A random fish count conducted at seven places along the Tamirabharani watercourse has revealed that the perennial river has 36 fish species and rare smooth-coated Otters in Papanasam area.
The Tamirabharani River, the southernmost major east-flowing river in peninsular India, stands as Tamil Nadu’s sole perennial river. Originating from the scenic and salubrious Agasthyamalai Hills in the Western Ghats, it traverses approximately 130 Km and nourishes over 88,000 acres of land before entering the Gulf of Mannar. The river basin boasts a highly diverse fish fauna, with a 2019 study documenting 125 species, including six endangered and four threatened species. These fish contribute significantly to Tamil Nadu’s freshwater fish diversity with seven endemic species exclusive to this river basin.
ATREE’s Agasthyamalai Community Conservation Centre (ACCC), as part of its ‘Citizen Science’ programmes, conducted the Tamirabharani Fish Count in collaboration with Sri Paramakalyani Centre for Environmental Sciences, a satellite centre of Manonmanium Sundaranar University, Tirunelveli and the Department of Zoology, Sadakathullah Appa College, Palayamkottai in the last week of March.
This effort aims to document native fish species, identify invasive species and formulate effective conservation strategies.
The survey started with a workshop in Kallidaikuruchi on March 22 bringing together students, local volunteers and members of fisher community to learn the sampling and counting protocols. Seven teams comprising experts, fishermen, and students conducted surveys the next day in as many locations along the Tamirabharani riverrcourse at Papanasam, Kallidaikurichi, Thirupudaimaruthur, Gopalasamudram, Seevalaperi, Karungulam and Srivaikundam.
Cast nets (10 mm) with 10-feet diameter were flung into the river at different micro habitats such as sandy, rocky, weedy, swamp and bathing ghat areas of the river to catch the fish which were counted before being kept in bucket-full water to ascertain the ‘fish density’ in these spots. The fish weighed between 20 grams to 500 grams. They were released back into the river when the survey is completed in a particular micro habitat.
“The surveys revealed 36 fish species and approximately 1,197 individual fishes. Kallidaikurichi and Srivaikundam recorded the highest number of species with 16 and 17, respectively. Srivaikundam also recorded the highest number of individual fish with 415 fish counted and safely released,” said M. Mathivanan of ATREE.
Other locations documented between 13-15 species each. Out of 36 species, 31 are native species, two are introduced and three are invasive species. Notable sightings included the endemic Tamirabharani Barb, Mahseer, Half Beak fish and Torrent Catfish. The presence of rare Smooth-coated Otters at Papanasam underscored the river’s vitality.
“Despite these findings, the Tamirabharani river faces significant threats from unchecked pollution, invasive species proliferation and dam mismanagement. Invasive species pose a severe threat to native fish populations, exacerbating biodiversity loss, health risks and economic damages. Unethical fishing practices such as dynamite and bleaching powder usage further aggravate the challenges. It is imperative for the government to take decisive action against invasive species and unethical fishing practices to safeguard the river’s ecological integrity and ensure the well-being of its inhabitants,” said Prof. Muralidharan of Sri Paramakalyani Centre for Environmental Sciences.
