**2. Study area**

**1. Introduction**

286 Biological Resources of Water

ments worldwide [1].

0.19 dolphin/km [9].

List [16].

Freshwater ecosystems are fragile environment, are rich in biodiversity and are believed to be at risk than other freshwater animals. To understand the mechanism, driving losses in aquatic biodiversity, is important to the conservation and restoration of freshwater environ-

The Ganges River dolphin is distributed in the Ganges, Brahmaputra, Karnaphuli-Sangu, and Meghna river systems and their tributaries, from the foothills of the Himalaya to the limits of the tidal zone in India, Bangladesh and Nepal [2, 3]. It has already become extinct from most of its earlier distribution ranges and even in its present day distribution range the population is purported to be declining [4]. Extensive population fragmentation has resulted from the widespread construction of dams and barrages [5]. The Ganges River Dolphin however, is a true River Dolphin; it occurs only in fresh water, and is considered endangered [6]. The Government of India declared it as the "National Aquatic Animal" [7] and it has received protection in nine protected areas (PAs); of these the Vikramshila Ganges River Dolphin Sanctuary near Bhagalpur is specifically known for the conservation of the Ganges River Dolphin. They have also received some protection in the Girwa and Chambal River, specially created for the protection of the gharial [8]. In recent years several workers estimated the population of Ganga river dolphin in different segments of Ganga River and its tributaries e.g. In Ganges River ca.1200 km (Bijnor to Varanasi), with an encounter rate of 0.21 dolphin/km. In Yamuna River ca. 400 km (Pachnada-Allahabad), with an encounter rate of 0.07 dolphin/ km [8]. In River Girwa, ca. 18 km, with an encounter rate of 1.56 dolphins/ km. In Ghaghara river with an encounter rate of 0.45 dolphins/km. In Saryu River, ca. 30 km with an encounter rate of 0.51 dolphin/km. In Rapti River ca. 30 km with an encounter rate of 0.26 dolphin/km. However, no dolphin was recorded in Ken river ca. 30 km and Betwa River ca. 29 km [8]. In Chambal river ca. 425 km (Pali-Pachnada), the encounter rate of dolphin was

The north Indian State of Uttar Pradesh includes a large extent of the present day distribution of crocodile species, which occurs in the several large rivers flowing through the State viz. the Ganga [10], the Yamuna [11], the Chambal [11], the Ghagra, the Gandak [12] and the Sone River [13]. Early records reveal that these aquatic reptiles were, at one time, very abundant throughout their distribution range [14]. However, due to commercial exploitation and habitat destruction, populations of Crocodile species have been reduced to near extinction. In many habitats, Crocodile populations have been totally wiped out [15]. Considering their vulnerability, the gharial is now listed as Critically Endangered and the Mugger is listed as endangered on the International Union of Conservation of Nature (IUCN) Red

In Girwa River dolphin prefers to stay in deep water in and around the confluence of rivers, shares its habitat with few indicator species such as crocodiles, freshwater turtles and aquatic birds many of which are fish eaters and potential competitors with dolphins [17]. Studying indicator species could create the basis for a sustained research program to see The Karnali River arises in Nepal and bifurcates into two rivers, the Girwa and the Kauriala which reunites again in India to form Ghagra (WWF-India unpublished, 2001). The Girwa River, in the Katerniaghat Wildlife Sanctuary ca.18 km in length is bounded upstream by the Nepalese border and downstream by the Girijapuri barrage in India (**Figure 1**). The river is home to large aquatic animals such as endangered Ganges river dolphin (*Platanista gangetica gangetica)* (**Figure 2A**)*,* critically endangered gharial (*Gavialis gangeticus)* (**Figure 2B**)., mugger (*Crocodilus palustris)* (**Figure 2C**).*,* Smooth coated otter *(Lutragale perspicillate),* several freshwater turtle species and aquatic birds (**Figure 2D**).

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

Status of the Important Bioresources of Girwa River with Special Reference to Ganges River…

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All sections of the Girwa River were searched both in up and downstream. Certain sections affected by water storage due to the barrage however comprised wide channel. A single transect line close to one river bank only was followed during survey of these sections. The population estimates in these sections could therefore be biased downward. All published and unpublished counts of Crocodile and Dolphin populations are presented in **Table 1**. [21] have reported the numbers of dolphins sighted in two detailed surveys of the Girwa River, one upstream and one downstream, conducted in 19 to 25 February 1994. The low-best-high figures totaled 20-24-29 and 13-15-16 for the two surveys respectively. Basu and Sharma, (Unpublished Report 2000) estimated a population of 25 dolphins for the entire river in the Katerniaghat Wildlife Sanctuary. During 2001, the encounter rate of dolphins in the river based on "best" estimate of 30 dolphins was 1.67dolphins/ km river length. Low-best-high estimates in the river were 23-30-44 (WWF-India unpublished Report 2001). In 2006, the encounter rate of dolphins based on best estimate of 39 dolphins was 1.95 dolphins/ km. The Low-best-high estimate of dolphin in the river was 31-39-54. Based on best estimate in 2009, a total of 49 dolphins with an encounter rate of 2.22 dolphins/km of river length are estimated. The Low-Best-High estimate was 40-49-62 (WWF-India unpublished Report 2009). In 2012, the encounter rate of dolphins was 1.56 dolphins/ km. The Low-Best-High estimate was 29-39-44 [9]. During present survey, the encounter rate of dolphins based on "best" estimate of 35 dolphins was 1.94 dolphins/km river length where the boat was moving at a speed of 4–5 km−1. The Low-best-high estimates totaled 27-35-41 (**Table 1**). Evaluation of status of dolphins in the Girwa River, compared to the best estimates of [21], indicates that in the 23 year period following their work, the encounter rate of dolphins is higher than the earlier population record. During the present survey, dolphins were encountered along the entire length of the Girwa with the exceptions of ca. 1.5 km section immediately below the international border entirely of boulder bed riffles and too shallow (< 0.5 m depth) to be habitable by dolphins and a 2 km section just above the barrage. The effect of water storage by the barrage that became operational in 1975–1976, is perceivable up to ca.

**4.1. Present and past estimates of key aquatic fauna in Girwa river**

10 km upstream of the barrage (WWF-India unpublished 2001).

2013 (**Table 1**).

Earlier count of crocodile in Girwa river was 49 gharial and 14 mugger in 2006, 70 gharial and 16 mugger in 2009 and 65 gharials and 20 mugger in the year 2013 (**Table 1**). The first gharial population survey in Katerniaghat Wildlife Sanctuary was in 1975–1976 followed by [22, 23] 105 individual in 2008 by [24], WWF-India unpublished (2006, 2009) and present survey in

Bird Life [20], was followed.

**4. Results and discussion**

**Figure 2.** Gangetic dolphin \_2A, Gharial\_2B, Mugger \_2C, and Red Crested Pochard\_2D.
