THOOTHUKUDI: Nearly 36 different fish species and 1,197 individual fishes were found after the Thamirabarani Fish Count (TFC), an ichthyological survey of fish in the Thamirabarani.
Ashoka Trust for Research in Ecology and the Environment (ATREE)'s Agasthyamalai Community Conservation Centre (ACCC) conducted the fish count, in collaboration with the Sri Paramakalyani Centre for Environmental Sciences, and the Department of Zoology of Sadakathullah Appa College, Palayamkottai, on March 23.
It is ATREE's first annual survey, aimed at documenting native fish species, identifying invasive species and outlaying effective conservation strategies.
The TFC follows the conventional method of identification and counting with three kinds of nets, including cast nets, drag nets, and scoop nets. Nearly seven groups of volunteers, comprising experts, fishermen and students, conducted surveys across seven locations — Papanasam, Kallidaikurichi, Thirupudaimaruthur, Gopalasamudram, Seevalaperi, Karungulam, and Srivaikuntam along the Thamirabarani. The volunteers netted the fish at nearly 10 different spots in every site.
The volunteers managed to identify a total of 36 fish species and approximately 1,197 individual fishes during the survey, which lasted for a day. Fishing sites at Kallidaikuruchi and Srivaikuntam saw the highest number of species — 16 and 17 respectively. Srivaikuntam, where the last anaicut is located, also recorded the highest number of individual fish count — 415.
Among the 36 species, 31 were identified as native species, two introduced and three invasive species. The volunteers had sighted endemic species such as the Thamirabarani Barb, Mahseer, Half Beak fish and Torrent Catfish, as well as the rare Smooth-coated Otters at Papanasam.
TFC coordinator M Mathivanan told TNIE that the survey is an attempt to study the diversity of fish species in the Thamirabarani and document them. It is pertinent to note that nearly 125 species were documented before.
Annual surveys help ascertain the changing biological factors of the water body, threat to native fish populations, exacerbating biodiversity loss, health risks and economic damages, he said.
Professor Muralidharan of Sri Paramakalyani Centre for Environmental Sciences, also the joint coordinator of TFC, said that the survey focused on freshwater species, and the estuarine fish survey will be conducted separately.
The Torrent Catfish, which inhabit the undercuts of bedrocks in the hilly upstream, were sighted in the plains of Papanasam. "The sighting of Torrent Catfish at Papanasam may be due to the December 2023 floods," Muralidharan said.
Another researcher, Surya, said that invasive species have been pervasive in the Thamirabarani. Invasive species such as the Pleco Tank Cleaner and African Catfish were found in significant numbers between Thirupudaimaruthur and Srivaikuntam, he said.