Saturday, July 23, 2011

Some special freshwater fishes of Sri Lanka

My interest on fish started at a very young age. Initially it was a few Guppies borrowed from a friend in school and which I kept in a huge toffee bottle. But then, to a bigger fish tank and another. Joining YZA was the climax of this. There, I was able to scientifically learn & study about all the freshwater fish species in Sri Lanka.

In this aspect too, our country is a blessed region, since we are very rich and diverse in fauna & flora. Sri Lanka is currently home to 80 odd indigenous freshwater fish species. (I'm a bit confused on the exact figure due to a few rapid changes and additions that have recently taken place in this sphere). Most people are startled to hear this fact and are also utterly unaware of the array of species our country possesses. Hence, on the positive, awareness through whichever means would benefit the conservation of our fauna & flora for generations to come. On these lines, I thought of sharing some acquired knowledge of freshwater fishes of Sri Lanka with you. And as it's difficult to provide information on each and every fish, I've chosen a few special species - although there are more - for this blog post.

1. Hora dandiya - Rasboroides atukorali - හොර දණ්ඩියා

I'll start from the two extremes. Previously known as Horadandia atukorali, this little fellow is the smallest freshwater fish in Sri Lanka growing to an average length of 2 cm or less. It belongs to the Cyprinidae family which accounts to the most number of species in the country. This fish has no lateral line and is transparent in colour with a light green hue. They often live in large schools close to the surface while feeding on planktons. It is a somewhat weak fish compared to other Cyprinids. Has been reported from the wet zone (locations such as Diyawanna Oya, Attidiya, Matugama) and Yala in the dry zone. Not an endemic species.

2. Shark catfish - Wallago attu - වලයා

A Walaya caught at Kitulgala - from Rohan Pethiyagoda's 'Freshwater fishes of Sri Lanka'

From the smallest now it's to the biggest. The Wallago is the largest freshwater fish in the country which measures to a maximum length of 5 feet, although individuals of this magnitude are very rare. Since its rarity in recent times, the Wildlife Conservation Society of Galle had once requested to report any sightings of the fish as part of a survey carried out by them. This species belongs to the Siluridae family which boasts of many large individuals.

The Shark catfish is blackish brown in colour and white underneath. It has two pairs of barbels out of which the maxillary is very long. The mouth which extends beyond the eye, suits its nature of being a voracious carnivore. Mostly active at night, its diet includes small fish, reptiles, birds and even mammals! This is a solitary creature that lives in deep pits in large rivers or tanks. It has been mainly reported from areas such as Kitulgala, Mahaweli River and tanks in the dry zone. Harmful means of fishing such as dynamiting is believed to have contributed towards the diminished numbers of this species and resulted in being extinct from some of the previously inhabited locations. It is not endemic to Sri Lanka and is also recorded from India.

Now I move onto a couple of fishes with unusual habits.

3. Archer fish - Toxotes chatareus - දුමිත්තා

     An Archerfish shoots at a target

Ever heard of a fish that spits? Well, this one certainly can. In fact, that's a way it hunts for food. And as its name implies this fish is a skilled shooter, which channels a jet of water towards a target over the surface thereby hitting the pray and causing it to fall. The younger ones are not very accurate, but they eventually develop and learn to deal with the angles concerning the refraction from air to water. This species is an average sized fish and shows a distribution from India to Northern Australia. It is found in both fresh and brackish waters and often in lagoons too.

4. Upside down sleeper - Butis butis - නිදිමතයා

     Laying upside down

Although called a 'sleeper', it's just a position that this species is sometimes found lazing around, not that they actually sleep (even its Sinhala name presents the same meaning). They are often found lying in one place on a surface. Due to this weird behaviour, it's sometimes even referred to as 'crazy fish'. This species belongs to the Eleotridae family which has another individual - Eleotris fusca - in Sri Lanka. It is carnivorous and feeds on smaller fish or crustaceans. Lives in fresh and brackish water while commonly found in lagoons, estuaries, swamps and lower reaches of freshwater streams.

The last two I've chosen are a bit unusual in appearance.

5. Freshwater garfish - Xenentodon cancila - යොන්නා

The Freshwater garfish is a 'needle fish' - because of its shape - and belongs to the Belonidae family. It grows to a maximum length of one foot although most reported are about 8 inches. Has big eyes and long jaws, and teeth of the bottom jaw protrude out while the upper ones don't. Length of its head is almost half the total body length. A dark band with a margin runs along the side of its body. They prefer to stay in one place, close to the surface in wide streams or large rivers. It's not the best-known swimmer and usually are found in packs of 7 or more. As a carnivorous individual, it feeds mostly on small fish & frogs, tadpoles or crustaceans and hunts mostly at night. The Garfish has been reported from areas such as Waga and Kithulgala while I once observed it in a tributary of the Magal Ganga at Deraniyagala. It's at times mistaken for the 'Halfbeak' known as මොරැල්ලා in Sinhala.

6. Ocellated pipefish - Microphis ocellatus - නැට්ටා

This fish belongs to the family Syngnathidae which includes Sea Horses too; the major difference being that sea horses hang about vertically (yes, they are fish. Not horses, or for that matter mammals!). These fish have a series of bony rings that encloses their body and have no scales. They feed by sucking into a tubular snout. Males have a brood pouch in which the eggs are laid, fertilized and incubated. It grows to a maximum 6 - 7 inches in length and is a VERY slow swimmer. It's also a very rare species and has been recorded only from a few locations in the wet zone. (e.g.: Avissawella, Agalawatta). Mainly occupies slow flowing habitats although may exist in fast flowing locales as well.