Better breeding ability would make catfish farming more efficient and profitable
The $437 million U.S. catfish industry is in need of better genetic and breeding technologies to be competitive with foreign imports. Recently, Auburn scientists have made advances in identifying markers of catfish sperm that can better survive cryopreservation and aid in the selective breeding of high-performing blue catfish.
A team of hatchery scientists from the Alabama Agricultural Experiment Station’s E.W. Shell Fisheries Center was awarded $430,000 by the National Institute of Food and Agriculture to study hybrid catfish breeding practices to help improve reproductive efficiency and reduce production costs for catfish farmers.
“One of my long-term career goals is to have a catalogue of frozen catfish sperm so that the farmer can flip through a catalogue 10 years or 20 years from now and be able to pick what male he wants to use based on criteria that is good for fertility,” said Ian Butts, associate professor and the grant project’s director.
Like most fish, catfish are external fertilizers. During spawning, males release sperm into the water. When farmers breed hybrid catfish, they mimic this environment by mixing sperm from many males. Some males’ sperm will be more successful at fertilization than others. The individual farmer may see this method as a form of hedging to ensure as many eggs as possible are fertilized during the narrow window of spawning season.
However, the method of mixing of sperm means it is nearly impossible to determine which males had the highest performing sperm, making it difficult to selectively breed catfish. The study offers a major step toward developing better breeding practices for catfish, which will greatly speed genetic gains in catfish.
Cryopreservation of catfish sperm has for decades held the promise of helping catfish farmers and scientists develop better genetics, as it has in the beef industry. Yet, it has not been widely adopted among farmers, due in large part to the erratic quality of cryopreserved sperm. Frozen-thawed sperm might perform as well as fresh in terms of fertilization rate, but it also might not perform at all. This has led many farmers to stick to more predictable fresh sperm.
This issue, which scientists are only beginning to understand, is that the qualities that make fresh sperm likely to have a high fertilization rate are not necessarily the same qualities that help it survive cryopreservation. Fresh sperm with a high fertilization rate may see that rate drop dramatically after being frozen and thawed, while other sperm with a similarly high rate of fertilization might survive cryopreservation with no adverse effects.
“Not that many people [in the U.S.] are working in the space of cryopreservation of aquatic organisms—maybe two or three of us at most,” Butts said.
An additional problem is that sperm quality and quantity are likely to change during the lifespan of a catfish, but neither scientists nor farmers know how.
Butts and other scientists at Auburn have begun to investigate this issue thanks to local catfish farmers who donated adult male catfish of varying ages. During the past four years, the team has used commercial aquaculture techniques to collect sperm from catfish and measured how it changed over time.
“This is a massive study…it’s really going to show us how sperm quality is changing as the fish are aging and going through maturity,” Butts said. “The farmer doesn’t really want that variability. They want to be able to take a male of known size and a known age and know it’s going to be a good male. That’s what we need to decipher.”
Taking the guesswork out of selectively breeding catfish will not only help individual producers; it would also be a boon to the U.S. catfish industry, which has struggled in recent years.
“We have to make tremendous gains in order to overcome foreign competition,” said Rex Dunham, the Butler-Cunningham Eminent Scholar in Agriculture & Environmental Science at Auburn and member of the grant team.
In 2007, catfish production in the U.S. suffered what Dunham describes as a “perfect storm” of fuel, feed, disease and recession. The pre-Great Recession economic surge led to fuel prices cresting $4 per gallon in many places, driving up the price of catfish feed and making transport costs untenable for farmers. Ongoing issues with disease plagued the catfish industry during this time. Soon after came the Great Recession, and many catfish producers went out of business. The U.S. catfish production dropped by nearly half, according to Dunham. Cheaper imported Vietnamese catfish rushed to meet the demand and captured a substantial portion of the U.S. market.
Vietnamese catfish farmers have several advantages that allow them to export fillets at half the price of U.S. producers. Both feed and labor are cheap, and the catfish industry is subsidized by the Vietnamese government, according to Dunham. The tropical environment also allows for two crops per year, and the native catfish is a facultative air-breathing species, making them hardier in low-oxygen waters. Vietnamese farmers also face fewer environmental regulations. They divert huge quantities of water from the Mekong River to flush catfish waste, allowing them to grow fish at a greater density than in the U.S., according to Dunham.
Dunham, who has served 44 years at Auburn’s School of Fisheries, was among the group who first cryopreserved catfish sperm. He believes that advances in genetics through cryopreservation and other methods help Alabama catfish farmers better compete against foreign imports.
“Auburn is responsible for a lot of the tremendous increases in efficiency,” Dunham said. “Every little thing we can do to make catfish production more efficient and productive helps ensure the survival of catfish producers’ livelihoods.”
Butts and the team are wrapping up the four-year study by analyzing the copious data collected. Their initial analyses have found two biomarkers in the structure of sperm that predict the sperm’s ability to move, and how quickly—both important to fertilization success. This is a key first step to deciphering what makes a high-quality sperm donor.
“It was a beautiful finding,” Butts said.
In addition to Butts and Dunham, the grant team also included Luke Roy of Alabama Extension and Michael Kjelland of Mayville State University.
