Fighting the aliens at Periyar Tiger Reserve

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Periyar Tiger Reserve (PTR) is not just a safe haven for the tigers, but for some aliens too, in the ecological sense. African cat fish (Clarias gariepinus), one of the most dangerous invasive alien species, is lurking in the Periyar Lake, raising serious threat to the rare fishes found only in Periyar, say researchers. To bring a twist to the story, PTR is going to have the first of its kind action against exotic fish species in Western Ghats as a group of researchers and activists are aiming to manually remove African cat fish from Periyar with public participation.

African Cat Fish (Clarias gariepinus)
Image Credit : W.A. Djatmiko (Wikimedia Commons)

According to Conservation Research Group- a research and activist platform based in St Albert’s College in Cochin- which organises the exotic fish removal campaign at Periyar Tiger Reserve, the endemic fishes found in the Periyar Lake are severely threatened by the biological invaders like African Cat fish, which inspired them to organise such a crusade against the alien fish species of PTR.  “Eight endemic fishes in Periyar Lake are fighting for survival as their only remaining habitats are threatened by several stressors of which biological invasion is the most significant one.”, says an official statement from the group.

Importance of Fish fauna in Periyar Lake

An on-going Rufford Foundation supported project to study the impact of alien species in Periyar Lake points out that the fish fauna in the Lake are very unique and valuable. “It (The Lake) holds the only remaining population of six globally threatened endemic fish species viz. Crossocheilus periyarensis, Garra periyarensis, Hypselobarbus periyarensis, Lepido pygopsistypus, Nemacheilus menoni and N. Periyarensis”, it says. According to an IUCN report on the Status and distribution of freshwater biodiversity in the western Ghats, Lepido pygopsistypus  is the only member of its subfamily of snow trout fishes to be reported from south of Himalayas.

According to the researchers, there are four exotic fish species found in Periyar Lake which comes under the reserve among which African Cat fish is the most dangerous one when it comes to threat to native species. Cyprinus carpio, Oreochromis mossambicus and Poecilia reticulate are the other exotic fish species found in the Periyar Lake Stream System (PLSS). Recent studies have indicated that the population of these exotic fish species are showing an increase which means that the threat to native species is growing. “C. carpio and O. mossambicus now dominate the fishery of Periyar Lake and are known to compete with endangered species such as L. typus and Crossocheilusperiyarensis”, says a recent study report issued by IUCN.

The invasive species have swept away many native fish species found in the lake earlier. During the last 50 years, at least 16 fish species earlier found in the lake has disappeared, say researchers.

Fighting the Aliens

African Cat fish in Periyar Lake and other freshwater ecosystem in Western Ghats is the usual story of an introduced species turning viral threat to native species. African Cat Fish was once widely used as a farm fish in Kerala and elsewhere for its rapid growth. It soon became very popular with its ability to survive in a range of water qualities and to devour anything from slaughter house waste to standard fish foods. However, the alarm started ringing when some of them have escaped through the natural water channels from fish farms during monsoon and reached the fresh water systems in Western Ghats. 

Exotic Fish removal campign at Periyar Tiger Reserve

The IUCN report has suggested that “the biggest future challenge to fish conservation in PLSS will be the management and control of C. gariepinus, whose opportunistic strategy and ability to establish large and persistent populations makes it an imminent threat.”

To fight the alien menace, a workshop conducted by researchers and forest officials at PTR in December 2012 has decided to take pro-active action against the invasive species. Field work has revealed high population of African cat fish in the canal draining into the Lake. The authorities and researchers are planning to net out the exotic fishes from the canal and manually remove the exotic fishes from the Lake. The organisers of the event were not available for immediate comment. However, according to an official invitation, the programme is scheduled on April 29^th and 30^th of this month.