Researchers are poring over more than 100 hours of footage recorded using baited underwater camera traps as part of a study of the island’s shark populations.
The data, collected last month on a network of 52 cameras strategically stationed at 13 survey sites around Grand Cayman, will help scientists build a picture of the distribution of sharks around the island.
Caribbean reef sharks, nurse sharks and blacktip sharks have all shown up on the footage so far.
Johanna Kohler, shark project officer, said the team would spend the next two months analyzing the data. She said similar surveys were conducted on Little Cayman earlier this year.
The information helps fuel conservation management strategies for sharks, which are now a protected species in Cayman’s waters under the National Conservation Law.
“We are currently working on an estimate of our local shark population. But even without an actual number, it is safe to say that we have fewer sharks in Cayman than we need for a healthy reef,” Ms. Kohler said.
“In light of the general global decline of shark populations, it is important to keep an eye on our local shark population.
“Monitoring population trends allows us to assess long-term trends and patterns and potentially respond quickly to declines by altering management approaches in order to deal with conservation issues.”
The Baited Remote Underwater Video system uses camera traps to attract sharks, which are generally shy animals.
A mesh bag of bait attached to an upside-down crate creates a plume of chum, which brings predatory fish, including sharks, into the camera’s field of view. Moray eels, turtles and stingrays have also shown up to investigate.
The camera records continuously for two hours and the footage is analyzed back on land to provide survey data. Four camera traps record at 13 sites around the island to provide a snapshot of the shark population.
Researchers also log data points during recording, including wind speed, cloud cover, wave height, depth and the strength and direction of the current. The surveys are carried out twice a year in Grand Cayman.
“The standardized approach makes the results statistically comparable site to site and year to year so that we can detect meaningful changes in shark populations,” Ms. Kohler added.
The BRUV survey is part of Shark Conservation Cayman’s ongoing shark research program, which is a collaboration between the Department of Environment and Marine Conservation International. The program has been studying sharks in Cayman since 2008 and the continued research now relies entirely on private funding, including from its main sponsor, CayBrew.
Other research methods include acoustic tags and a network of volunteer divers who log shark sightings.
Ms. Kohler added, “Our research goal is to improve the understanding of our local sharks to develop better ways to protect and conserve them and to share the knowledge with local communities.”