Conservation ecology and phylogenetics of the Indus River dolphin (Platanista gangetica minor)

• Main Author: Braulik, Gillian T
• Format: Dissertation
• Language: English
• Published: University of St Andrews 20.06.2012; The University of St Andrews
• Subjects: Abundance; Cetaceans; Dams; Endangered species; Habitat degradation; Indus dolphin > South Asia > Conservation; Indus dolphin > South Asia > Counting; Indus dolphin > South Asia > Effect of habitat modification on; Indus dolphin > South Asia > Phylogeny; Pakistan; Phylogenetics; QL737.C436B8; Range decline; South Asia; Water extraction; 259

The historical range of the Indus River dolphin has declined by 80% since the 19thcentury and has been fragmented into 17 river sections by construction of irrigationbarrages. Dolphin sighting and interview surveys showed that river dolphins persist insix river sections, have been extirpated from ten, and are of unknown status in theremaining section. Logistic regression and survival modelling showed that low dryseason river discharge was the primary factor responsible for the Indus dolphins range decline.Abundance of the three largest Indus dolphin subpopulations was estimated using tandem vessel-based direct counts, corrected for missed animals using conditional likelihoodcapture-recapture models. The entire subspecies was estimated to number between 1550-1750 in 2006. Dolphin encounter rates within the Guddu-Sukkur subpopulation (10.35/km) were the highest reported for any river dolphin and direct counts suggest that this subpopulation may have been increasing in abundance since the 1970s when hunting was banned.The dry season habitat selection of Indus dolphins was explored using GeneralisedLinear Models of dolphin distribution and abundance in relation to river geomorphology,and channel geometry in cross-section. Channel cross-sectional area was shown to bethe most important factor determining dolphin presence. Indus dolphins avoidedchannels with small cross-sectional area <700m2, presumably due to the risk ofentrapment and reduced foraging opportunities.The phylogenetics of Indus and Ganges River dolphins was explored using Mitochondrial control region sequences. Genetic diversity was low, and all 20 Indus River dolphin samples were identical. There were no haplotypes shared by Indus and Ganges River dolphins, phylogenetic trees demonstrated reciprocal monophyletic separation and Bayesian modelling suggested that the two dolphin populations diverged approximately 0.66 million years ago.Declining river flows threaten Indus dolphins especially at the upstream end of their range, and it is important to determine how much water is required to sustain a dolphin population through the dry season. Fisheries interactions are an increasing problem that will be best addressed through localised, community-based conservation activities.