Student assistant Ian Bouyoucos examines a blacktip shark as part of the National Oceanic and Atmospheric Administration’s Virgin Islands shark research project. NOAA is gathering important data regarding shark nursery habitats in the territory.
The shallow bays found around St. John provide the perfect place for several species of sharks to avoid predation until they are big enough to enter deeper waters, making the island integral to sustaining shark species.
The National Oceanic and Atmospheric Administration, which has been conducting research around the territory to learn more about the shark populations utilizing local bays, presented its findings on Thursday evening, June 10, at Maho Bay Camps.
Shallow bays are ideal places for shark nurseries, as sharks offer no postnatal care to their young. The mother takes off right after birth, leaving young sharks to fend for themselves.
“Shark nurseries occur in shallow near-shore habitats, and they’ll spend a lot of time there for the first couple years of their lives,” said Bryan DeAngelis of NOAA at the June 10 presentation. “People are beginning to hypothesize that shark populations are limited highly by just how much available habitat there is.”
Most predation of baby sharks is done by adult sharks, making shallow waters — where larger sharks can’t swim — the best place for sharks to spend their first few years. There’s also an abundance of food in shallow areas, which is important to young sharks who need a lot of energy, DeAngelis explained.
“Despite all other pressures such as over fishing and offshore harvesting of fins, if there’s not enough habitat for shark nurseries, the population may not be able to sustain itself,” he said.
Shark regulation in the Virgin Islands falls under the federal Fishery Management Plan for Sharks of the Atlantic Ocean; however, federal management alone may not be enough to sustain the health of local shark populations. When DeAngelis and NOAA began their quest, it was discovered that collection of local data was very difficult and sufficient enforcement was lacking.
“Nobody had ever done a survey that said who was here and what type of habitat they were using,” said DeAngelis. “Before we could concentrate on learning more about nursery areas, we needed to document who was here.”
The NOAA team documented blacktip, blacknose, Caribbean reef, Caribbean sharpnose, hammerhead, tiger, lemon and nurse sharks around the Virgin Islands. DeAngelis and his coworkers utilized acoustic hydrophones to track sharks in shallow bay nurseries.
Sharks are captured and in just a few minutes, a transmitter is surgically implanted inside the fish before it is released into the ocean.
“The transmitters emit an acoustic ping which is picked up by acoustic hydrophone receivers at the bottom of the ocean,” said DeAngelis. “The receiver stores the date and time of the ping, and you can start to get an image of what habitats the sharks are using. You can really start to expand your knowledge of these guys and how they’re using the area.”
NOAA must now begin to analyze the thousands of pieces of data collected by the receivers. DeAngelis hopes to answer questions including how long are sharks staying in the bays, how strong is the site fidelity, and what are the emigration and mortality rates. He also hopes to investigate connectivity of populations in different bays.
DNA is also being collected from sharks in the hopes that information will eventually be used to further determine relationships between different nurseries.
While St. John bays do provide ideal habitats for shark nurseries, people should not be concerned about being attacked while in the water, DeAngelis explained.
“We work all day just to find a couple of sharks,” he said. “The ones we do find are really, really small babies and they’re really, really scared of people. Take it from me, a very frustrated person who will watch a shark swim around a piece of bait for hours before it decides it wants to take it: there are no sharks in these waters that we need to be afraid of.”