Save the Highly Threatened Mysterious Ganges Shark
-Dr. Arvind Singh
The Ganges shark is a rare species of requiem shark found in rivers of north-eastern and eastern India. It is a typical example of ‘River shark’. Ganges shark is a mysterious aquatic fauna because not much is known biologically about it. It is often confused with the Bull shark (Carcharhinus leucas) which also inhabits the Ganges River and thus sometimes referred to as the Ganges shark. The scientific name of Ganges shark is Glyphis gangeticus and it belongs to the Carcharhinidae family in the order Carcharhiniformes. In Bengali, it is known as Baagh maach meaning tiger fish.
Besides Ganges shark, there are five other species of ‘River sharks’. These include Speartooth shark (Glyphis glyphis), Irrawaddy River shark (Glyphis siamensis), Glyphis species A, Glyphis species B and Glyphis species C. All the six known sharks are definitely rare and possibly threatened. Ganges shark is the most familiar among all the ‘river sharks’.
Ganges shark is listed as “Critically Endangered” in the Red List of Threatened Species of International Union for Conservation of Nature and Natural Resources (IUCN). Critically endangered species are those which are facing an extremely high risk of extinction in the wild in the immediate future.
Distribution Range:
The Ganges shark is known only from fresh water habitats, but it may occur in brackish water as well. Ganges shark is largely confined to the rivers of eastern and northeastern India especially the Hooghly River of West Bengal, the Ganges River in Bihar, the Brahmaputra River in Assam and the Mahanadi River is Odisha. It is found in the mid-to-lower reaches of a river.
Physical Characteristics:
Ganges shark is a little known species that are yet to be adequately described. The Ganges shark has a grey to brownish colouration without any discernible pattern or markings. It is stocky with a short, broadly rounded snout and a small wide-spaced nostrils. The eyes are small and dark. Ganges shark has broad, serrated upper teeth. Cusps of lower teeth protrude prominently when the mouth is closed. It has a broad dorsal fin with mid-base closer to the base of the pectoral fins than those of the pelvic fins. Ganges shark has anal fins with a deeply notched posterior margin. The pectoral fins are broad and falcate. A longitudinal upper precaudal pit is present, but the inner dorsal ridge is absent.
The size of Ganges shark at maturity is estimated at about 178 cm, while size at birth is about 56 to 61cm. The maximum size attained by the Ganges shark is estimated at about 204 cm.
Habitat and Ecology:
The habitat of Ganges shark is freshwater and possibly also shallow marine estuaries. The small eyes and teeth of Ganges shark suggest that they are primarily fish-eaters that have adapted to hunting in turbid water of rivers and estuaries.
The eyes of Ganges shark are tilted upward rather than laterally or ventrally as in most carcharhinids, indicating that this species may swim along the bottom and scan the water above it for potential prey back-lit by the sun. Not much is known about reproduction, however, it is probably viviparous.
Are Ganges sharks dangerous to human beings?
Though Ganges sharks are primarily fish eaters they may pose a threat to human beings. However, it has not been established yet. The dangerous reputation of Ganges shark may not be warranted, however, owing to the confusion of Bull shark which occurs in Indian rivers. The Bull shark represents a definite danger to human beings.
Threats to the Survival:
Ganges shark probably exhibits a very slow rate of genetic change making them unable to adapt to anthropogenic environmental changes. Like other sharks, they probably feature life history cycle characterized by long gestation, slow growth and delayed maturity. Hence their populations can be quickly exterminated by even relatively low levels of exploitation such as gillnetting. Thus Ganges shark may be vulnerable to fishing pressure and habitat change.
Ganges shark has been and is currently being fished in the Ganges-Hooghly river system and appears in the international trade in shark jaws as curios and probably also in the oriental fin trade and is consumed locally for its meat.
Besides overfishing, habitat deterioration from pollution, increased river utilization and construction of barrages and dams are the other probable threats to the survival of Ganges shark.
Conservation:
Ganges sharks are extremely rare species known from only three museum specimens, all collected in the 19th century from fresh water in the lower reaches of the Ganges-Hooghly river system. There were no records between 1867 until 1996, although 1996 records have not been confirmed as Ganges shark. Ganges shark was lastly reported in 2001 from the upstream of the mouth of Hooghly River at Mahishadal in West Bengal.
In 2001, the Indian Government banned the landing of all species of Chondrichthyan fish in its ports, though afterwards this ban was amended and now Ganges shark is one of just ten species of Chondrichthyans protected under Schedule-I, Part II A of the Indian Wildlife (Protection) Act, 1972 (Government of India, Ministry of Environment and Forests, 2006).
There is a need to evolve a sound Action Plan after reconfirming the status of Ganges shark for the initiation of the conservation process. The Action Plan should include:
1. Assessment of the threats faced by the Ganges shark in its distribution range.
2. Creation of protected areas and restoration of degraded habitats.
3. Strengthening community awareness and participation.
4. Conducting focused conservation efforts in areas where there is an adequate population of Ganges shark.
5. Strict enforcement of the Indian Wildlife (Protection) Act.
Conclusion:
Thus it can be concluded that Ganges shark is a highly threatened aquatic species of animal with narrow distribution range. No, any information is available regarding the population size in its entire distribution range. Hence, there is an urgent need to assess the population size of the Ganges shark in its entire distribution range to reconfirm its status for the initiation of the conservation process.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with an area of specialization in Ecology. He is a dedicated Researcher having more than four dozen published Research Papers in the Journals of National and International repute. His main area of Research is Restoration of Mined Lands. However, he has also conducted Research on the Vascular Flora of Banaras Hindu University-Main Campus, India.
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