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Sunray Venus clams could be Florida's next big aquaculture crop

Research is being done into the reproductive habits of sunray clams to possibly ramp up their production in Florida.
Published Aug. 13, 2015

ANNA MARIA ISLAND — As labs go, it's not half bad. A blue heron tilts fixedly at the shoreline; dolphin splashes are a brief distraction. Bruce Barber, professor of marine science at Eckerd College, has to squat down to run a blunt knife through the soft, sandy bottom at low tide.

A few assays and it's pay dirt: He pulls up an ovoid 3-inch bivalve, its shell highly polished and radiating with pretty crisscrossed stripes of brown, pink-gray, lavender and gold.

A couple of hundred yards south of the City Pier, Barber is studying a natural population of Sunray Venus clams, or Macrocallista nimbosa. In early July he received an $82,000 grant from the Division of Aquaculture within the Florida Department of Agriculture and Consumer Services for a one-year project sampling this natural population to assess their reproductive habits.

The aim? Promote the clams as a major new aquaculture species in Florida.

All submerged coastal land is state owned. There are more than 280,000 acres of approved shellfish harvesting area in Florida and only 2,250 acres currently leased. That's a lot of untapped real estate.

If things go well, Barber's work will help bivalve researcher Curt Hemmel and his Bay Shellfish Co. bring millions of these clams to market.

This year 6 million have been seeded. Next spring the goal is 10 million.

What's so great about sunrays?

As a restaurant critic, my answer is: everything. Last week I ate a bowl of sunrays next to a bowl of middlenecks at the Sandbar Restaurant on Anna Maria (restaurateur Ed Chiles is Hemmel's partner in Bay Shellfish). They are sweeter and conch-like, meatier, brinier and infinitely more attractive.

Hemmel has a less food-criticky description:

"It is a more mobile animal, like a coquina, therefore it has a larger, meatier foot. And because they live in higher salinity water than many other bivalves, the water gives them a briny taste. They hold their fat throughout the year more than most species of bivalves, and they are also a good candidate to be frozen because (once thawed and cooked) they have a nearly 100 percent rate of opening."

It's not something you can say for most clams.

• • •

When you look at farmed marine species, bivalve farming has proven to be the most successful in developed nations, said Hemmel, who was a pioneer in the state's shellfish industry almost 20 years ago.

While you see plenty of freshwater fish farmed successfully, saltwater fish can be prohibitively expensive to farm due to regulatory issues, labor costs and high feed input costs to grow the fish.

"The main reason that shellfish is a successful model in developed nations is that once they get to a certain size they consume phytoplankton out of the water naturally, which reduces the feed costs and the labor costs," Hemmel said by phone from his laboratory in Terra Ceia.

According to Chiles, 1 percent of the world's aquaculture happens in the United States. He said China is 30 years ahead of us; Hemmel said Europe is even further ahead in shellfish culture research.

They both enumerate the benefits of ramping up sunray production: a locally produced, sustainable source of high-quality seafood; a boost to the local economy in the shape of farming, processing, harvesting and gear manufacturing jobs; and the ecological benefits of having more filter feeders in the coastal environment.

The holdup is where Barber comes in.

"With bivalves the mysteries are temperature and food. The problem is not knowing the secrets of the sunray's reproduction," he said, making his way back to the shore on Anna Maria clutching a mesh bag of wild clams.

Having started at the University of South Florida's marine science department, he spent 10 years at the University of Maine studying bivalves. He said a lot of academic work doesn't have relevance to industry.

But if Barber can nail down exactly what and when this native species likes to eat, at what temperature it thrives and when it spawns, Hemmel can use that information to increase production of seed, keeping them alive until they reach the 5-millimeter size when they are sold to farmers and put out in the field.

This time there's relevance.

• • •

For now, sunrays are a drop in the Florida clam bucket. A Florida aquaculture survey indicated that the state's clam sales in 2012 totaled $11.9 million, with 256 million seed planted and 136.3 million clams sold. Of that number, 98 percent were hard clams.

Hemmel produced his first commercial sunrays in 2008. He said it fits with Bay Shellfish's core mission.

"We look at ourselves as a problem-solving company," he said. "And certainly in bivalves the challenges are to continually reduce costs, produce a high-quality product and to bring new species online."

At this point, sunrays are about twice as expensive as hard shells. Hemmel said some of this is because, from a hatchery standpoint, they cost more to produce, but that "any new species comes out at a higher price, and lowers upon economies of scale." Sunrays grow faster than hard clams, he said, reaching the optimal 2-inch harvest size in about a year, whereas hard shells are up to six months longer to harvest.

It will be another year before Barber's water samples and tissue slides yield their secrets under the microscope. But Hemmel has no doubt about the commercial viability of the sunray.

"It's a local species and it's uniquely delicious."

And Chiles is certain that the southern part of Tampa Bay is the place to grow them.

"Water temperature, water quality and nutrient levels — this is ground zero for clams right here," he said. "Cedar Key is a thimble."

It is through this unusual public-private partnership that innovation is possible.

"Elon Musk wants to put people on Mars," Chiles says. "I want to bring aquaculture to the Everglades."

Contact Laura Reiley at lreiley@tampabay.com or (727) 892-2293. Follow @lreiley on Twitter.

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