If larval exchange is key to conchs’ sustainability, then knowing the dispersal pathways, or connections, among populations is key to their conservation.
To trace this connectivity, Andy and his team, which includes other researchers as well as citizen scientists, must first collect data on adult conch populations during the peak breeding season. Using Shedd’s research vessel as a basecamp in the Bahamas, they survey remote seagrass, hard-bottom and sand flat habitats to measure conch numbers and density. To cover a lot of ground quickly, the researchers use a method that’s a cross between snorkeling and sledding. Gripping the handles of a camera-equipped tow board that’s pulled by a small motorboat, they dive beneath the surface to take high-resolution photos that can be digitally pieced together into a mosaic map with crisp images of conchs, vegetation and other animals in the community.
The next step is to determine dispersal pathways. While divers can’t follow microscopic larvae through the ocean, computer tools can process data about currents, seafloor topography and movements of particles the size and shape of the larvae to create a biophysical model of those pathways. More fieldwork can confirm whether juvenile conchs are present in predicted areas.
Armed with this information, along with known fishing pressures, Andy can then recommend management strategies for the conservation of conchs. Andy’s research is in partnership with the Bahamas National Trust, Bahamas Department of Marine Resources and Community Conch, a not-for-profit organization dedicated to protecting the queen conch in the Bahamas.
Goal: Saving conch and eating it too
Queen conchs have been collected at sustainable levels by local subsistence fishers for centuries. Beginning in the 1970s, however, a commercial fishery developed for international markets, dominated by the United States, and for a growing tourist trade. Landings (the weight of the conch catch brought ashore) tripled within 20 years. Since then, landings have steadily declined as conch populations have been overfished, yet demand for conch meat remains high.
Creating a network of protected areas encompassing both where the larvae come from and where they settle, in tandem with implementing a science-based management plan, is a proven method of reestablishing healthy populations of benthic, or seafloor-dwelling, species. The connectivity study could inform the placement of new marine parks in the Bahamas. The parks would restock each other with new larvae, and as populations grew, an eventual overflow of adults into adjacent fishing grounds could once again support a sustainably managed harvest of the gastronomic gastropod aptly named queen conch.