The Elasmobranchii subclass is a group of over a 1000 species of highly unique marine organisms. This is a group that consists of rays and sharks (Compagno, 2001). Most of these organisms have slower growth and later maturity, when compared to teleost fish (Camhi et al., 1998). This has resulted in a very low intrinsic rate of increase and a low resilience to mortalities, due to fishing activities. Therefore, sharks and rays can only withstand a certain level of fishing activities, since if these activities increase and surpass the sustainable level, their will be a decrease in Elasmobranchii populations (Camhi et al., 1998). Hence, it is essential that these organisms are protected.
One of the Elasmobranch species, that is classified as “Vulnerable” on the IUCN Red List, therefore has suffered a depletion in its population, is the Himantura uarnak (Forsskål, 1775). This species is classified as follows:
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Myliobatiformes
Family: Dasyatidae
Genus: Himantura
Species: Uarnak
(Matsumoto, White & Gutteridge, 2016)
Other Nomenclature for Himantura uarnak
There are other scientific names that are used to describe this species. These are:
Raja uarnak (Gmelin, 1789).
Himantura variegatus (McClelland, 1841).
Himantura punctate (Günther, 1870).
There are several English names given to this species, such as Reticulate Whipray, Leopard Stingray, Honeycomb Stingray and Marbled Stingray. In Arabic it is known as the Ruget, while in Malay it is called Pari Harimau and Pari Bunga (Matsumoto, White & Gutteridge, 2016).
Morphology of Himantura uarnak
The Himantura uarnak is a whipray covered in dark spots, over a light brown colour. In the juveniles, the spots are well-spaced, however in adults the spots become more crowded, to form a reticulate pattern. The Reticulate Whipray has a whitish colour on the ventral aspect and its tail is covered in black and white bands. The latter is long and slender, it generally is 3 times the length of the whole body and usually has one medium-sized sting on its tail. The maximum length ever recorded for this species, was a male of around 200cm, with a weight of 120kg (Campagno, 1986 & 1989).
Geographical Distribution and Habitat of Himantura uarnak
The Himantura uarnak is highly distributed throughout the Indo-Pacific oceans, from South Africa to Australia. Therefore, this species can be found in India, Bangladesh, the Arabian Gulf and the Red Sea. This species is also a Lessepsian migrant, as it has entered the Mediterranean Sea, through the Suez Canal. In Australia this can be spotted in Shark Bay and in Brisbane. The Reticulate Whipray can be found in sandy regions, in estuaries and lagoons and it may also cross into freshwater. It can inhabit shallow, as well as, deep waters up to 50m. Himantura uarnak is also classified as a mesopredator and carries out viviparous reproduction. However, this species has a low fecundity, since a female generally possesses 2 embryos (Matsumoto, White & Gutteridge, 2016).
Threats Faced by Himantura uarnak
The Reticulate Whipray is quite popular for human consumption, since it can be used fresh, dried and even salted. In some areas, the flesh of this whipray is sought after for other uses, such as the drying and exportation of the skin, to be used for the manufacture of wallets, shoes, handbags and belts (Matsumoto, White & Gutteridge, 2016).
Saving this Species from Extinction
There are no specific conservation measures for this species. However, in Australia, since the year 2000, all trawlers are legally bound to use bycatch reduction devices, in order to decrease the capture of Himantura uarnak. This has resulted in a significant decrease in the Reticulate Whipray bycatch by 36.3%. Marine Protected Areas in the Indo-Pacific region, have also been implemented to protect these species, such as the Great Barrier Reef Marine Park in Australia and the Swatch of No-Ground Marine Protected Area in Bangladesh (Matsumoto, White & Gutteridge, 2016).
References
Camhi, M., Fowler, S., Musick, J., Bräutigam, A. & Fordham, S. 1998. Sharks and their relatives: Ecology and Conservation. Occasional Paper of the IUCN Species Survival Commission Occas. Pap. No. 20.
Compagno, L.J.V., 1986. Dasyatidae. p. 135-142. In M.M. Smith and P.C. Heemstra (eds.) Smiths' sea fishes. Springer-Verlag, Berlin.
Compagno, L.J.V., D.A. Ebert and M.J. Smale, 1989. Guide to the sharks and rays of southern Africa. New Holland (Publ.) Ltd., London. 158 p.
Compagno, L.J.V. 2001. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Vol. 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO Species Catalogue for Fishery Purposes No.1. Rome. 269 pp.
Manjaji Matsumoto, B.M., White, W.T. & Gutteridge, A.N. 2016. Himantura uarnak. The IUCN Red List of Threatened Species 2016: e.T161692A68629130. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T161692A68629130.en. Downloaded on 30 November 2018.
Image References
Image 1: Pollerspöck, J. & Straube, N. (2018) Himantura uarnak (FORSSKÅL, 1775) [image], Available at: https://shark-references.com/species/view/Himantura-uarnak, (Accessed on: 1/12/18).
Image 2: Manjaji Matsumoto, B.M., White, W.T. & Gutteridge, A.N. 2016. Himantura uarnak. The IUCN Red List of Threatened Species 2016: e.T161692A68629130. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T161692A68629130.en. Downloaded on 30 November 2018.