Are All Cardinalfish Mouth Brooders?

What is Mouthbrooding?

• Mouthbrooding is a level of parent care uncommon in the world of fish. In most fish species, the eggs are fertilized and deposited -- often on a solid surface -- then left to develop and hatch on their own. With mouthbrooding, fewer eggs are needed because their likelihood of survival is much higher than for eggs left unattended. Also called oral incubation and buccal incubation, mouthbrooding can be carried out by the male or the female, depending on the species. In very rare cases the male and female parent each carries some of the eggs. In the case of all cardinalfish, the male is responsible for protecting the next generation.

How the Cardinalfish Does It

• When a male and female cardinalfish mate, the female emits her eggs, which the male then fertilizes externally with his sperm. After the eggs are fertilized the male gulps the eggs into his mouth. He continually moves the eggs around his mouth, getting them situated and himself comfortable. While the male incubates he cannot eat, so it's important that he dines well before mating. Males can hold as many as 1,000 to 2,000 eggs in their mouths; the yellow-striped cardinal (Apogon cyanosoma), for instance, can carry well over 1,500 eggs at a time.

Cardinalfish Mating Behavior

• Cardinalfish breeding is rarely witnessed in the home aquarium, as it typically occurs at night. Evidence of spawning will be obvious when the father cardinalfish's mouth suddenly bulges with eggs. The eggs hatch and the fry emerge from the father's mouth about one week after spawning. Any eggs left in the father's mouth two days after the first hatch are generally dispelled, eaten by the father or eaten by other fish. During spawning season cardinalfish will produce a new brood every two to three weeks.

Brooding Cardinalfish at Home

• If you intend to raise baby cardinalfish, a breeding tank should be established as soon as the male's mouth bulge is spotted. The water in the breeding tank should have the same parameters as the primary aquarium. This is most easily achieved by cycling water from the main tank to the breeding tank. Collect the eggs from the male once the first larvae begin to hatch. To do this, catch the father in a net against the tank side, without removing him from the water. He should dispel the eggs from his mouth immediately. Then, he can be released into the tank, while holding the eggs in the net. Carefully transfer the netted eggs to a container with tank water. The eggs should never be exposed to air. Transfer them immediately to the brooding tank. The eggs should hatch within 24 hours of collection from the father. Cardinalfish larvae should be fed marine rotifers until they graduate to larger larval fish foods.