Technical Reports/Books/Manuals

Environmental DNA (eDNA) metabarcoding was used to detect the presence of Tor putitora (Golden mahseer) in selected streams of Sikkim. Water samples were collected from six sites based on habitat characteristics conducive to the species survival. The collection of samples was followed by filtration of water samples, isolation of the DNA, PCR and sequencing targeting the COI region were conducted under aseptic conditions. The results confirmed Tor putitora presence at two locations (BR-06 and BR-08) with high certainty (>99%) aligning with previous studies on tis distribution in Sikkim. These results indicate that these streams serve as habitats for Tor putitora. These findings highlight the potential of these streams to support mahseer populations, reinforcing the need for conservation efforts to protect these critical habitats from ecological threats like ecological pressures, including hydropower and linear infrastructure development. This study adds to the expending evidence concerning mahseer distribution in Sikkim and highlights the critical need for conservation initiatives aimed at safeguarding its essential habitats by incorporating appropriate mitigation measures. Continued research and long term monitoring are imperative to evaluate population dynamics and ensure the sustainable management of Tor putitora in the region.

Golden Mahseer, Tor putitora is popularly known as ‘Himalayan mahseer’ and it is one of the largest freshwater fishes of India It occurs along the mid-hills stretch of Himalayan region including Shivaliks and part of Terai landscape. Over the years, the golden mahseer populations and their habitats have depleted due to various anthropogenic activities, hence, it is listed as an Endangered species in the IUCN Red List. Due to rapid hydro-power developments in the river valleys, habitats of golden mahseer have been fragmented, which in turn affects the ecology and spawning biology of golden mahseer. In order to, understand ecology, habitat use and movement pattern of golden mahseer, this project was proposed in 2017. The study was carried out in the two river systems of Western Himalaya: Kosi river in Ramnagar and Kolhu river in Kotdawar. To study the movement and migratory patterns of golden mahseer, 11 individuals were tagged with radio telemetry tags in the month of June (before onset of monsoon) to understand the migratory behaviour of tagged individuals. Manual tracking and monitoring were performed for all the tagged individuals to get location points and to generate movement data during the period from June-October, 2019. Correspondingly, information related to the fish habitat-type, depth, velocity, temperature and weather was collected. Simultaneously, habitat inventory was performed in three zones in both the rivers; upper, middle and down streams. At each zone 200-meter stream reach was selected for assessment of habitat availability, habitat use by different life history stages of golden mahseer (fingerlings, juveniles and adults). This study was performed for three seasons: Post-winter (March-April), Pre-monsoon (May-early June) and Post-Monsoon (October-November) during 2018-2019. Adults of the golden mahseer were mostly found in deep waters (> 2 m) with cool temperature (18-23o C) and low water velocity (0-0.4m/s). Adults prefer pool habitats with sand and gravel/cobbles as the dominant substratum. Similarly, availability of juveniles and fingerlings were recorded along the river basins and mapped to see the available nursery grounds of the golden mahseer. Habitat preference and microhabitat use were analysed for the available nursery grounds. The results for both the rivers exhibited backwater pools, secondary channels and run habitats as highly used habitats of fingerlings. And, run habitats were mostly as used habitats by juveniles in these rivers. Fingerlings were mostly seen at depth ranges (0.1-0.6m) with velocity (0-1.2m/s) where dominant substratum was gravel and sand. Similarly, depth range between (0.3- >1.8m), moderate velocity (0.3- >1.2m/s) and habitats with cobbles, bed rock and gravel as substrate were used by the juveniles. Based on the habitat availability and use by golden mahseer, Habitat Suitability Curves (HSC’s) for the youngs were formulated. The study revealed that variation in the habitat use by the fish, significantly varied during the monsoons. In the present study, we also recorded other fish species co-existing with golden mahseer in Kosi and Kolhu. Various threats which harm the golden mahseer population and their habitats in Kosi and Kolhu river were recorded and possible conservation measures are discussed

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