AAGB

Ctenopoma intermedium from Okavango

by Dr. Jim Cambray, Albany Museum, Grahamstown

I collected the Ctenopoma intermediumwhen I was in the Pan handle area of the Okavango swamps in Botswana. The river was flowing quite strongly but I only wanted to go to the open flooded margins, away from the densely, papyrus-vegetated main channel. I hired a dug-out canoe and two young boys of about 10 years of age took me to what I thought would be Ctenopomacountry. We made our way through the thick papyrus, following hippo paths, very useful for canoes IF there are no hippos. We were also warned about crocodiles in the area, so after carefully scanning an area, I set foot in what turned out to be an exciting and successful collecting trip. I had a small scoop net and proceeded to walk around a large, shallow grassy area looking for depressions (probably caused by hippos) where I thought C. intermedium would occur.

After about 30 minutes of scooping I came up with my first male of a few centimetres in length and almost as darkly coloured as in the photograph. The area was thickly overgrown with grass and the water was shallow, less than 15 cm deep. No other fish were collected with the Ctenopoma. After another 10 minutes I collected several smaller juveniles and then thought that I should have another look around for the crocodiles. I later had a look for the small bubble nests the Ctenopoma males construct but none were observed. Water values in the Seronga area were: conductivity 12.7 mS/m ; pH 7.6; water temp. when I collected fish, around 25C. After several hours my 'taxi' was waiting and I returned with my small catch. It was interesting that when I went to pay for my ride the two young fellows did not want money, they wanted very small fishing hooks to catch young cichlids. I took them up to the local bush `shop' but as to be expected they were out of small hooks. They reluctantly had to take my money and left me feeling guilty that I did not have the right currency for the panhandle taxis.

A few days later I was in a small aircraft flying back to Grahamstown with the fish in a plastic bag on my lap. They all made it and within the month a male had made a bubble nest in a thickly vegetated tank at 25-27C; Conductivity: 150 muS/cm; pH 7. Unfortunately, he mated and killed both his females overnight without me being able to observe the mating or remove the females. This particular male is the one featured in the slides. He aggressively defended his nest, but using unfair tactics I removed his nest with the eggs as I wanted to observe and record their development. The eggs were 0.78 mm, almost colourless with a large central oil globule of 0.49mm. Many of the nest bubbles I measured were also very close to the diameter of the eggs. He later went on to develop the long dorsal and anal finage, which other males did not do, and a lovely dark breeding coloration with a bluish sheen.

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