Scientists Document How Marine Protected Areas Can Help Restore Declining Populations
After a 2018 review of queen conch populations in The Bahamas indicated rapid declines, a new research study brings hope for how to save the imperiled marine snail’s future. The study was published in Conservation Science and Practice by a research team led by Chicago-based Shedd Aquarium and shows that conch within a well-enforced Marine Protected Area (MPA), an area where fishing is banned, reproduced and replenished populations of queen conch within fishing grounds. The results highlight the importance of MPAs beyond their borders, and the study suggests where to expand a network of protected areas within The Bahamas to benefit queen conch populations across the island nation.
“In many parts of The Bahamas, conch have been overfished, however, hope remains,” said Dr. Andy Kough, research biologist at Shedd Aquarium and lead author on the paper. “Our research unequivocally demonstrated that conch protected within a no-take park replenished nearby populations as they reproduced and their babies, called veliger larvae, spilled over into non-protected areas. If some areas where adults are abundant enough to breed are protected, they can help ensure a healthy environment and thriving fishery with conch for years to come.”
The way conch reproduce connects distant conch populations, which is the reason an MPA can replenish a population outside of its borders. After finding a mate, an adult, female conch lays eggs that hatch into larvae and then float for many miles in ocean currents. Therefore, breeding adults within the borders of an MPA can send larvae over the park’s boundaries, despite being relatively immobile themselves because of their heavy shells.
To confirm this was occurring, the research team studied both adults and larvae using two different and complimentary techniques: SCUBA surveys to collect information on the size, age and abundance of adult conch; and a computer program to estimate where larvae are dispersed over a wider range. The study area included a Bahamian MPA called the Exuma Cays Land and Sea Park.
The team was looking to answer two key questions: do MPAs replenish adjacent populations of queen conch, and how are distant populations of conch connected in the Exuma Sound, a deep body of ocean adjacent to the MPA and where fishing is permitted?
There were three key research findings:
- There are three times as many adult conch within the MPA.
- Effective MPA enforcement by Bahamian officials resulted in conch that were bigger and older.
- Larvae that originated from the MPA settled in unprotected areas outside of its borders, including fished sites with densities currently too low for reproduction.
“Collecting data on the conch populations inside and outside of the Exuma Cays Land and Sea Park is important, but we also recognize that it is equally important to bring in the historical knowledge and perspectives of Bahamians,” said Kough. “After all, conservation efforts depend on the participation and buy-in of local communities to be successful.”
The Bahamas National Trust conducted surveys of fishers’ opinions on the status of queen conch populations in nearby islands and the perceived need to take action. The study describes how fishers acknowledged that the fishery is in trouble with fewer conch than there used to be, but in some cases, they doubted the utility of MPAs. This was due in part to few local examples of successful MPAs.
“During our conversations with communities and fishers, we heard that conch are harder to find these days, and – most importantly –people want to help them rebound,” said Agnessa Lundy, marine science officer at the Bahamas National Trust and a co-author of the study. “We all want to leave a legacy for our children that includes conch – on the seafloor and on the fry. Our study shows that parks can help make that future a reality, when combined with changes in regulation and enforcement that keep away foreign poachers and keep the playing field level for Bahamian fishers.”
Based on the noted success of the Exuma Cays Land and Sea Park and the desire of Bahamians to help conch bounce back, the study suggests locations for future MPAs, such as between the Exuma Cays Land and Sea Park and Great Guana Cay. The suggested locations were determined using the open-source Connectivity Modeling System of the Rosenstiel School of Marine and Atmospheric Science (RSMAS), a tool that estimates the long-distance travel of conch larvae and how marine ecosystems are connected to one another. The new additions would establish a network of MPAs within Bahamian waters.
“As larvae are transported by the ocean’s currents, there needs to be strategically placed marine protected areas that safeguard the sources of larvae that are replenishing other populations in fishing grounds,” said Claire Paris, co-author and professor in the Rosenstiel School of Marine and Atmospheric Science at the University of Miami. “Based on how marine ecosystems are connected in The Bahamas, we know a network of well-enforced MPAs can provide stability to conch populations by ensuring a consistent larval supply. Our study uses a successful example to strongly support the use of MPAs as a conservation tool.”
The study, “Ecological spillover from a marine protected area replenishes an over-exploited population across an island chain,” was conducted by a research team including scientists from Shedd Aquarium, the Bahamas National Trust, Community Conch, Humbolt State University, the University of Miami, Old Dominion University and the Gulf of Maine Research Institute.
The findings build on previous research published in Reviews in Fisheries Science & Aquaculture in October of 2018 that suggests the Bahamian conch stock is on a trajectory for serial depletion if regulatory and conservation measures are not taken. The recommendations also come after the country made a commitment to designating 20 percent of Bahamian waters as protected areas by 2020.
For more information about queen conch, visit the Bahamas National Trust’s educational Conchservation website. And for more information on Shedd Aquarium’s conch research studies, visit Shedd’s website.
PHOTOS: High resolution photos of queen conch from The Bahamas are available for download:https://personal.filesanywhere.com/fs/v.aspx?v=8d72628a59656db66ba4
©Shedd Aquarium/Sam Cejtin
VIDEO: High resolution b-roll footage of Shedd Aquarium’s queen conch research is available for download:https://personal.filesanywhere.com/fs/v.aspx?v=8d72628a596570a5b168
©Shedd Aquarium/Sam Cejtin