.31) and Schistura beavani (47.19) were the most dominant species in the Kamala’s and the Tamor’s tributaries. These findings indicate that fish assemblages reflect the different ecological regimes of the glacial-fed and rain-fed headwaters. The findings of this study contribute to the knowledge of fish diversity and also compliment the threat status of the IUCN fish data. Replication of similar studies encompassing temporal and spatial scales is necessary for the development pf effective conservation strategies.