On a cold April morning, a group of men gathers at a cluster of catfish ponds. Two use tractors to slowly pull a wide net though each pond while others, in waterproof gear, scoop fish from the chilly waters for research at the University of Arkansas at Pine Bluff.
Inside a mobile lab, research associate Neil Pugliese holds a small, live catfish in a cooler of murky water and guides a probe along its pale belly. Alf Haukenes peers at the image that immediately pops up on his laptop computer.
The grainy black and white image on the screen looks familiar to anyone who has taken a peek at an ultrasound of a human baby.
“What you’re seeing here is the inside of the peritoneal cavity,” explains Haukenes, a researcher with the UAPB Aquaculture/Fisheries Center, describing the fish’s abdominal area. “I’m not seeing any ovary development in this fish.”
While an ultrasound exam is usually associated with pregnant human mothers, it can also be used to get an up-close look at fish. The pictures speak volumes and could benefit hybrid catfish producers, he says.
The ultrasound technology allows researchers to look at eggs inside fish and can be used to determine gender if the fish is mature enough.
“There are some aquaculture uses and some natural fisheries uses,” Haukenes says, explaining that the tool could aid farmers fishing for a way to boost the breeding of male blue catfish and female channel catfish.
“There’s an interest in hybrid catfish which have to be artificially spawned. One challenge is to use this tool on smaller and smaller fish to distinguish males and females.”
Hybrid catfish have many desirable qualities including being more resistant to diseases, having more meat per fish, and being more resilient as a breed.
“What the ultrasound does is allow you to look inside the female channel catfish to see if she is close to spawning or not,” Haukenes says, adding that more distinct images of individual eggs suggest different stages of development and signal how close the fish is to spawning.
Ultrasound technology could also be a non-invasive way of determining the gender of catfish at a relatively early age and that would allow for easier sorting of males and females for future breeding or hybridization. Haukenes’s goal is to develop procedures for Cooperative Extension specialists who will, in turn, share them with farmers to help in selecting brood stock.
An assistant professor in applied fish reproductive physiology at UAPB, Haukenes has been collaborating with colleagues at Louisiana State University, who have also been using the technology. His research project is funded by the Arkansas Catfish Promotion Board.