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Connecting the Conchs in the Bahamas

Queen conchs, giant marine snails critical to the economy, cuisine and culture of the Bahamas, have nearly disappeared. To aid their recovery, Shedd is conducting research on where the floating juveniles of this important snail species settle and begin to grow. The results will inform conservation and management strategies to help create a sustainable conch fishery for future generations.

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Adrift, then settled

Like many other marine species, queen conchs begin their lives as planktonic larvae that disperse on ocean currents. At about a month old, and as far as 100 miles from where they hatched, conchs end their larval journey and settle into shallow nursery habitats. Here the snails begin building the familiar spiked-and-spiraled shell and leading a much less mobile life.

Conchs take years to mature and reproduce. The best indicator of a conch’s age is the thickness of its shell. A conch with a shell 15 millimeters, or about half an inch, thick is likely reproductively mature. But conchs are often collected by fishermen before they grow to that size. Reproduction, and therefore replenishment of conch habitats downcurrent, can’t happen if overfishing reduces the density of adults to the point where they can’t find each other to mate.

“Marine protected areas are a fantastic conservation tool because they protect very large, dense areas, which can then resupply and replenish depleted populations in other areas.”

Andy Kough, Ph.D., research biologist
A small motor boat pulls a diver on a long tether in the Bahamas, the diver scanning the sea floor for conch.
A wild conch sits among sea grass in the bahamas, the slug inside barely visible through the opening in its iconic large shell.

Mapping connectivity

Shedd scientist Andy Kough, Ph.D., and his team are building our understanding of conch populations by collecting data on remaining adult populations. Using Shedd’s research vessel as a basecamp in the Bahamas, they survey remote seagrass, hard-bottom and sand flat habitats to count conchs and measure density.Gripping the handles of a camera-equipped tow board pulled by a small motorboat, they dive beneath the surface to count conchs and take photos to describe the ecosystem beneath them.By mapping adult populations, Shedd scientists can use computer models to combine data about currents, seafloor topography and conch biology to simulate the movements of juveniles, helping to predict where they may need to be protected as they grow

Goal: Saving conch and eating it too

Queen conchs have been collected at a sustainable level by local subsistence fishers for centuries. Beginning in the 1970s, however, increasing commercial fishing has caused conch populations to decline or collapsed in much of the species’ range in the Caribbean, Gulf of Mexico and Bahamas.

Shedd scientists are are partnering with the Conchservation Campaign, a group of not-for-profit organizations spearheaded by the Bahamas National Trust, to develop science-based management strategies for queen conchs. By looking at the effectiveness of protected areas, the health of existing populations and the dispersal patterns of juveniles, we can inform improved networks of protected areas to replenish stocks of conch and other species.

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