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Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal

Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers is low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nep...

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Autores principales: Yadav, Ramesh Kumar, Lamichhane, Saneer, Thanet, Dol Raj, Rayamajhi, Trishna, Bhattarai, Santosh, Bashyal, Ashish, Lamichhane, Babu Ram
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9579734/
https://www.ncbi.nlm.nih.gov/pubmed/36267686
http://dx.doi.org/10.1002/ece3.9425
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author Yadav, Ramesh Kumar
Lamichhane, Saneer
Thanet, Dol Raj
Rayamajhi, Trishna
Bhattarai, Santosh
Bashyal, Ashish
Lamichhane, Babu Ram
author_facet Yadav, Ramesh Kumar
Lamichhane, Saneer
Thanet, Dol Raj
Rayamajhi, Trishna
Bhattarai, Santosh
Bashyal, Ashish
Lamichhane, Babu Ram
author_sort Yadav, Ramesh Kumar
collection PubMed
description Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers is low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 km, and gharials were counted directly with three replicates. Gharial count data were analyzed using an N‐mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119–181), with a mean abundance of 8.3 (SD = 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Similarly, the number of sandbank present influenced the detection probability of gharials. Our study shows that gharial population estimation can be improved using the N‐mixture model. The overall gharial occupancy estimated using single season occupancy model was 0.84 (SD = 0.08), with a detection probability of 0.37 (SD = 0.02). The management authority should concentrate on segments to minimize human disturbance (e.g., fishing, washing clothes, extraction of riverbed materials). If the gharial population in this river declines, their population in central Nepal will be threatened. Hence, we suggest designating the Rapti River section that passes across the CNP as a “no extraction zone.”
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spelling pubmed-95797342022-10-19 Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal Yadav, Ramesh Kumar Lamichhane, Saneer Thanet, Dol Raj Rayamajhi, Trishna Bhattarai, Santosh Bashyal, Ashish Lamichhane, Babu Ram Ecol Evol Research Articles Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers is low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 km, and gharials were counted directly with three replicates. Gharial count data were analyzed using an N‐mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119–181), with a mean abundance of 8.3 (SD = 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Similarly, the number of sandbank present influenced the detection probability of gharials. Our study shows that gharial population estimation can be improved using the N‐mixture model. The overall gharial occupancy estimated using single season occupancy model was 0.84 (SD = 0.08), with a detection probability of 0.37 (SD = 0.02). The management authority should concentrate on segments to minimize human disturbance (e.g., fishing, washing clothes, extraction of riverbed materials). If the gharial population in this river declines, their population in central Nepal will be threatened. Hence, we suggest designating the Rapti River section that passes across the CNP as a “no extraction zone.” John Wiley and Sons Inc. 2022-10-18 /pmc/articles/PMC9579734/ /pubmed/36267686 http://dx.doi.org/10.1002/ece3.9425 Text en © 2022 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. https://creativecommons.org/licenses/by/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Articles
Yadav, Ramesh Kumar
Lamichhane, Saneer
Thanet, Dol Raj
Rayamajhi, Trishna
Bhattarai, Santosh
Bashyal, Ashish
Lamichhane, Babu Ram
Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title_full Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title_fullStr Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title_full_unstemmed Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title_short Gharial (Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal
title_sort gharial (gavialis gangeticus, gmelin, 1789) abundance in the rapti river, chitwan national park, nepal
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9579734/
https://www.ncbi.nlm.nih.gov/pubmed/36267686
http://dx.doi.org/10.1002/ece3.9425
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