Conch herds face death by old age as young molluscs disappear

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A report by Jenny Staletovich for Star 2.

The queen of the sea, a monster mollusk that inspired its own republic in the American state of Florida, is in trouble. It’s now as likely to be found in a frying pan or a gift shop as on the ocean floor. A marine preserve in the Bahamas, famed for its abundance of queen conches, is missing something too: young conches.

Researchers studying the no-take park (where no collection of marine animals is allowed) off Exuma in the Bahamas, one of hundreds throughout the Caribbean, found that over the last two decades, the number of young has sharply declined as adult conches steadily matured and died off.

The population hasn’t crashed yet like it has in the Florida Keys, but in the last five years, the number of adult conches in one of the Bahamas’ healthiest populations dropped by 71%. For the slow-moving slugs that gather by the hundreds to mate, scientists fear a new, unexpected threat may now doom the park’s population: old age.

The discovery also raises questions about the effectiveness of marine preserves, long viewed as a solution to reviving overfished stocks. If one of the Caribbean’s oldest and best marine preserves isn’t working to replenish one of its biggest exports – now regulated as tightly as lobster – what does that mean for other preserves and how they’re managed?

“We can see (the preserve) works for grouper and sharks,” says Andrew Kough, lead author of a study published earlier this year and a larval expert at Chicago’s Shedd Aquarium in the United States. “But for conch that are tied to a complex life cycle of larval dispersal, it’s not working.”

To find out why, Kough and a team of researchers set sail from Miami aboard a Shedd research boat – imagine the Belafonte minus the mini sub in The Life Aquatic With Steve Zissou (2004) movie. The mission is to search for young conches to count and measure and take DNA samples to determine where the conches are coming from.

If they can trace the path of the young conches, the hope is they can find a better way to protect them and manage the fishery.

“The babies are either not coming in in high enough numbers to replenish the adults or there’s something else going on in the park that’s an unintended consequence (of the no-take park),” Kough says. “There are so many sharks and rays inside the park they could just be chowing down on the baby conches.”

In the Florida Keys, the ghost of the conch looms large: in oversized highway replicas, T-shirts, and horns. When treasure hunter Mel Fisher took the throne as king of the “Conch Republic”, he carried a sceptre crowned with a queen conch. But in the Caribbean, conch remains a vital part of the economy, and the reason its governments are so concerned.

Florida Conch Collapse

Conches used to be prevalent in Florida, too. But decades of overfishing nearly wiped them out. In the mid-1980s the US banned their harvest to save what was left. Yet more than three decades later, they still have not recovered in Florida waters, an inauspicious sign for the Caribbean.

Across the Caribbean, conches are as good as currency. Almost anyone who can swim can grab one from the ocean floor and sell it or serve it. Cracked conch or conch salad appears on almost every menu. Their pink-lipped shells line porches and walkways. Countless docks are littered with piles of discarded shells. They are used for everything from jewellery to bait. Whole industries, from fishermen to exporters, depend on a healthy population.

But efforts at regulating them have been uneven. While some islands impose seasons and limits on takes – in the Turks and Caicos conch season starts in October and there are set limits on numbers and size – others have not. Populations have plummeted in Haiti, the Dominican Republic and Honduras, prompting the US to ban their import.

The Bahamas has taken an aggressive approach. In 2013, the government launched a “Conchservation” campaign to save what it considers a national treasure that once gathered in vast herds along miles of flats and seagrass meadows.

In recent years, Kough says those herds have thinned considerably, driving populations down. In the waters around the Berry Islands, he says, previous surveys found the sea bottom littered with conches, which can live up to 40 years and not only hold an important place in the food chain but graze on algae that can kill seagrass. The last time his team visited, Kough says, they found hardly any big adults.

“The fishermen are going further to get the animals,” he says. “We found a lot of sub adults and juveniles as well, but it’s the adults that are in decline, and that just screams fishing.”

Hammered By Harvesting

Scientists believe a healthy population needs between 50 and 100 adult conches for every hectare to sustain itself. The patchier the clusters, the harder it is for populations to find each other and connect.

Working with the Bahamian government, Kough hopes to better understand how the conches are circulating – or more precisely, the baby conches. About five days after female conches release their eggs in long sandy strands, larvae emerge and get caught up in currents.

Because the larval stage can last up to a month, the babies can float more than 160km. Kough suspects the young conches from the preserve are winding up in unprotected areas hammered by harvesting.

Although the Bahamas restricts fishing, Kough says tighter measures may be needed. Regulations currently allow the take of any conch with a flared lip, the smooth curve on its rosy shell that for years has been considered the indication of a mature conch.

Scientists now believe the thickness of the shell is a better measure of maturity, triggering a local move to change rules to require shells be at least as thick as a Bahamian penny. “You don’t want to pull up juveniles. You want animals to reproduce,” Kough says.

Kough is hoping the team can find some answers by studying currents to map the ocean highways travelled by conch larvae. “It’s a lot more complex because the animals are spending so much time out in the open ocean and outside the boundaries (of the no-take park) because they’re dispersing as larvae,” he says. “You can’t create a huge ocean open park. Well, you could, but how would you enforce that?”

The international community has vowed to protect 30% of the world’s coastlines by 2030 to keep fisheries sustainable. But, Kough says, the Bahamas is in the difficult position of having within its borders vast flats and shallows not considered shoreline that should be protected but could exhaust limited resources.

“They recognise there’s a problem. That’s the really important thing,” he says. “So they want to take steps to fix it before it turns into something like Florida, where the population just crashed and still hasn’t recovered.”

 

 

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