The following is a blog post by Dr. Andy Kough, post-doctoral research associate at Shedd Aquarium, about his recent research trip to the Bahamas to study queen conch populations.
At the beginning of June, my colleagues at Shedd Aquarium and I completed five weeks of intensive fieldwork to assess queen conch populations within Marine Protected Areas (MPAs) in the Bahamas. Throughout the trip, we measured the shells of 1,352 individual adult conch, used tow-boards (see right) to visually observe over 170 kilometers of queen conch habitat (and counted 7,176 individual conchs during these tows!) and took 405,882 images of the sea floor to digitally document our work.
The first half of our trip was to the oldest MPA in the Caribbean: the Exuma Cays Land and Sea Park. Here, our Bahamian partners, The Bahamas National Trust (BNT), hosted us at their headquarters where we had easy access to survey large populations of ancient adults that are well-protected from fishing pressure by an onsite warden. For years this population has been thought to be senescing (being made up of more and more old individuals with few young) because heavy fishing pressure has removed the sources of new individuals to the park. However, we were excited to find many sub-adult animals throughout the park from a strong recruitment class in 2013. We hope that it is a sign that the population is rebounding. In addition to using tow-boards to conduct visual surveys of conch, we measured the length and lip thickness of 637 adult conch within the park. The shells of conch grow thicker as the animals age, so we used measurements of lip thickness to tell how old each individual was. We found that the average age of queen conch in the population was indeed older than it had been during previous surveys in 1994 and 2011. These measurements also provided a compelling story when compared with the second half of our field campaign: surveying habitat within conch fishing grounds.
On the second portion of our trip, we spent 11 days on board the R/V Coral Reef II, Shedd Aquarium’s 85-foot research vessel, with partners from the BNT, Cape Eleuthera Institute and Bahamas Reef Environment Educational Foundation (BREEF) to complete surveys over heavily fished and protected areas in the Berry Islands, the Joulter Cays National Park and near Orange Cay south of Bimini. While we found conch in these areas, they were only in the stretches of our survey that were the furthest away from human settlements, and therefore fishermen. Here, we measured the shells of an additional 713 adult conch. The resulting data gave us a comparison between the age and size of conch living in protected versus fished areas.
As has been documented in many species, as fish are heavily exploited the population changes and fish start maturing younger and at smaller sizes. If unsustainable fishing continues for long enough, theory suggests that the traits of the population may shift as the genes responsible for the largest animals disappear. This is especially troubling because the largest animals are often the most fecund, and their removal may increase the time required for an over-exploited population to rebound. So what are we seeing in Bahamian conch populations? Queen conch inside of the Exuma Cays Land and Sea Park’s protection are much older and larger than the conch we found elsewhere. This suggests that fishing may be changing and reshaping the size structure of conch populations around the Bahamas.
Our fieldwork continues to confirm that there is a need for the conservation and protection of queen conch in the Bahamas. As a vital local fishery that provides $4 to 5 million to the Bahamas annually, it’s imperative to find ways to develop sustainable fishing practices so that conch will be plentiful for future generations. We are sharing our research insights with the BNT and other partners, and together we hope to inform sustainable fishery management plans for queen conch in the Bahamas. You can learn more about conservation of queen conch, or “conch-servation,” on the BNT’s website or Shedd Aquarium’s website.
As we return to the Bahamas for more fieldwork on this species, people at home can also do their part to protect queen conch by choosing sustainably sourced seafood. For the most up-to-date information about sustainably caught seafood options, visit www.seafoodwatch.org.