A new survey technique provides insight into Queen Conch populations off the islands of Anguilla, St. Eustatius and within the Saba Bank. This research offers new information concerning Queen conch population distribution, useful for management authorities. Queen conch population in the Caribbean in general have been decimated by intense fishing pressure so improving surveying techniques will aid in their overall management in the region.
Queen conchs (Aliger gigas) are an iconic species of the Caribbean, representing both economic and cultural importance. Unfortunately, these species are heavily exploited, as their meat is popular in local cuisine and their shells are popular decorative pieces. Historically population data for Queen conch were gathered using dive surveys, however, these can be logistically demanding and expensive and limited to depths accessible to divers. Luckily, a new collaborative study by Wageningen University and Research, Chicago’s Shedd Aquarium, Van Hall Larenstein University of Applied Sciences and the Royal Netherlands Institute for Sea Research worked to improve these population estimates by implementing a novel towed video system.
Through combining traditional dive surveys with the towed video system, researchers can now explore species abundance to a depth of 60 m. In addition, this method allows new relationships between environmental variables and conch abundance through this range which had previously been poorly studied. It is understood that Queen conch move to deeper waters as they mature, so being able to document these deeper depths will give researchers and managers a more complete view of conch populations.
Surveys were conducted throughout three different locations: Anguilla, St. Eustatius and within the Saba Bank. Saba Bank was found to have the highest overall mean conch density, with an average of 126 conch per hectare, and ranged from depths of 16 m to 50 m. St. Eustatius was found to have a mean density of 62 conch per hectare, ranging from depths of 11 m to 45 m. For all three locations the highest densities of conch were found in water deeper than 25 m, with densities of 393 conch/ha at depths greater than 40 m on Saba Bank and 285 conch/ha at depths greater than 30 m on St. Eustatius.
In general, this study found patchy distribution patterns of adult conch, likely due to aggregating behavior during spawning events. Other environmental factors, such as algal cover, distance to the open ocean and depth were also shown to impact conch abundance. Depths between 17 and 45 m were shown to have the greatest number of reproductive conch, highlighting the importance of safeguarding these areas to protect the reproductive capacity for these populations in the future.
With this new information, management authorities can now focus their attention to areas likely to host Queen conch populations. Researchers from this project recommend that future Queen conch surveys operate over a range of depths while sampling a variety of bottom conditions. These results can then be analyzed to better understand the connection between the conch distribution and local or regional factors. Although each island may require their own approach, this study highlights that many of these factors may be universal and should be considered when designing future campaigns.
There is still much to be learned about Queen conch, such as the impact of algal cover or shifts in seagrass densities and species on their foraging behaviors. Gaining a holistic understanding of local conch populations will aid in the design and implementation of effective conservation projects moving forward. To learn more about this project, you can find the published article on the Dutch Caribbean Biodiversity Database by using the link below.
Report your sightings
Have you observed an Queen conchs? Report your nature sightings and photos on the website DutchCaribbean.Observation.org or download the free apps (iPhone (iObs) & Android (ObsMapp)). Species reports by local communities and tourists are invaluable for nature conservation efforts to help increase public awareness and overall species protection. Besides, DCNA, Observation International and Naturalis Biodiversity Center are working together to develop on automated species identification app for your phone. Your uploaded photos are of great value to make this possible. For questions, please contact research@DCNAnature.org
You can learn more about this research by reading the published article on the Dutch Caribbean Biodiversity Database using the button below.
More info in the Dutch Caribbean Biodiversity Database