|
The Ambush Predator-Nimochromis linni
During one of my trips to Lake Malawi in 1990 I had the opportunity to study one of my favourite cichlids the Nimbochromis linni and its natural hunting methods. Before the trip I had kept several N. linni in my tanks and even had it spawning on one occasion. The spawn resulted in some 80 hungry little "Pangolins" (that's what my colleague Janne Hägglund used to call them). After this experience of course it was something extra to be able to meet this "old friend" in its natural habitat. Facts First of all some facts about the species. Nimbochromis linni is a quite common cichlid all over Lake Malawi. There are no color variants known today. Breeding males get a green-blue metallic shine all over their bodies with a bright blue spot on their gill covers, but even a fully colored spawning male never looses the pattern on its body. There is an orange or red line running along the tip of the dorsal fin. This color is also present on the anal fin of a spawning male. How red this line gets depends on the amount of color enhancing food the cichlid is given. It is a very large "hap" reaching a size of about 12 inches as an adult. Because of this it needs a large tank, preferably larger than 130 US gallons. Despite its size it is not very aggressive in an aquarium not even towards its own kind. It works well together with other peaceful "Haps" or Aulonocaras. The females are usually very good at taking care of their young. My female kept taking her fry back into her mouth as the lights went out for at least two weeks after spitting them out for the first time. I even kept her together with the fry for some time after that and as far as I know she did not eat a single one. The fry on the other hand eat a lot and grow very fast if cared for in the right way. The males get their full coloration at about 4-5 inches at least this has happened in my case.
My story Getting back to my story, it was the very last day of my visit to Cape MacLear and Lars Andersson and I rented a "dough-out" (a hollowed-out tree trunk) for a few kwacha and paddled out to Thumbi-island. We needed one last dive before returning to Sweden. By then we were quite used to paddle the "dough-out" so it didn't take long before we passed what is called "the aquarium" and pulled our dough-out up against the cliffs at Mitande Rocks at the south-east point of Thumbi-island. We strapped on our masks and fins and started our hunt (for photographic motives). Lars wanted to find a Geophyrochromis mento before leaving the lake and I was looking for the Nimbocromis linni. The "Aquarium" Slightly left of the two large rocks we had in front of us there was
a formation that looked like The stones on the bottom were covered with algae and mbunas of different kinds were peacefully grazing on it. The majority of the species I could see were of dark blue or brown coloration. A Nibochromis linni After moving around this natural aquarium for a while I suddenly stood face to face with a Nimochromis linni. At first I didn't recognise it as it stood completely still with its snout wrapped around a small rock and its belly tucked to the substrate. This species is also very difficult to see with its brown camouflaged body against this reddish-brown algae covered rock, but as I came close it got scared and swam of to a new hunting position. Due to the fact that the water was only about 3 feet deep where it was hunting and the sunlight was very strong I managed to get a few very satisfactory pictures. Maybe these pictures are the best I managed to take during this trip; I'm no Ad Konings you know. For those interested in photography maybe I should mention that I was using a Motomarine II camera. Probably there were lots of fry hiding between the rocks and that was what the linni was after.
Ambush predator Its hunting technique is rather simple. The fish positions it self in a habitat with plenty of medium sized rocks pushing its frontal body against a chosen rock. The long snout is placed in a strategic position in a gap. In this position it stays perfectly still waiting for fry to come out of their hidings. When this happens the N. linni reaches out its long snout that opens up downwards and vacuums up it's pray. It did not seem to matter which way it turned its belly, sometimes it would lay flat on its side and on at least one occasion I saw it positioning underneath a rock with its belly up. It was all the time moving very close to the substrate, a bit like a Julidochromis from Lake Tanganyika. During the 10 minutes that I was observing the fish it did not stay in one place for more than about 15 seconds. It was moving quickly from one rock formation to the next all the time placing its snout in little holes. I am pretty sure that this rapid movement was because I was following it with my camera. According to what I have read it usually lies waiting for it's pray for several minutes. This also corresponds to my studies of it in the aquarium where I have seen it lay still as in a trance, belly against a rock and snout in a plant for a very long time. I followed the linni for about 10-15 minutes before I started freezing in the 74 degree water. When I got back into the water after warming up in the sun for a few minutes I was unable to relocate the fish. I don't believe "my" linni was able to catch any fry during the time I was following it. When Lars and I felt we had seen enough for the day we slowly paddled the dough-out home. I was a bit sad leaving, maybe it was the last time one had the opportunity to scuba dive in an aquarium, then again, who knows....
|
|
Roger has promised to send us some of the photos he took in "The Aquarium" that day and as soon as we get them they will be published together with the article. Roger häggström is the former editor of the Swedish cichlid
assosiation magazine "Ciklidbladet". |
