Dolphins, Whales and Porpoises: 2002-2010 Conservation - IUCN

16. Assess the impacts of reduced water levels on
river dolphins in the Ganges and Indus rivers –
Pakistan, India, Bangladesh, and Nepal
River cetaceans face the same threats as marine cetaceans,
with an important addition: they must compete with humans
for fresh water, the very substance of their physical environment.
Reeves et al. (1991) questioned whether diminishing
water levels in Pakistan’s Indus River would ultimately
result in the extinction of the river’s endemic dolphin population.
This question applies equally to the Ganges (Padma)
river system of India and Bangladesh. Year-round flows
must be sufficient to allow dolphins to move freely between
deep pools (Smith and Reeves 2000b). Abundant water is
also required for maintaining suitable temperature regimes
and for diluting the enormous volumes of pollutants discharged
into these rivers. Water is abstracted from the Indus
and Ganges basins by an extensive network of irrigation
barrages (Smith et al. 2000). Much is also lost to evaporation
from reservoirs. In downstream reaches, additional
water is removed by tubewells and lost through seepage to
recharge groundwater supplies. In the low-water season, the
main channel of the Indus becomes virtually dry downstream
of Sukkur Barrage, and completely dry downstream
from Kotri Barrage to the delta, thereby eliminating dolphin
habitat in the lower reaches (Mirza and Khurshid 1996; G.
Braulik, pers. comm.). During the dry season in India, the
Ganges becomes so shallow below the Gandak and
Ghaghara confluences that people frequently walk across its
main channel (R.K. Sinha, pers. comm.). The insufficiency
of water released downstream of Farakka Barrage means
that there is little or no dry-season habitat for dolphins
between the barrage and the Ganges (Padma)-Brahmaputra
confluence (Smith et al. 1998). It also means that salt water
intrudes 160km farther inland from the Sundarbans Delta
than it did before the barrage was constructed (Rahman
1986), which has probably reduced the amount of dolphin
habitat. Dolphins are probably absent from about 400km of
their previous upstream range in the Yamuna River and
100km of their previous range in the Son River below
Indrapuri Barrage, in both instances because of insufficient
water (Sinha et al. 2000).
The impacts of reduced supplies of fresh water are potentially
catastrophic for river dolphins and humans. This
project should involve a review of the hydrology, bathymetry,
and temperature regimes of the Indus and Ganges-
Padma river systems in relation to the environmental needs
of river dolphins. The participation of a hydrologist familiar
with the alluvial environment of the Indus and Ganges
plains is essential. Results of the study should provide a
baseline for long-term habitat monitoring, and an informed
basis for promoting water use policies that consider the
needs of dolphins and other freshwater organisms.
17. Investigate the status of small cetaceans in the
Indus Delta, Pakistan
Little information is available on marine cetaceans in the
Indus Delta, although Indo-Pacific hump-backed dolphins
and finless porpoises were reported to be common there in
the 1970s (Pilleri and Gihr 1972; Pilleri and Pilleri 1979).
Recent reports indicate that the abundance of finless porpoises
has declined dramatically, but that hump-backed
dolphins are still seen occasionally. Bottlenose dolphins
may also inhabit delta waters. Local declines in cetacean
abundance are thought to have occurred as a result of increased
ship traffic and intensive fishing (Ahmad 1994;
Roberts 1997).
The Indus Delta comprises 600,000ha of mudflats, mangrove
forests, and estuarine channels (“creeks”). It is located
close to Karachi, Pakistan’s largest port, and is heavily
fished by shrimp trawlers and gillnetters (Majid 1988). The
ecology of the delta is threatened by freshwater abstraction
upstream in the Indus, which has reduced incoming flows by
more than 90%. This has caused increased erosion, pollution,
and saltwater intrusion in the delta, thereby threatening
the viability of estuarine and mangrove habitat
(Meynell 1991). There is a need to assess the status of small
cetaceans in the Indus Delta and to evaluate the impacts of
intensive fishing and reduced freshwater input on their populations.
As with most projects in this Action Plan, the
training and involvement of local scientists and use of standard
methods are essential components.
18. Assess the status of cetaceans and threats
from direct and indirect exploitation in Sri
Lanka
Large numbers of cetaceans have been killed in directed
hunts and by entanglement in fishing gear in Sri Lanka
(Leatherwood and Reeves 1989; Leatherwood 1994). A
recent survey of fish landing sites in south-eastern Sri Lanka
recorded 14 cetacean species, dominated by spinner dolphins.
A sizable proportion of the animals had been harpooned,
and it appeared that deliberate hunting was
increasing (Ilangakoon 1997). Although cetaceans were
afforded legal protection at the national level in 1993, there
is almost no enforcement (A. Ilangakoon, pers. comm.). The
lack of reliable data on cetacean populations and mortality
rates makes it impossible to assess the magnitude of the
problem and to establish priorities for conservation.
IUCN’s national office in Sri Lanka has proposed a
comprehensive program to study cetacean populations
and the impacts on them from hunting and fishing activities
in south-eastern Sri Lanka, and to increase community
awareness about the conservation of small
cetaceans in two villages where large numbers of carcasses
have been recorded at fish landing sites (Mirissa and
Kirinda). The CSG has endorsed IUCN-Sri Lanka’s proposal
and urges that the proposed work be expanded to
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