Conservation and biomonitoring in the Vikramshila Gangetic Dolphin Sanctuary, Bihar, India

Abstract

From March 2001 to December 2003 eight direct count surveys in an upstream direction were conducted for Ganges river dolphins Platanista gangetica gangetica in the Vikramshila Gangetic Dolphin Sanctuary, a c. 60 km long segment of the middle Ganges River in Bihar, India. The mean number of dolphins recorded during upstream surveys was 119.4±SD 31.8 (range 88–174), with an encounter rate of 1.8 dolphins km−1 (range 1.4–2.8). During these surveys a rich diversity of other threatened aquatic wildlife was also documented, including the Indian smooth-coated otter Lutrogale perspicillata, gharial Gavialis gangeticus, a variety of freshwater turtles, and 135 water bird species. An assessment of fisheries documented 76 fish species of which 43% were caught exclusively in monofilament gill nets, a gear known to kill dolphins by entanglement. Eight new records of fishes preyed upon by Ganges river dolphins were identified from the stomach contents of two dolphin carcasses (Setipinna brevifilis, Osteobrama cotio cotio, Puntius sophore, Crosochelius latius, Mystus cavasius, Heteropneustus fossilis, Macrognathus pancalus, Sperata seenghala). These fishes and other species previously recorded in the diet of the dolphins composed 33.3% of the total catch sampled in 2001–2003. Interviews of 108 fishing households revealed that literacy rates were low (29.9%) and almost 50% earned less than USD 411 per year. The most important conservation actions that could be taken are for national and state governments to establish civil control and promote the development of community-based fishing cooperatives. These cooperatives could enjoy ownership rights to certain river segments in exchange for employing sustainable fishing techniques that are less injurious to dolphins.

An inventory of mammals, birds and reptiles along a section of the river and banks of upper Ganges, India

“…The probable reasons for fewer bird species encountered may be attributed to seasonal migration in some species which requires a year round sampling effort or cryptic nature of certain species which needs intensive and repetitive surveys for detection, which could not be addressed in this study. The encounter rate for Ganges River Dolphin in the entire stretch was similar to the estimate (0.23) in the Lohit River, eastern Assam (Wakid 2005) but lower than our estimate (0.52±0.068) for a small stretch of 28km between Narora and Anupshahar (Bashir et al 2010b), 0.44 in the Brahmaputra River, Assam (Mohan et al 1997) and 1.8 in Vikramshila Gangetic Dolphin Sanctuary (Choudhary et al 2006). Our results also confirm Brown Roofed Turtle as most abundant turtle Behera (1995) but not recorded in the present surveys; + New additions to the list RC = river course, I = islands, RB = riverbeds, BC = bank cliffs, M = marshlands, A = agricultural fields, F = dense forests along banks.…”

Ganges River Dolphin: An Overview of Biology, Ecology, and Conservation Status in India

“…The river is productive due to the seasonal flood pulse that brings adequate nutrients and has reduced velocity due to its low gradient (1300:1) (Sinha and Prasad 2012). A mean encounter rate of 1.8 dolphins/linear km was reported for the Vikramshila Gangetic Dolphin sanctuary (Choudhary et al 2006) in the middle of the Ganges River. In November 2012, our team recorded an average density of 2.3 dolphins/linear km in the sanctuary and 1.6 dolphins/linear km in the 525-km stretch of the middle Ganges between Sahibganj and Chausa.…”

“…Nearly all reports, however, are qualitative. A few studies reported that preferred habitats in rivers include downstream of shallow and narrow areas (Kasuya and Haque 1972), in narrow and deep sections of rivers (Pilleri 1970), in deep locations where the current is weak (Pilleri and Zbinden 1973-74;Bairagi et al 1997), in deep water pools off the mouths of irrigation canals (Basir et al 2010), near villages and ferry crossings (Pilleri and Bhatti 1982;Sinha 1997), downstream of bridge pilings (Sinha 1997;Smith et al 2001;Choudhary et al 2006), downstream of sand bars and sharp meanders, near bathing ghats, cremation ghats (Sinha 1997), and in channels with muddy and rocky substrates (Kelkar et al 2010). The river dolphins preferentially congregate in such locations that are preferred by local fishermen, and the sites with dolphins had a higher biomass of small fish than did areas in which their presence was not recorded (Kelkar et al 2010).…”

Abundance and Prey Availability Assessment of Ganges River Dolphin (<I>Platanista gangetica gangetica</I>) in a Stretch of Upper Ganges River, India

“…It is the only mammalian predator in the Ganges which is exclusively aquatic, and it plays a vital role in maintaining the essential balance of the ecosystem, occupying the apex of the food chain (Behera, 1995). In spite of being a "flagship" species, representing an ecosystem in need of conservation (Behera, 1995;Anonymous, 2006;Choudhary et al, 2006;Behera et al, 2008;Bashir, 2010), its status has become a matter of grave concern over the past few decades (Behera, 2002). As the tiger is to the forest, the dolphin is to the Ganges River because both are important indicator species and have significant roles to play in their respective ecosystems (Singh, 2001).…”