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Project tests technology transfer in soft-shell blue crab aquaculture

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By Milthon Lujan

By: Melissa Schneider*
USA.- Dana Schmidt, an aquaculture facility assistant at Carteret Community College in Morehead City, North Carolina, was chosen to travel south this summer and spend eight weeks working at The University of Southern Mississippi (USM) Gulf Coast Research Laboratory’s Thad Cochran Marine Aquaculture Center (TCMAC) in Ocean Springs, Mississippi.

She drove nearly 900 miles with coolers containing female blue crabs carrying fertilized eggs on their undersides (called sponges by crab fishermen).

The crabs had been screened for diseases and disinfected prior to traveling to Mississippi, and their larvae later grew into juveniles that stocked ponds in North Carolina. The research, part of a $1.1-million, three-year Sea Grant-funded project, aims to transfer existing blue crab hatchery and grow-out technology from Mississippi to North Carolina. The goal: to successfully produce peeler crabs (crabs about to molt) and create a soft-shell blue crab aquaculture industry to help meet demand for the delicacy.

Information exchange

In Ocean Springs, Schmidt spent most of her summer at the marine aquaculture center, where she studied larval culture of blue crabs at the only operational crab hatchery in the United States. She focused on rearing blue crabs and the technologies needed to do it.

Harriet Perry, a research scientist at the aquaculture center and the Mississippi leader on the collaborative project “Expanding aquaculture of soft blue crabs: Technology transfer and cost analysis of pond production and shedding phases,” said Schmidt performed more than her fair share of work at the crab hatchery and took what she learned home to North Carolina.

“She did everything,” Perry said. “She monitored the spawning female crabs and after they spawned, performed daily tasks in the hatchery to keep the larvae alive. She helped create habitat for juvenile raceways, worked on water chemistry, and spent time at the Mississippi Department of Marine Resources’ Lyman Aquaculture Facility in Gulfport where she learned pond maintenance and harvesting techniques.”

Schmidt even spent a few nights sleeping on a cot at the hatchery waking up every hour to check to see if the broodstock crabs had spawned.

The spawned larvae spent a month in the hatchery culture tanks where they underwent multiple molts. After the last larval molt, the tiny post-larval crabs were removed from the culture tanks and transferred to grow-out raceways for juvenile development.

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When the crabs grew to about an inch in carapace width (from point to point), they were harvested, transported to North Carolina and stocked in ponds at Thomas Seafood in Beaufort. They will remain in the ponds until they are peeler crabs of the desired size.

Then, they will be removed, watched until they shed their shells and sold.

Armed with two digital cameras, a cell phone and a lab notebook, Schmidt collected detailed information on blue crab production. Perry and her team trained her on the daily rearing and husbandry requirements that they have developed over the years.

“I plan to pass on what I have learned by training others using this information,” Schmidt said.

Schmidt is combing through her notes, photos and videos to make training materials for students.

“Training has a significant effect on the results of any aquaculture project, even for the most experienced technicians,” she said. “It will take time to develop a team as experienced for reliable results as Harriet’s team. All the information I collected would not be possible without Harriet and her team’s years of dedication and hard work.”

Chuck Weirich, an aquaculture extension specialist with North Carolina Sea Grant, also visited the Lyman Aquaculture Facility. He talked with Greg Crochet, a research associate on contract with USM, who works on blue crab aquaculture efforts.

Weirich and Crochet discussed the project and best practices and tips for maintaining successful ponds. Crochet also instructed Weirich in techniques used to harvest peeler crabs using wax myrtle branches, a folk technique used in the Barataria Estuary of Louisiana called bushlining.

The bushes provide shedding crabs with a place to hide when they are most vulnerable to their cannibalistic pond mates. Crochet also shared ways to keep crabs calm while harvesting, discussed pond predator risks and explained feeding schedules.

Plans for technology in North Carolina

At Carteret Community College, Schmidt and her team (which includes David Cerino, the aquaculture program chair) will purchase equipment and set up a hatchery and grow-out facility with guidance from North Carolina Sea Grant. Students in the college’s hands-on aquaculture classes will help spawn and culture larvae and raise crabs that will be moved to Thomas Seafood in Beaufort, N.C.

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As part of this research project, the seafood company built two quarter-acre ponds that will produce the peeler crabs. Thomas Seafood will shed the peelers and sell them as fresh soft-shell crabs.

Owner Sam Thomas said he relies on local crabbers to supply peeler crabs from the wild. He thinks aquaculture has real potential to supplement their catch.

“I don’t want to cut them out, because they are always going to be an important part,” he said.

He also said there will be a learning curve during the project. It’s his first time working with pond aquaculture.

“I think we have a lot of ifs,” he said. “There’s a lot of things we’re going to learn. Hopefully, if there are any issues, we can overcome them. But, we’ll see.”

David Eggleston of the North Carolina State University’s Center for Marine Sciences and Technology is another project leader. His students will visit the hatchery to observe and help monitor growth in the ponds.

The market

Thomas is hopeful pond aquaculture will allow his business to offer live soft-shell crabs for six to nine months out of the year.

“We do have good markets for our crabs,” he said. “We have some good buyers that we depend on, and we’ve talked to them about the possibility of having crabs available more often throughout the year. Right now, we only shed in the spring because that’s the only time we can get enough peeler crabs here to make turning the tanks on worthwhile.”

He can sell bigger live soft-shells, known as jumbos (5-5.5 inches from point to point) or whales (5.5+ inches) for about $60 per dozen in the early spring.

“If this is successful, I think we’ll see a lot of interest because it will give peeling operations a better year-round supply, and everybody likes that,” he said. “Your restaurants like that.”

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Economic feasibility

Another integral component of this project is determining the costs associated with the hatchery, pond production and shedding phases of soft-shell crab aquaculture. These costs will include operational costs, depreciation, interest on investment, taxes, insurance, labor and more.

Ben Posadas, an extension research professor of economics at Mississippi State University and a member of the Mississippi-Alabama Sea Grant Outreach Team, will lead the cost analysis.

“Assessing the costs of producing soft-shell crabs in ponds is an exciting project to be involved in, one that could ultimately provide a new revenue stream for farmers,” he said. “The economic assessment is an important step before farmers take the plunge into it.”

Perry sees potential for a crab aquaculture industry on the Mississippi Coast as well.

“We do not think it will be a problem to produce and market a quality product,” she said. “We just have to determine the most efficient and cost-effective way to get there.”

* Source: Mississippi-Alabama Sea Grant Consortium

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