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Designing Shark Sanctuaries in Belize on the World's Second-Largest Barrier Reef

PIs: Drs Ellen Pikitch and Demian Chapman, Institute for Ocean Conservation Science, and Dr. Beth Babcock, University of Miami

Long-term Monitoring of Sharks at Glover’s Reef
Shark Movements in Relation to MPA Boundaries
Remote Video Survey of Sharks Across the Belize Barrier Reef

Many shark populations in the Atlantic Ocean are collapsing as a result of unsustainable fishing, and there are grave concerns that Caribbean sharks face a similar fate. The demise of these beautiful and ancient animals would be not only an inherent loss, but would also disrupt the balance of undersea food webs, hasten the widespread decline of coral reef health, and jeopardize the eco-tourism industry.

On the Mesoamerican Barrier Reef (MABR) in Belize, which is more than 600 miles long and is second in size only to Australia’s Great Barrier Reef, the government is actively establishing a network of Marine Protected Areas (MPAs) spread across 600,000 acres and designed to protect the reef ecosystem. While MPAs are a potentially effective management tool for fish that have sedentary lifestyles, there has been very little scientific research on how well they can protect highly mobile sharks that could move outside of MPA boundaries on a regular basis.

The Institute for Ocean Conservation Science shark research team has since 2000 studied the sharks of the MABR, with a special focus at Glover’s Reef atoll. Glover’s Reef is one of only four atolls in the Western Hemisphere and is one of the largest MPAs in the Caribbean. The team has discovered through careful observation and tracking that populations of large apex predatory sharks – such as Caribbean reef sharks and nurse sharks -- have remained robust at this offshore atoll even while populations in neighboring waters continue to decline. Our long-term studies are proving that the sharks’ success here is directly related to the unique design of the Glover’s Reef MPA. We are now expanding our shark monitoring to the entire MABR, using remote video surveying technology. As we gain greater knowledge about shark population trends throughout this ecosystem, we will help the Belizean government expand their shark conservation success at Glover’s Reef to the entire MPA network.

Dr. Ellen Pikitch and Demian Chapman releasing Caribbean reef shark, Glovers Reef Atoll.
Photo by Tim Calver

Long-term Monitoring of Sharks at Glover’s Reef

Up until 2000, nothing was known about sharks’ biodiversity, breeding area locations, or population trends in Belize. Dr. Pikitch changed this by initiating what would become a decade-long shark survey and monitoring project at Glover’s Reef. Since 2000, researchers have been periodically setting out “baited longlines,” each containing up to 70 hooks, to catch sharks for sampling. All hooked sharks are brought alongside the research vessel, identified, measured, tagged, and released. A DNA sample is also taken from each shark’s fin for later analysis. This work has identified that at least 14 species of sharks and rays reside at Glover’s Reef atoll, at least four of which breed at this site, including the Caribbean reef, nurse and lemon sharks.

Two especially exciting discoveries have resulted from this long-term survey. Researchers learned that the atoll is frequented by two shark species never before recorded in the region. A mysterious shark captured in the 2001 survey proved, after DNA analysis by Dr. Chapman, to be a Galapagos shark, the first record of this species in the Western Caribbean region since 1963. Then in October 2007, the team began to set deep longlines off the entrance to the atoll, in more than 1,000 feet of water. These longlines captured large numbers of adult male and female Cuban night sharks – the first such discovery in Belize. This species is considered overfished in the U.S., so the discovery of a new and apparently healthy population on Glover’s Reef is very significant.

Perhaps this most significant discovery of this survey has been that the catch rate of large predatory sharks has been both robust and stable at Glover’s Reef. This finding prompted us to look deeper into why sharks at this location appear to be flourishing, at a time when many shark populations around the world are collapsing. The answer was revealed when we began tracking sharks at this site.

The Institute is also joining forces with Shark Savers to develop a public-supported ‘Parks for Sharks’ program at Glover’s Reef Marine Reserve that will add a new level of public participation and support to the long-term shark survey. A web site, community, and expeditions will be created in 2009 as part of Parks for Sharks, offering an accessible education experience whereby people can contribute to and develop a relationship with this important conservation project and its shark citizens.

Shark Movements in Relation to MPA Boundaries

Why has the Glover’s Reef MPA been successful for shark conservation? The MPA employs an innovative zoning plan that creates an effective sanctuary for sharks that stay within its very expansive boundaries, as they do much of the time, according to our research. The Reserve consists of a central no-take zone where no fishing of any kind is allowed, nested within a larger zone that covers the whole atoll and prohibits gillnet and longline fishing, the preferred shark-fishing methods in the region. It is the combination of the ban on these two fishing methods and the large size of the MPA that underpin this success.

The Institute’s shark team has methodically captured sharks at the atoll year after year, surgically implanting “acoustic transmitters” to the sharks’ bodies. Each transmitter is uniquely coded, and each shark’s movements are carefully tracked by an array of “receivers” that have been moored around Glover’s Reef. Whenever a shark swims within a 500-meter radius of the receiver, the exact date and time is recorded. The shark team collects the receivers twice a year to download and analyze the data, and generates detailed movement-pattern histories for each shark. This invaluable information provides a thorough sharks-eye view of the reefs each animal frequents, their residency times in the MPA throughout the year, how far they travel beyond the MPA, and the number of days that they leave the fully protected no-take zone of the MPA.

Tagging and tracking work has predominantly focused on two economically-important sharks -- the Caribbean reef shark, Carcharhinus perezi, and the nurse shark, Ginglymostoma cirratum. To date, 47 reef sharks and 25 nurse sharks ranging from newborns to adults have been fitted with transmitters on Glover’s Reef, unwittingly educating scientists while going about their daily routines of swimming and feeding. Through this system of “automated acoustic telemetry,” our scientists have learned that most of these sharks exhibit strong residential behavior that keeps them within the Reserve for extended periods. That means they are benefitting from the MPA’s expansive protective boundaries.

Caribbean reef shark 3290, for example, was tagged within the no-take zone in May 2006. Although this robust adult female never migrated away from Glover’s Reef atoll, she occasionally moved long distances along the reef and outside the no-take zone. If the MPA were not as large as it was, or gillnet fishing was allowed outside of the relatively small no-take zone, this shark and others would have a high probability of being killed. The innovative design of the Glover’s Reef MPA has allowed her and others of her kind to flourish. The Institute’s continuing studies show that the Glover’s Reef MPA is an effective model for MPA design that may be useful to better protect sharks on coral reefs all over the world. It is a win-win situation, permitting local residents to continue using traditional fishing methods within the MPAs boundaries, while prohibiting over a large area the long lines, gillnets and trawls that have decimated sharks in many parts of the world.

Remote Video Survey of Sharks Across the Belize Barrier Reef

Shark fisheries are expanding in Belize, and there is anecdotal evidence of serious declines in shark populations. Our acoustic tracking and longline survey time-series data have shown that robust and stable shark populations still exist in the Glover’s Reef MPA. It is possible that further restricting use of gillnets and longlines across Belize could be an effective strategy for shark conservation across an even larger area.

The Institute’s team is now interested in looking at shark abundance across the entire barrier reef. Unfortunately, longlines and gillnets are not banned in all of Belize’s MPAs, which means that large scale shark fishing is still conducted legally in these areas. We are comparing shark abundance in MPAs where longlines and gillnets are banned, in MPAs where these techniques are legal, and in places that are completely open to all forms of fishing. This information will help the team determine whether prohibiting longlines and gillnets across all 600,000 acres of Belize MPAs would improve regional shark conservation, and will help us to identify potential future sites for MPAs.

The team is using a technique known as “baited remote underwater video” (BRUV) to gather information rapidly from a wide area of the barrier reef. Each BRUV consists of an underwater video camera that is remotely deployed on the seafloor in front of a bait source. The camera films all animals attracted to the bait source for 2 hours, allowing several quantitative measures of shark abundance to be made (e.g. number of sharks observed, time till first shark observed). This technique has been successfully used to study shark abundance on Australia’s Great Barrier Reef, but never before on the Belize Barrier Reef. The technique is robust, yet relatively cost-effective and environmentally-friendly. BRUVs are easy to deploy and highly portable, making it feasible for a small team to sample a large area rapidly. The video shark survey is funded by the Roe Foundation. Stay tuned for remote video of sharks from Belize coming this summer!

More Information:   Research Station on Glovers Reef  |  Shark Savers Site  |  Demian Chapman  |  Ellen Pikitch

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