How to make a hybrid

“Our best chance for a quick impact on hybrid production was to help farmers learn how to make what we call the ‘fry,’ or baby fish, which was new to them,” says geneticist Brian Bosworth.

Bosworth and geneticist Nagaraj Chatakondi are conducting workshops for farmers, in collaboration with MSU scientists, to demonstrate how to produce hybrid catfish fry in hatcheries. They also give on-site consultations at hatcheries.

To produce channel catfish, farmers typically place “spawning cans” in ponds containing mature males and females, Bosworth says. The females lay eggs inside the cans, and the males then fertilize the eggs.

The hybrid catfish, however, is a cross between two different species that do not mate with each other naturally.

Hybrid fry production involves hormone-assisted reproduction. The female channel catfish is given a hormone injection, which induces her to ovulate — release eggs. The fish is anesthetized, and eggs are “stripped,” meaning gently pushed out. Sperm taken from blue catfish males is mixed onto the eggs.

Hands-on training involves teaching farmers the process, ensuring the hormone dosages and egg and sperm preparations are correct, and dealing with any other issues.

“Once eggs have hatched, production is pretty much the same as with regular channel catfish,” Chatakondi says. “The only difference is that hybrid catfish generally grow much faster and are easier to harvest and process. Farmers can increase production 20 to 30 percent by using hybrids instead of channel catfish.”

Still, many farmers prefer channel catfish because fry production costs are lower than those for hybrids, and more channel fingerlings (juvenile fish) are available.

Overcoming inefficiencies in hybrid production

Factors such as inconsistencies in egg quality and sub-optimal hatching conditions increase the cost of hybrid fry production. “We need to find ways to improve efficiency of hybrid embryo production in catfish hatcheries,” Chatakondi says.