IN SEARCH OF KILLIFISH
de Silva Wijeyeratne, G. (2009). In search of Killifish. Living. March – April 2009. Pages 32-33. Volume 4, Issue 4. ISSN 1800-0746.
Finding an aquatic predator in the Talangama Wetland.
I was stalking a predator, to photograph it. Not the usual Big Spotted One I do in Yala. This was one was very small, just a few centimeters in length. To complicate matters it lived under water. So I would first have to catch it before I could photograph it. I stealthily prowled a ditch connecting to a small pond in a private nature reserve in Talangama where I knew I could find a shoal of them. Holding a small net in my hand I hunched over the ditch and slowly immersed the net to scoop out a killifish.
Killifish had intrigued me when I first read about them. I had read how ephemeral pools in the interior of forests become filled with fish with the rains. These fish would have no way of reaching these pools other than when heavy flooding took place. So how did the fish survive through one dry season through to the next wet season? Well, perhaps they did not, but the next generation did. A group of adult killifish may colonise an ephemeral pool in a flooded forest. This could be simply a shallow scrape on the ground. They mate and lay eggs amongst tangled vegetation. The forest dries out as the rains recede. The pool of water will gradually dry out and the adults may perish. The eggs however survive the dry season and with the next onset of rains, a new generation hatches out and the pool is alive with killifish again.
In Talangama I had observed this circle of life. On higher ground where it did not flood each year, killifish were to be seen. They probably were a generation which had not seen their parent generation. The killifish do have one more trick up their sleeve. They are not necessarily doomed to die in a drying out ephemeral pool. The adults can leap out of the water and fling themselves around on dry land to hop across to another body of water. They may even do this to escape from a predator which has entered their pool of water. They seem to be able to sense the presence of nearby bodies of water and leave one body of water for another.
Although I had read about this much earlier, it had taken me several years to take a proper look at the killifish. The vertebrate animals have a special place in the minds of field naturalists. These are the birds, mammals, reptiles, amphibians and fish. They are the most evolved and intelligent of the various animals. Of the vertebrates, the fish have a very small but dedicated following of naturalists, but seemed to have escaped the attention of many ‘wildlifers’. I suspect this is because to view them properly they need to be seen laterally, which would require viewing through a fish tank.
The killifishes of Talnagama and many other semi-urban environments look quite plain when viewed from above. They are called ‘handayas’ in Sinhala, a reference to the white spot on their head, which is similar to a crescent moon. Viewed laterally they are beautiful.
I transferred one of the ‘handayas’ I had caught into a fish tank and I took it inside a bird hide to photograph it. I assumed it was the commonest of the three species of killifishes found in Sri Lanka, the Dwarf Killifish also known as the Dwarf Panchax. Two other species are found in Sri Lanka, the Day’s Killifish confined to the Kelani River basin and adjoining coastal areas and Werner’s Killifish found in the Kalu and Nilwala River basins. Using Rohan Perthiyagoda’s excellent book, ‘Freshwater Fishes of Sri Lanka’ I confirmed that I had photographed the Dwarf Killifish found throughout the lowlands. From the book I also gathered that what I had was a male, judging by the red edging to the dorsal fin. My usual view, a top view of the killifish had been of a nondescript, olive green fish with a white spot on the head. Barely worth a second look. Viewed side on, it was transformed to a beautiful, elegant animal with an oval tail and with elongated dorsal and pelvic fins decorated in yellow and red.
Sri Lanka’s freshwater fishes are neglected by the general wildlife enthusiasts. This is a pity because our native freshwater stream fish are very special. Just over half of them are endemic. Rohan Pethiyagida and other researchers have added several new species of fish by looking more closely at what we have. Several more fishes are yet to be described. Madura Silva of the Wildlife Conservation Society told me in December 2008 that members of the society were working with Rohan Pethiagioda on the description of even more species new to science. The society’s base at the wonderful Hiyare Reservoir Rainforest is one of my favourite places to look at fish. In fact much to my shame, I have to admit that before I looked closely at the common Dwarf Killifish, I first had to succumb to photographing the rarer and more beautiful Werner’s Killifish at Hiyare.