Pakistan's Blind Dolphins Dying Out
7/15/97
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Headline: Pakistan's Blind Dolphins Dying Out
Source: The Environment News Service
Date: 7/15/97
Author: Ahmar Mustikhan
Copyright 1997 ENS, Inc.
KARACHI, Pakistan, July 15, 1997 (ENS) - A species of dolphin that is
nearly blind (Platanista Minor), inhabits portions of the murky waters of
River Indus. The blind dolphin is found only in Pakistan's two provinces -
south-eastern Sindh and north-eastern Punjab. Today, experts say the blind
dolphin, also called Susu, is regarded as one of the world's most
threatened species among the cetaceans - that is whales and dolphins.
The blind dolphin inhabits fresh, rather than ocean waters, and it is
almost completely blind. A deep fold just above the dolphin's mouth is the
remnant of what might once have been eyes down the evolution line.
The 1790 mile (2,864 kilometer) long Indus river has its source in Manswera
Lake at the foothills of the Himalayan mountains. During the last century,
the blind dolphin was found in the entire river system, including the Hindu
holy Ganges River and the Brahmaputra in India. Today, in Sindh its numbers
have dwindled to only 450 dolphins.
The blind dolphin is almost sightless because the waters of the River Indus
are laden with silt and very little light penetrates below the surface, so
this species of dolphin has evolved without a well-developed
light-sensitive organ.
As if by way of natural compensation for the lack of eye-sight, the blind
dolphin has a highly developed sonar system. Since it needs to navigate the
murky waters, nature has endowed it with highly sophisticated navigation
system that depends on sounds and echo location to sense what is taking
place in the surrounding waters.
The blind dolphin, like all dolphins, emits sound energy which boomerangs
as echoes, enabling the dolphin to get a clear and exact picture of what
lies ahead. This system is so highly developed that the dolphin can even
identify the living fishes from the dead ones.
The species has become extinct in large portions of the River Indus in
Pakistan because of an unholy alliance of various factors.
Indiscriminate hunting of the blind dolphins, particularly in the late
1970s, decimated the population.
There has been a sharp decline in the water level as the ecosystem has over
the years been hit by the dams and barrages built to control the water flow
of the River Indus.
The lowering of the water-level led to the division of the dolphin and
their fish prey into a number of smaller groups, isolating them and
retarding their chances of healthy reproduction. The dams and barrages make
the water level unnaturally low during the winter season - when the
Himalayas remain bound with snow - further restricting and limiting the
habitat of the blind dolphins.
Over-use of agro-chemicals such as insecticides, fungicides and herbicides
is yet another factor undermining the health of the blind dolphins'
habitat. Most harmful of all are non-biodegradable pollutants like DDT
which combines with toxins to form even more lethal toxins.
In 1974, the government of south-eastern Sindh province passed a law to ban
the hunting of blind dolphins and the hunters moved north to the
land-locked Punjab province. Later the law was also adopted by Punjab, but
remains to be properly implemented.
Though the blind dolphin is not eaten, oil extracted from its body is used
by local medics to make aphrodisiacs. One local legend has it that the
dolphin was once a woman but a saint cursed it to turn into fish when she
refused to give milk to the holy man.