What is it about?
We conducted Nepal’s first environmental DNA (eDNA) based fish biodiversity assessment in two major river systems- Karnali River (KR), which is still pristine and Trishuli River (TR) with numerous hydropower plants. The eDNA was concentrated by filtering (0.45 μm pore size) two liters of water collected at different sampling points in each study site. A total of 224 eDNA samples (KR = 162 and TR = 62) were collected, from which fish species were identified by 12S rRNA metabarcording approach utilizing Illumina sequencing platform. Alpha and beta diversity of species between two river basins were compared. Also, in KR site, fish (N = 795) were caught, and identified using COI gene based DNA barcoding method- building Nepal’s first fish DNA reference database. Field sampling identified 21 species through morphology and DNA barcoding, where Barilius spp. and Schizothorax spp. were the most abundant. From 244 eDNA samples, 24 Operational Taxonomic Units (OTUs) were identified in TR and 46 in KR with 19 being common to both sites, 27 being unique in KR, and five in TR only. Most fishes were of Cypriniformes and Siluriformes orders, with Barilius spp. and Schizothorax spp. being the most abundant. Long distance migratory fish (Tor spp, Neolissochilus hexagonolepis) and non-native fishes were identified in eDNA samples as well. Alpha diversity in TR was significantly lower than in KR.
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Photo by Hunter Brumels on Unsplash
Why is it important?
Although over 180 freshwater fish species have been reported from Nepal, little is known of their ecology and distribution. This information is needed because their diversity may be threatened by developments like hydropower constructions. Our study demonstrated the utility of eDNA as a non-invasive technique for biodiversity assessment which is particularly useful in areas like Nepal with scarce data on fish species distribution.
Perspectives
A story about two Himalayan rivers- one of the most consequential research that we have ever conducted. This was a cumulative result of 5 years of effort and several projects. We have to be extra careful in our developmental efforts, so as not to destroy our nature.
Dr Dibesh Karmacharya
Center for Molecular Dynamics Nepal
Read the Original
This page is a summary of: Environmental DNA (eDNA) based fish biodiversity assessment of two Himalayan rivers of Nepal reveals diversity differences and highlights new species distribution records, PLOS Water, June 2023, PLOS,
DOI: 10.1371/journal.pwat.0000099.
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