THOOTHUKUDI: In a bid to evolve a conservation plan for threatened species, researchers have urged the need to carry out more research programmes to explore the fish diversity in Thamirabarani river, an ancient water body of the state. At present, the river is home to six endangered species, even as invasive species pose threat for the fish diversity.
The Thamirabarani river, which originates from Podhigai hills, traverses 120 km through Tirunelveli and Thoothukudi districts, before emptying into the Gulf of Mannar along the Bay of Bengal at Punnakayal. It slides down the eastern slopes of Western Ghats for 24 km, along the Tirunelveli and Thoothukudi plains for 56 km and 40 km, respectively. As many as 125 species, including 72 of fresh water habitat and 53 of estuarine habitat, have been recorded in the river.
According to the research paper 'Fishes from Tamiraparani river system, Tamil Nadu' published in the Indian Journal of Animal Sciences, as many as 125 species, including 72 of fresh water habitat and 53 of estuarine habitat, have been recorded in this river. Of this, as many as 80 species are of food value, 32 species of ornamental value, and 13 of both ornamental and food values. Also, over 63 species were recorded in the upstream of Manimutharu, 66 species in the mid-stream, 58 species at Srivaikuntam anaicut, and 53 species at Punnakayal estuary. Due to its location in catchment areas, which receive rains during both southwest and northeast monsoons, Thamirabarani river flows throughout the year. Interestingly, it is the only river in Tamil Nadu to originate and flow through the state, and also holds a perennial status.
In the Thamirabarani river system, the top three orders with diverse species composition are Cypriniformes (43 species), Perciformes (36 species) and Siluriformes (19 species). While six species are endangered, four are vulnerable, besides nine are near threatened, 64 are in the least concern category, three are data deficient and 39 species have not been evaluated against the IUCN criteria. The six endangered species include three ornamental fishes - Dawkinsia arulius, Dawkinsia tambraparniei and Garra kalakadensis and three food species of Hypselobarbus curmuca, Hypselobarbus dubius, and Pterocryptis wynaadensis, sources said.
HS Mogalekar, author of 'Fishes from Tamiraparani river system', says the number of fishes observed in the Thamirabarani river system is greater than that given in the earlier reports from Tamil Nadu. However, the researcher attributes this to lack of research on fish diversity.
Speaking to TNIE, Nilanjan Mukherjee, a research consultant at ATREE, said that Thamirabarani is home to numerous endemic fish species. However, due to non-availability of literature on the fish diversity in the river, an effective comparison is not possible, he added.
"In the 1970s, Common carp, Tilapia and Guppies or Gambusia were the invasive species recorded in Thamirabarani. Now, the situation has changed with the invasion of African sharptooth catfish (Clarias gariepinus), Pleco tank cleaner catfish (Pterygoplichthys species) and Tilapia (Oreochromis species), which pose threats including loss of biodiversity, health hazards and economic damage. The dams prevent migration of fishes and it could affect the population of certain fish species like Mahseer and Labeeo, which swim upstream to breed during its reproduction," he said.
Mukherjee also called for a detailed study on the diversity of fishes in rivers terming it essential for any conservation strategies. Meanwhile, another researcher Mathivanan opined that the state and central governments must encourage researchers to do more exploration on fish diversity.