The Sri Lanka Spiny Eel, a freshwater fish that was common in the early ’80s is probably now extinct. This was revealed by Prof.Devake Weerakoon delivering a talk on the Red List, at an event organised by the Open University’s Botany society. Sri Lanka is home to six species of eel known as ‘aandha’ in Sinhala, given its slippery, slimy nature. The threatened species, the Spiny eel, is scientifically known as Macrognathus pentophthalmos.
The Sri Lanka Spiny Eel was categorised as a common freshwater fish endemic to Sri Lanka in studies done in 1932 and 1980. But an islandwide freshwater fish survey conducted by researcher Rohan Pethiyagoda in 1991 failed to record even a single specimen of this eel. This prompted the Wildlife Heritage Trust in 1992 to print an illustrated ‘wanted’ poster that was displayed at leading ornamental fish export companies and inland fisheries centres islandwide offering a reward to anyone who spotted even a single specimen of the Sri Lanka Spiny Eel and another fish that had suffered a similar fate, Labeo Lankae. There were no positive results regarding the sighting of the Spiny Eel and in 2008 Dr. Pethiyagoda published a scientific paper that analysed the fate of this fresh water species.
The Wildlife Conservation Society of Galle (WCSG) is currently conducting an islandwide fresh water fish survey. But that too has so far failed to collect any data on the Sri Lanka Spiny Eel, Nadika Hapuarachchie of the society said. The Sri Lanka Spiny Eel was categorised as ‘Critically Endangered’ in 1994 and based on the results of latest surveys, the National Red list of Sri Lanka published in December last year reclassified the species as “Possibly Extinct”.
The Sri Lanka Spiny Eel has a slender body like other eels and has got its name for its sturdy fin spine. Another member of this family, the Marbled Spiny Eel (Mastacembelus armatus) is still a commonly found fish. But environmentalists point out that even the population of this common species can dwindle suddenly and regular monitoring is needed to evaluate its threatened levels.
Sri Lanka is known for its rich and diverse freshwater fish comprising 91 species of which 50 are endemic. Sampath Goonatilake of the International Union for Conservation of Nature (IUCN) who has written a chapter on freshwater fish in the National Redlist says that arguably this is the most vulnerable taxonomic group as most of the threatened or endemic freshwater species are found in streams that lie outside the Protected Area Network of Sri Lanka. These habitats are vulnerable to various threats such as forest clearance, gem mining, expanding agriculture, large and small scale hydro projects, exposure to chemical pollutants including agrochemicals and sedimentation due to soil erosion, he said.
Meanwhile, according to the global Redlist 2009, Sri Lanka is placed 14th in terms of percentage numbers of threatened species. This is not good news given that Sri Lanka is a global biodiversity hot spot.
Invasive species big threat
Invasive fish such as the Thilapila that have been introduced are behind the decline of Sri Lanka’s native freshwater fish. The knife fish (Thilapila) brought to Sri Lanka for aquarium trade has been reportedly introduced in water holes and streams in many areas. A giant knife fish was caught last week at a water hole in Boralasgamuwa. Praki Bandara who captured this image says the fish weighed more than seven kilograms.
The Knife Fish is a carnivore’s species that feeds on other smaller fish and their eggs. They are native to South East Asia. The knife fish is a popular aquarium fish because of its rapid growth. When they outgrow fish tanks some people release them to natural waterways, not giving heed to its detrimental effects on the population of other fish. There are instances where knife fish are washed away into natural water holes especially when ground fish tanks overflow due to flooding. Environmentalists urge the public not to release this species of invasive fish into natural waterways as they are harmful to native fish.
Eel – the slippery freshwater fish
It’s a slippery, slimy creature, and doesn’t fit into the image of what one perceives as freshwater fish. But the eel is a regular fish – that doesn’t look like one. It has a serpentlike head and a snakelike body. The Eel’s body is elongated and flexible. When it swims, it moves in a series of waves. These waves cause each segment of the eel’s body to oscillate in a figure-of-eight. This movement causes the eel to be propelled forward in the water.
According to studies there are about 800 eel species that inhabit freshwater and marine habitats. A majority of eel species are nocturnal. Globally there has been a drastic decline in the numbers of eel species. A research in UK revealed that the European Eel population in the River Thames had fallen by 98% in just five years. This decline could be due to changes in oceanic currents due to climate change, man-made structures such as dams and the presence of certain diseases and parasites, the study revealed.