Sexing Melanochromis johanni Cichlid Fish

How can I tell the difference between male and female Melanochromis johanni cichlids?

Q. I’ve recently purchased two Melanochromis johanni cichlid fish from a newly opened local pet store so I could breed them. I was assured by the salesperson that they were  male and female Melanochromis johanni cichlid fish. When I took them home, both fish were orange, with an identical yellow spot in the anal fin, although one individual had a black line running through the dorsal and anal fins.

This cichlid fish, which I think is a male, has developed a pattern of smokey colored stripes and bars and a couple of blue stripes on its forehead. He chases the other fish constantly and behaves so aggressively that I have had to catch him and put him in a breeder net. When I do this, the other cichlid fish uses all the male’s favorite hiding places, develops a very similar dark coloration and tries to attack the male in the net. Is it normal for a female M. johanni to act in this way?

Although the shop guaranteed that the cichlid fish were a pair, is it possible that I have a dominant and a non-dominant male? I would like to order a female, but first I’d like to be sure of what I have.

A. You have, I am afraid, hit the nail on the head. A female Melanochromis johanni cichlid fish retains the deep orange-yellow juvenile coloration of this species into adulthood. While females of some populations may show indistinct cinnamon-brown longitudinal stripes as they age, they never develop either the sort of duskiness you report or a distinct pattern of metallic blue frontal stripes.

The behavior you report is also a dead giveaway of this cichlid fish’s sex. Apart from a few algae-farming species of cichlid fish, like Pseudotropheus elongatus, in which both sexes defend a permanent feeding territory, only male mbuna display territorial behavior and challenge one another in the manner you have described.

In retrospect, it does not surprise me that the pet store salesperson sold you two male cichlid fish as a pair. In a crowded situation, it is not unusual for males of many Melanochromis species to retain most elements of their species juvenile color pattern well after the process of sexual maturation has begun. Looking as little like a male as possible is an effective means of avoiding the attentions of a dominant male.

Unfortunately for aquarists, this defense mechanism does not make the task of selecting a future cichlid fish breeding group from an aquarium of young fish any easier! When you go to select your female, make certain that that you choose only those individuals that show an obvious uniform yellow-orange coloration on both the body and fins, and no trace of a yellow spot in the anal fin.

While subordinate males may be able to effectively suppress the patterns of black body pigment typical of their sex, the yellow pseudo-ocellus present in the anal fin of the generality of mbuna is one color pattern element they cannot turn off in response to social pressure. Fish that display a clearly defined yellow spot in the anal fin are most probably males — those that lack it are invariably females.

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Fish · Freshwater Fish