Biology Reference
In-Depth Information
Direct Catch
Deliberate killing of
susus
is believed to have declined in most areas but some individuals
are still taken each year and their oil and meat used as liniment, as an aphrodisiac and as bait
for catfish. A few cases are recorded in the middle Ganges in Bihar (Sinha et al 2000), in the
Kalni-Kushiyara River of Bangladesh, and in upper reaches of the Brahmaputra River in
Assam, India (Mohan et al., 1997). The magnitude of direct take in recent years is unknown,
but probably not high (IWC, 2000). Based on a report of dolphin poaching in the Ganges in
2001, the Patna High Court (C.J.W.C. No. 5628) intervened and directed both the state
government of Bihar and central government of India to allocate funds for supporting dolphin
conservation efforts in Bihar and to stop poaching of the susu. It created awareness among the
common masses and at the same time forced the government officials to act which resulted in
an apparent decline in directed killings of the dolphins. However much more needs to be
accomplished. Cooperation among regulatory authorities, NGOs and local fishermen will be
essential for advancing science and community based management and conservation of this
species.
Incidental Catch
Entanglement in fishing gillnets causes significant damage to local population numbers.
Accidental killing is a severe problem for Ganges River dolphins throughout their range.
Gillnets are problematic because from an economic perspective their use is of primary
importance to impoverished fishing communities. The primary cause is believed to be
entanglement in fishing gear, most often in nylon gillnets, mainly because the dolphin's
preferred habitat is often in the same location as primary fishing grounds. It is not easy to get
actual estimates of dolphin mortality due to unorganized fishing in the very vast areas of the
Ganges and its tributaries but the problem of accidental killing is expected to worsen with
increasing fishing intensity and use of monofilament fishing gillnets. Regulations of gillnets
should include strictly limiting their numbers and configurations (e.g. five per family with a
mesh size of no less than 24 mm and a length and width of no more than 150 m and 7 m,
respectively, and these numbers may be adjusted if additional families enter the gillnet
fishery) and requiring fishermen to monitor their nets and release dolphin bycatch if
entangled (Choudhary et al., 2006). Incidental killing via boating also occurs, evidenced by a
pregnant female hit and killed by a boat propeller at Patna in September of 2005. Thus,
motorized river traffic is also a threat to Ganges dolphins.
Habitat Degradation
Construction of dams and barrages for hydroelectric development and irrigation in the
Ganges system has fragmented the dolphin population and prevented migrations, thus leading
to the segregation of populations and a narrowing of the gene pool in which dolphins can
breed. These same barriers have also reduced food availability and also drastically altered the
dolphin's habits and habitat. The population above the Kaptai dam in the Karnaphuli River in
Bangladesh disappeared over a period of 6 or 7 years after dam construction. Similarly, the
dolphin population disappeared from the main stem of the Ganges above the Middle Ganga
Barrage at Bijnor (about 100 km downstream Haridwar) after 12 years of its construction
(Sinha, 1999). Dolphins in Nepal are almost extinct in Mahakali, Narayani and Sapta Kosi
due to construction of barrages at their heads at the India-Nepal border (Smith et al., 1994).
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