Survey by forest dept reveals Catfish posing threat to native species in Periyar Tiger Reserve

The survey identified 56 fish species, making it the highest count ever from any study conducted in the PTR since 1940.
Cat fish
Cat fishPhoto | Express

KOCHI: The first composite aquatic faunal and odonate survey conducted by the forest department in the Periyar Tiger Reserve (PTR) from May 16 to 19 reveals a decline in population of native species due to the increase in population of exotic species like catfish.

The survey identified 56 fish species which makes it the highest count ever from any study conducted in the PTR since 1940. The study revealed the presence of seven new species of fish from the various tributaries inside the PTR. The PTR will have to conduct molecular studies to confirm whether these species are new or the subspecies of existing fish species.

Various water bodies in the PTR harbours 30% of all fish species found in Kerala. Among them, nine fish species are restricted to the boundaries of the reserve — all of which but one, could be recorded during the current survey. Four exotic fish species, including Clarias gariepinus (African Catfish), Cyprinus carpio (Common Carp), Oreochromis mossambicus (Mozambique Tilapia), and Oreochromis niloticus (Nile Tilapia) were recorded in the survey.

“Over the years we have observed a decline in cormorants and darters in our lake. This can be attributed to the decrease in population of native fishes and increase in the population of catfish. In 1986, catfish from a nearby fish farm had entered the lake during floods. We had found more exotic species in the lake after the 2018 floods. The survey will help understand the population of native fish,” said Periyar East Assistant Field Director P J Shuhaib.

Lepidopygopsis typus
Lepidopygopsis typus

The survey to study the abundance of odonates like damselflies and dragonflies revealed the presence of 120 species as against the previous record of 116 species. This is the highest number of odonates ever recorded in any protected area in Kerala, and comprises 63% of the odonate diversity of Kerala and around 55% of Western Ghats.

“The odonates are clear indicators of air and water quality. We have observed the presence of odonates in all camp sheds, especially the Meghamalai area where the tea estates are using pesticides. There are odonates that are found around freshwater lakes and contaminated water bodies. The survey primarily aimed at identifying the species. We will conduct a post-monsoon assessment to study the variations,” said Shuhaib.

After identifying the threat posed by exotic species to native species, the forest department had initiated steps to eradicate exotic species. Around 2,780 catfishes were eradicated during the past two years. The department is utilising the service of local fishermen to control the population of exotic fishes. Another exotic species is Glossogobius which was identified in 1974.

“The presence of the micro-endemic fish species signifies the success of the PTR’s management interventions in controlling invasive species. This demonstrates a healthy aquatic ecosystem where native species can thrive. Further studies are also planned to describe the newly encountered species,” said PTR field director P P Pramod.

Around 75 experts from south India and members of fishermen eco-development committee of Periyar Tiger Reserve participated in the survey. Periyar East Division deputy director Patil Suyog Subhash Rao coordinated the survey which was led by nature education officer Sethu Parvathy, IUCN dragonfly specialist group member S Kalesh, South Asia Chair of the IUCN Freshwater Fish Specialist Group Rajeev Raghavan and other experts.

Surprise threat

In 1986, catfish from a nearby fish farm had entered the lake during floods. More exotic species were found after the 2018 floods. Identifying the threat, the forest dept initiated steps to eradicate exotic species. Around 2,780 catfishes were eradicated in the past 2 years

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