Taxonomy
Scientific Names
The most utilised scientific name is Anguilla bengalensis, described by Gray (1831), however there are other scientific names, which are used to describe this species. These are:
Anguilla variegata (McClelland, 1844).
Anguilla arracana (McClelland, 1844).
Anguilla nebulosa (McClelland, 1844).
Anguilla brevirostris (McClellan, 1844).
Muraena bengalensis (Gray, 1831).
Anguilla elphinstonei (Sykes, 1839).
Muraena macrophthalmos (Peters, 1852).
Muraena labiata (Peters, 1852).
Nomenclature of Anguilla bengalansis
English names: The English names for this organism are Indian Longfin Eel, African Mottled Eel the Indian Mottled Eel (Jacoby, Harrison & Gollock, 2014).
African name: Since this eel is found in Africa, the locals have given it the name Africa-bontpaling (Jacoby, Harrison & Gollock, 2014).
Bengali name: In Bangladesh, this is known as Banehara (বানেহারা), Bao baim (বাও বায়েম), Telkoma (তেলকোমা), Boa baim (বোয়া বায়েম), Bamosh (বামোশ) and Bao mach (বোয়া মাছ) (Talwar and Jhingran, 1991).
Indian name: Amongst the Indian river communities, this eel is known as the Thumbi (Orissa), Serampambu, Vellangoo and Porivelangu (Tamil Nadu), Ahir and Aheer (Maharashtra), Maniangal, Ghalu, Aerel and Vilangu (Kerala) and the Malumgulu and Malugu (Andhra Pradesh) (Talwar and Jhingran, 1991).
Morphology of Anguilla bengalansis
According to Rahman (1989 & 2005) this eel can reach a maximum length of 118cm, however Shafi and Quddus (2001) recorded an eel, measuring over 120cm. Its body is long with a dorsally flattened and conical head with tubular nostrils on the anterior aspect of the head and a mouth. The Indian Longfin Eel is known to have a compressed and well-developed tail and no pelvic fins or barbels. It has small, rounded scales, as well as a complete lateral line. This species generally displays a brownish yellow colour and mottled with a dark brownish colour. The juveniles of this species are not mottled and are lighter on their underside, with dark blotches towards the upper part of their body (Galib, 2011).
Geographical Distribution and Habitat
The Anguilla bengalansis is classified as “Near Threatened” on the IUCN Red List (2018) (Jacoby, Harrison & Gollock, 2014), however it is classified as “Vulnerable” in Bangladesh (Galib, 2011). This organism can be found in several countries throughout Asia and Africa, even though its numbers have decreased drastically over the years. The Indian Mottled Eel can be found in India, Bangladesh, Malawi, Pakistan, Mozambique, South Africa, Pakistan, Nepal, Myanmar, Tanzania, Sri Lanka and it has also been recorded in the Arabian Peninsula (Jacoby, Harrison & Gollock, 2014). The Anguilla bengalansis inhabits rivers, lakes, ponds, streams and in its juvenile stages it lives in the sea. It can be found in Bay of Bengal in Bangladesh and in rivers, such as the Padma, Jamuna, Meghna and Brahmapurtha (Galib, 2011). With regards to their diets, juveniles feed on aquatic invertebrates and insects, while the adults feed on fish, such as trout as well as crustaceans (Jacoby, Harrison & Gollock, 2014).
Fecundity and Spawning of Anguilla bengalansis
The Indian Longfin Eel is a Catadromous organism. The latter means that after 10 to 15 years living in freshwater water bodies, the eel migrates to the sea to breed and to die. The leptocephali, which are the larvae of eels, will then reach the nearshore and they grow into minuscule transparent eels. They then enter a freshwater system and the life cycle initiates again. The potential fecundity of this organism is around 100,000 (Shafi and Quddus, 2001).
Threats faced by Anguilla bengalansis
These species face numerous threats and that is why their numbers are depleting. These threats include:
It is commercially sought after for its commercial use in fish markets, in China. In Japan, it is not as popular, since the plain eel is preferred.
In Nepal, this species is facing threats, such as inappropriate fishing practices, pollution, degradation and modification of habitats and due to the construction of dams. Dams are problematic as eels are not able to carry out their catadromous life cycle. This problem has also occurred in Zimbabwe.
In Africa, these organisms are overly fished for subsistence and also sport fishing.
In Bangladesh and India, the problem this species is facing is pollution, due to certain pollutants which are also harmful to humans. Indian Longfin eels captured in the Ganges River, were analysed and the results displayed high concentration of methyl mercury, which are higher than the limits set by the Prevention of Food Adulteration Act.
(Jacoby, Harrison & Gollock, 2014)
How to Conserve the Anguilla bengalansis
In my opinion, the threats these organisms face need to be intensely researched. It is essential that countries which have a depleted Indian Longfin Eel population, should evaluate and manage the fishing sectors to a greater extent. Since these species are catadromous, it would be essential to allocate a fishing season to this fishery. If this is not established, over-fishing will result in a decrease in eel migration and spawning, therefore resulting in the depletion of the population. Protected areas should also be implemented, where no fishing activities should be allowed. It is essential, that communities which carry out subsistence fishing activities, are educated to fish in a sustainable manner, in order to allow the eel to spawn and re-stock its population. If this is not carried out, it would result in the end of the Indian Longfin Eel fishery. Therefore, if precautions are not taken, this will result in the extinction of this eel and several fishing and food traditions.
References:
Galib, S. (2011) Indian Mottled Eel, Anguilla bengalensis bengalensis (Gray, 1831) [online], Available at: http://en.bdfish.org/2011/08/indian-mottled-eel-anguilla-bengalensis-bengalensis/, (Accessed on: 27/11/18)
Gray JE (1831) Illustrations of Indian zoology; chiefly selected from the collection of Major-General Hardwicke, F.R.S., 20 parts in 2 vols. Illustrations of Indian zoology; chiefly selected from the collection of Major-General Hardwicke, F.R.S., Pls. 1-202.
Jacoby, D., Harrison, I.J. & Gollock, M. (2014) Anguilla bengalensis. The IUCN Red List of Threatened Species 2014: e.T61668607A15501445. http://dx.doi.org/10.2305/IUCN.UK.2014-1.RLTS.T61668607A15501445.en. (Accessed on: 27/11/18).
McClelland J (1844) Apodal fishes of Bengal. Calcutta Journal of Natural History 5(18):151-226, Pls. 5-14.
Rahman AKA (2005) Freshwater Fishes of Bangladesh, 2nd edition, Zoological Society of Bangladesh, Department of Zoology, University of Dhaka, Dhaka-1000, pp. 55-56.
Rahman AKA (1989) Freshwater Fishes of Bangladesh, 1st edition, Zoological Society of Bangladesh, Department of Zoology, University of Dhaka, Dhaka-1000, p. 41.
Shafi M and Quddus MMA (2001) Bangladesher Matsho Shampad (Fisheries of Bangladesh) (in Bengali), Kabir publication. Dhaka, Bangladesh. pp. 17-20.
Talwar PK and Jhingran AG (1991) Inland Fishes of India and Adjacent Countries, Vol. 1, Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi-Calcutta, pp. 74-75
Sykes WH (1839) On the fishes of the Deccan. Proceedings of the General Meetings for Scientific Business of the Zoological Society of London 1838 (6): 157-165.
Image References
Image 1: Revolvy (2018) Mottled Eel [image], Available at:https://www.revolvy.com/page/Mottled-eel, (Accessed on: 27/11/18).
Image 2: ECPlaza (2011) Live Indian Mottle Eel, Anguilla bengalensis bengalensis [image], Available at:https://www.ecplaza.net/offers/live-indian-mottled-eel-anguilla-bengalensis_7767619, (Accessed on:27/11/18).
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