Abstract
Information is given on the population status, distribution and ecology of the Ganges river dolphin, Platanista gangetica, in the Karnali River, Nepal. Seven animals were counted. Sightings were highly habitat-specific. Six habitats were identified and classified as primary or marginal, according to differences in physical characteristics and sighting frequencies within them ( χ 2, p < 0·05, d. f. = 5). Mean sighting frequencies were 0·57 and 0·13 sightings/visit for primary and marginal habitats, respectively. Primary habitats were characterized by an eddy counter-current system in the main river flow caused by a fine sand/silt point bar formed from sediment deposits of a convergent stream branch or tributary. Marginal habitats were characterized by a smaller eddy counter-current system caused by an upstream meander. Mean group size was 1·38 animals. Dolphin movements within primary habitats were found to be nonrandom and aggregate for 25 theodolite tracking sessions ( χ 2, p < 0·05, d. f. = 1–7), concentrated in locations of high prey availability and reduced flow. Human disturbance effects are summarized. Recommendations are given for preservation.
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