New research suggests that expanding marine protected areas into U.S. federal waters would safeguard 100 percent of the core home range of bull, great hammerhead and tiger sharks living in the northwestern Atlantic Ocean.
Large sharks occupy the top of the ocean food chain, and the loss of too many of them through fishing would have devastating impacts on the marine environment. Therefore, scientists are interested in learning more about how to protect the iconic animals.
One way in which sharks are protected is through the implementation of marine protected areas (MPAs). However, there are different types - national park, state and federal waters - that all warrant their own regulations.
In the latest study from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, researchers tagged 86 bull, great hammerhead and tiger sharks in waters off south Florida and the northern Bahamas. The goal, they say, was to learn more about the animals' core home range and how they may benefit from spatial protection, such as MPAs.
Core habitat use areas (CHUAs) are defined as the areas in which the sharks spend the majority of their time. Every time a tagged surfaced, location data was collected from their trackers. Researchers monitored this data in relation to areas where fishing is prohibited or exclusive economic zones (EEZs) in the U.S. and the Bahamas, which offer full protection for the animals.
"There are concerns that spatial protections may not benefit large sharks since they are highly mobile and likely to regularly move in and out of MPAs," said study co-author Neil Hammerschlag, a research assistant professor at the UM Rosenstiel Marine School and UM Abess Center for Ecosystem Science and Policy. "While it's not feasible to protect highly mobile species wherever they go, our findings suggest that significant conservation benefits can be achieved if they are protected in areas where they spend the majority of their time, such as their core habitat use areas."
Data collected by the researchers revealed that none of the tracked bull sharks' regional CHUAs are located in areas that are fully protected from fishing. Furthermore, of the great hammerhead and tiger sharks tracked, only 18 percent and 35 percent of their CHUAs were currently protected, respectively.
However, researchers also found that the majority of the CHUAs utilized by all three shark species were within the U.S. EEZ. In 2012, Florida enforced new regulations, prohibiting the harvest or capture of four shark species, including tiger and great hammerhead sharks, in state waters.
"Our results will help enable policy makers to make more informed decisions when developing conservation plans for these species, particularly when considering a place-based management approach," added lead author Fiona Graham.
Previous studies have found that the waters of Florida and the Bahamas are important breeding and feeding grounds for sharks. The species tagged in the most recent work are considered near threatened or endangered. In fact, populations of hammerhead sharks in the northwest Atlantic and other areas have declined more than 80 percent over the last two decades.
"This is of particular importance for hammerheads sharks since they are experiencing the greatest declines in the region and are of high conservation concern," Hammerschlag explained. "However, this species is susceptible to death from capture stress, so effective conservation strategies would also need to prevent great hammerheads from capture in the first place."
Their findings were recently published in the journal Diversity and Distributions.