Shedd Scientists Are Helping Caribbean Icons Rebound

Queen conchs (Lobatus gigas) are large herbivorous snails that move so slowly that plants and corals colonize their shells—camouflaging the vulnerable snails as microreefs. The underside of a conch’s foot-long spiny, whorled shell has a glossy pink-orange finish and dramatic flared lip. Using a powerful fleshy foot, these slow-moving mollusks can “leap” across the seafloor in warm, shallow waters in search of a bite of algae or a breeding partner.

Nassau groupers (Epinephelus striatus), which can reach a length of 4 feet and weigh up to 50 pounds, are migratory reef fish that can travel hundreds of miles when moving between feeding and spawning habitats. Throughout most of their range, near the full moon from November to March, these ambush predators come together in large “spawning aggregations” that have historically numbered more than 100,000 individuals.

Despite their differences, both species face substantial population declines for the same reasons: They predictably breed in great numbers at known locations and are relished cultural delicacies, subjecting them to rampant overfishing.

Nassau groupers once made up one of the most important reef fisheries in the Caribbean. Shedd research has shown, however, that at least one historic spawning aggregation has been completely wiped out. The Nassau grouper is classified as critically endangered by the International Union for the Conservation of Nature Red List and as threatened under the U.S. Endangered Species Act.

Queen conch harvests provide massive commercial and cultural value to the Bahamas as their second-largest fishery. In some places, Shedd research has suggested that queen conch populations in the Bahamas have decreased by 90 percent since 2009. This troubling trend further supports the iconic mollusks as a candidate species for the U.S. Endangered Species Act. The U.S. Fish and Wildlife Service has tracked and restricted trade of queen conch as a protected species since 1992. Yet both conchs and groupers remain ecological, economic and cultural keystones of the Bahamas.

To reverse the decline of these important species, Shedd scientists study their behaviors and survey population changes over time. They use a variety of methods including acoustic telemetry, scuba surveys with underwater cameras, computer modeling and genetics. Shedd’s 80-foot research vessel, the R/V Coral Reef II, facilitates fieldwork for Shedd scientists and collaborators in the Bahamas. The data collected are crucial to guiding conservation efforts to protect these keystone species, ensure a sustainable commercial future for the local fisheries and enable a cultural heritage for future generations.

Conch protections beyond borders

Shedd’s queen conch expert, Andy Kough, Ph.D., worked with research partners to study the effectiveness and local perceptions of marine protected areas (MPAs) as a solution to declining conch populations in the Bahamas. In a series of town hall meetings and interviews, Bahamian fishers agreed that government intervention was necessary to protect conch fisheries, but many expressed concern that MPAs only provided “fairytale benefits.” Andy’s research has shown the opposite.

In summer 2017, Andy’s team performed dive surveys in the Exuma Cays to collect data on conch abundance, distribution, size and age. The team found more adult conchs that were both living longer and growing larger within the MPAs than animals outside the protected areas. In other words, the reserve worked at protecting adult conchs. Even better, conch larvae from inside the MPAs were shown to be transported beyond the borders of the protected areas to distant nursery grounds that supported fishing. Their results demonstrate the efficacy of marine protected areas to not only protect queen conchs from overharvesting but also to replenish fisheries for a sustainable future.

Groupers bounce back

As in most places in the Caribbean, Nassau grouper populations had collapsed in the Cayman Islands by the 1990s due to overfishing. Concerns raised by Caymanian fishers, however, coupled with the discovery of a small spawning aggregation on the west end of Little Cayman, sparked a renewed interest in protecting the imperiled reef predators. For more than 15 years, a research and monitoring program, Grouper Moon Project (a collaboration of the Cayman Islands Department of Environment and the Reef Environmental Education Foundation) has worked to monitor and evaluate conservation strategies including seasonal fishing bans and the protection of spawning aggregation sites. Yet whether a healthy and breeding grouper population could recover from extremely low numbers remained unknown.

To investigate whether the conservation measures were working, Shedd research biologist Lynn Waterhouse, Ph.D., helped develop and implement a long-term (2005-present) dive survey program to enumerate populations of Nassau groupers at their spawning aggregations off the islands of Little Cayman and Cayman Brac. Using video survey counts coupled with radio-tagging and resighting data to create an integrated population model, Waterhouse and colleagues found that grouper abundance had more than tripled at Little Cayman with a similar trend emerging at Cayman Brac. Their findings provide strong evidence that long-term seasonal and spatial protections of grouper spawning aggregations work as an effective conservation tool, but that recovery takes time.

For both the queen conch and Nassau grouper, Shedd research showcases how conservation measures like MPAs and fishing regulations can help overfished populations rebound. By establishing science-based regulations, policies and protections, we can begin to ensure a sustainable future for marine species and the people who depend on them.

You can help by making sustainable seafood choices. And you can support critical conservation research by joining Shedd’s mission to preserve and protect the aquatic world.

—Lucas Chamberlain, science communications fellow