Tropical Fish Hobbyist - October 2010

“The catfish is a plenty good enough fish for anybody,” wrote Mark Twain in Life on the Mississippi. We agree with Twain. True, most cats aren’t bright and flashy like rainbowfish or outgoing like oscars, but here are exceptions. In any case, even the reclusive, mostly nocturnal species have a fascinating range of breeding strategies and behaviors.

Cory Cats

The genus Corydoras is a large group of diminutive South American catfish with elaborate spawning behaviors that science is just beginning to understand. Courting begins in a frenzied chase, with females darting up and down against the aquarium glass while males follow closely, caressing the females’ flanks with their barbels. Scientists who recorded spawning cories with underwater microphones found that male cories use their pectoral fins to make a series of creaking noises during this courtship ritual.

For many species, spawning is easily triggered with a water change using cooler, softer water. Females will scatter the adhesive eggs, attaching them to the aquarium glass and the leaves of plants. The adhesiveness of the eggs is believed to be an adaptation to prevent them from being washed away by current.

Members of the group Scleromystax, within the broader Corydoradinae subfamily, typically deposit all of their eggs in a single mass. Large and very adhesive, their eggs stick to one another in a tight, flat cluster. The eggs are also very hard, almost rubber-like, which may be a defense against predation. In the wild, the production of a large number of eggs increases the chance of survival for at least a few.

around them to ensure a high hatch rate from the usually small number of eggs deposited. Once hatched, the male will keep the fry contained in the secure site until the fry use up the yolk sac and are ready to feed on their own. At that point, which may take up to three weeks, he allows them to exit and face the world on their own. He then sets off to find another ripe female to repeat the process. Females do not help at all tending the eggs and will sometimes even enter a spawn site to eat the eggs of another female.

Driftwood Cats

Tatia intermedia, one of the smaller Amazonian driftwood-type catfish, doesn’t take any steps to protect eggs or fry. When the female lays the eggs, the male is long gone—the female’s eggs are fertilized internally by the male at an earlier time. Unlike many other catfish, she does not hide the eggs strategically in plants or other protective cover.

Resembling a cluster of frog eggs, the eggs are aggregated in a single large mass, each covered in a gelatinous substance that protects them from predators and diseases. The eggs hatch within a day and the fry begin to absorb their yolk sacs while still in their gelatinous covering. After three days, the gel dissolves and the fry scatter for cover. It takes another three days for them to completely absorb their yolk sacs and begin searching for food. No parental care is given, but it doesn’t appear that the adults actively seek out the young to snack on.

Bubblenesting Catfish When it comes to spawning, bettas

David Lass

A male royal farlowella guarding eggs.

Plecos

Fishes in the genera Pterygoplichthys and Hypostomus, commonly called plecos, are incredibly good parents, going to great lengths to protect their offspring. Males in this group of armored, sucker-mouthed catfish select a cave, such as a narrow crack in rock or wood.

After inducing the female to lay her eggs in the cave, the male roosts on top of the eggs and guards them. Using his pectoral fins and expelling water rapidly through his gills, he circulates oxygen-rich water