**3. Methodology**

To know the status of key aquatic fauna in the Girwa River, a vessel-based visual survey from Indi-Nepal border to Girijapuri Barrage (N 28° 33′.875; E 81° 12′.981) including the section of Kauriala River (N 28° 28′.640; E 81° 08′.308) in Katerniaghat Wildlife Sanctuary (**Figure 1**) was conducted in a ca.18 km of the river during 8th to 9th February 2013. The survey was conducted by using a motorized boat with an average speed of 4-5 km−1 both in upstream and downstream directions. A single transect line close to one river bank only was followed during the survey.

Methods for dolphin survey, estimation of absolute and relative abundance and study of Asian river dolphins, have been considered and described in detail by [2]. In these method two primary observers, one each on the right and left sides of the vessel searched accurately in a 90° one in front of the vessel. Two independent observers positioned behind the primary observers recorded dolphin sightings missed by the primary team. A Global Positioning System was used to record the distance traveled and the geographical coordinates of dolphin sightings. Group sizes were evaluated with a best, high, and low estimate of numbers to incorporate a degree of uncertainty [3]. The low group size estimate was considered a minimum count and the high estimate a maximum count. Estimates of the total number of individuals and of group size were calculated from the "best" estimates of group size, while the high and low estimates were used to evaluate the uncertainty of the observers about the accuracy of their best estimates [18].

During the survey a separate observer searched for gharial, mugger and aquatic birds (in addition to Dolphins) using the naked eye and binoculars [9]. Data were recorded whenever basking gharial, mugger and aquatic birds were sighted. Identification and status of birds was done using field guides [19], and for conservation status and common and scientific names Bird Life [20], was followed.
