OK, if your name is Wayne Leibel or Juan Miguel Artigas do not read this! I do not want to see a wanted poster with my picture on it in the next Buntbarsche Bulletin. After many experiments I have solved the Chaca chaca feeding problem.
My Chaca are are happily stuffed on the fry of Convict cichlids ("Cichlasoma" nigrofasciatum), "Cichlasoma" nicaraguense, and Thorichthys elioti. The little cichlid fry dive straight to the bottom of the tank and start sifting through the sand and peat for food. As soon as they are too near the mouth of a Chaca...Gulp! Now, how am I going to find a constant source of cichlid fry without devoting a tank to cichlids?
I had tried feeding various Cyprinids (danios, goldfish, and rosy red minnows) without much luck. The problem was that Cyprinids, for the most part, dwell at the water's surface and thus never went near the Chaca. Chaca are often referred to as "anglers" so it would make sense that they would use their barbels to imitate a small worm and lure the Cyprinids to them. In over a year of maintaining a tank of Chaca chaca I never saw them "angle" in an attempt to lure prey.
Watching the Chaca feed has convinced me even more that they are not anglers. They lay buried in the sand with only their eyes showing (like a crocodile) and just wait. They are so expertly camouflaged that their prey will swim right to their mouths. When the prey is detected the mouth opens and creates a vacuum as water is pushed out through the gills. This current sucks in the prey so fast that I was amazed! The other cichlids swimming an inch away (2.5 cm) from their departed friend never even noticed their buddy was gone. It all happened so quickly that they never knew what happened and proceeded to get closer to the Chaca. Then "Woof!" and another cichlid was gone. Amazing!
It actually makes a lot of sense that they would feed this way. We all know that Chaca can move like a torpedo by expelling water from their gills with enough pressure to propel the Chaca along. This same pressure system is put to use as a vacuum when feeding. It also makes sense for an ambush predator to do this because they do not have to give up their position to their prey by lunging. After eating two or three fish this way, the Chaca swim to a different section of the tank and bury themselves again. My guess is that they are acting like a sniper. Take a couple of shots and then move so your prey can never really figure out what is going on.
While I am quite convinced Chaca hunts by ambush and not angling, I still can not prove it. There is always the argument that they behave differently in captivity. We, of course, can not disprove this since no one has observed these fish feeding in the wild. The best answer would come from gut content analysis. If the majority of their diet consists of bottom dwellers (catfishes, loaches, and eels; all of which are common in the natural habitat) and not mid and upper water fishes, then it would lend evidence to the thesis that Chaca feeds by ambush and not angling.
Whatever the answer is they are still great fish. Anyone have a couple of hundred extra cichlids laying around?
There is further information on this species on the Cat-eLog page.
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