CHICAGO, United States (CMC) — A new study has found that the population of the queen conch, an iconic Caribbean marine snail, has declined significantly over the last two decades due to overfishing.

The study found that even when individual populations are well-protected within marine sanctuaries, their long-term viability may be in doubt.

The study published in the journal Marine Ecology Progress Series, suggests that a network of connected marine parks would better protect conch into the future.

Researchers from Shedd Aquarium, University of Miami and Community Conch studied protected queen conch, Lobatus gigas, within the Exuma Cays Land and Sea Park (ECLSP).

Established in 1958, the ECLSP was the first Marine Protected Area (MPA) created in the wider Caribbean and is famous for its pristine environments.

While it bans fishing, shelling, conching and lobstering within its borders, and protects various habitats from seagrass and mangroves to coral reefs and stromatolites, recent surveys and historical data suggest its conch population may be in trouble. While individual animals are living to older ages, new generations of conch are less prevalent and the average age of the population has been increasing for decades.

“The queen conch is considered a national conservation concern in The Bahamas as a popular culinary staple and valuable export commodity and thus, the people and government have taken steps to protect them,” said Dr Andy Kough, postdoctoral researcher at Shedd Aquarium who led the study.

“However, our research serves as a reminder that not all protected populations are self-replenishing and that the success of a MPA can depend on processes outside of its borders. These results demonstrate the importance of continued monitoring to assess MPA efficacy and show how the biology of a species inherently affects its distribution in the oceans.”

Researchers collected data describing conch abundance and age. To measure abundance, researchers used tow-boards to conduct visual surveys of conch while being towed behind small boats. In addition to visual surveys, researchers measured the population’s relative age by free-diving to the seafloor and bringing conch aboard their boat.

There, they measured the length and lip thickness of the conch before returning them to the ocean. By comparing surveys with 22 years of historical data, the study authors were able to track how the population is doing and showed that the average age is increasing.

“In theory, effective MPAs preserve an ecosystem by reducing human-related impacts from affecting the species within its borders,” Kough added.

“Species within an MPA should thrive, spill over and replenish the unprotected areas surrounding it, anchoring the ecosystem as a whole. However, it is challenging to protect animals with complex lifecycles, especially in marine species like the queen conch, because most have a free-floating larval stage that can last for weeks to months.

As such, animals transitioning from larvae to a juvenile are often a long distance away from where life began because of ocean currents and tidal cycles. The park is home to the highest abundance of conch in the Exumas because of the diligent work of the park staff, but without larvae from populations outside of the protected area it may dwindle and disappear,” he added.

By nature, a conch is a slow-moving snail that does not move large distances as an adult. When it comes to breeding, this means the animal is more likely to find a mate in a location with high densities of other conchs.

Areas with fewer conchs have little to no breeding and must rely on other areas to replenish the population and supply the next generation. If the source of larvae is missing, even a very well-protected population, like the ECLSP, may slowly die off.

The Bahamas National Trust has launched a national “Conchservation” campaign with conservation partners, including Shedd Aquarium, aimed at protecting queen conch in The Bahamas through research, citizen science and policy change. The plight of the conch has even inspired Bahamian artists to record a song and produce a music video.

“As conservation efforts continue in The Bahamas, Shedd looks forward to monitoring conch within the ECLSP and throughout The Bahamas in order to help inform a science-based management policy for the species,” said Kough.