Conchs mostly gone from Florida. Can the Bahamas save them?

number of young has sharply declined as adult conchs 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 conchs in one of the Bahamas’ healthiest populations dropped by 71 percent.

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 over-fished 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,” said Andrew Kough, lead author of a study published earlier this month and a larval expert at Chicago’s Shedd Aquarium. “But for a lot of the animals you don’t consider as much, for example 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 this month from Miami aboard a Shedd research boat — imagine the Belafonte minus the mini sub in “The Life Aquatic with Steve Zissou.” For 12 days, they’ll dive the deep channels surrounding the park in search of young conchs to count and measure. They’ll also take DNA samples to determine where the conchs are coming from. If they can trace the path of the young conchs, 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,” Kough said.

In the Florida Keys, the ghost of the conch looms large: in oversized highway replicas, T-shirts, and horns. But in the Caribbean, conch remains a vital part of the economy, and the reason its governments are so concerned.

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

Across the Caribbean, conchs are as good as currency. Almost anyone who can swim can grab one from the ocean floor and sell it or serve it.

But regulating them as been uneven. Some islands impose seasons and limits on takes, but others do not.

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.