ESR 17:201-215 (2012) - DOI: https://doi.org/10.3354/esr00425
Robust abundance estimate for endangered river dolphin subspecies in South Asia
Gillian T. Braulik1,2,*, Zahid I. Bhatti3, Tahir Ehsan2, Babar Hussain4, Abdul R. Khan5, Ashfaq Khan6, Uzma Khan7, Khalil U. Kundi8, Rafiq Rajput9,†, Albert P. Reichert2,10, Simon P. Northridge1, Hussain B. Bhagat9, Richard Garstang2
†Deceased
ABSTRACT: Robust estimates of absolute abundance are vital for management of threatened species, but these have rarely been generated for endangered South Asian river dolphins due to methodological challenges. An estimate of abundance for the Indus River dolphin in 2006 was generated by conducting tandem vessel-based direct counts; conditional likelihood capture-recapture models were then used to correct for missed animals. Group size and sighting conditions were included as covariates, and abundances of the 3 largest subpopulations were estimated as 101 (coefficient of variation, CV = 44.1%) between Chashma and Taunsa barrages, 52 (CV = 14.9%) between Taunsa barrage and Ghazi Ghat, and 1289 (CV = 33.4%) between Guddu and Sukkur barrages. A total of 75.3% of groups were seen by both independent survey teams, and single animals were almost 5 times more likely to be missed than groups of 3 or more. Providing groups can be matched with minimal error, this survey method shows good potential for abundance estimation of dolphins in confined habitat and the shallow rivers of South Asia. Dolphin encounter rates within the Guddu-Sukkur subpopulation (10.35 km−1) are the highest reported for any river dolphin. Direct counts conducted over a 35 yr period, suggest that this subpopulation may have been increasing in abundance, probably due to the cessation of hunting and possible immigration from other subpopulations. The future of South Asian river dolphins is intimately tied to water security in the region, and escalating and competing demands for freshwater mean that the long-term future of South Asia’s river dolphins is uncertain.
KEY WORDS: River dolphins · Platanista · Abundance · Trends · South Asia · Capture-recapture · Pakistan
Full text in pdf format  | Cite this article as: Braulik GT, Bhatti ZI, Ehsan T, Hussain B and others (2012) Robust abundance estimate for endangered river dolphin subspecies in South Asia. Endang Species Res 17:201-215. https://doi.org/10.3354/esr00425
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