URI researchers use tracking data to better inform mako shark management
University of Rhode Island shark
expert Brad Wetherbee has been tagging mako sharks up and down the East Coast
for nearly 20 years and tracking their migratory movements around the North
Atlantic. That data is now proving useful in a study aimed at improving the
management of this imperiled species.
Mako sharks are among the fastest
fish in the ocean, and they travel great distances throughout the year, seldom
spending long in the waters of any one nation. That’s why, according to
Wetherbee, managing the species is so difficult. No nation wants to take
responsibility for a species that is already considered globally overfished.
Using Wetherbee’s tracking data,
which was collected in collaboration with the Guy Harvey Research Institute,
graduate student Maria Manz will soon be able to point the finger at which
nation should take charge.
By analyzing 60,000 data points
indicating the locations of tagged mako sharks, Manz will be able to identify
in which jurisdictional waters the sharks spend most of their time and at what
time of year. She can even break down that data by the sex of the sharks, which
could be vital since females are more important to the health of the species
than males.
“I’m looking at the relative proportion of detections per jurisdictional boundary to tell us what country has the most detections in their waters,” said Manz, a native of Titusville, New Jersey, who earned a bachelor’s degree from Moravian College.
“The goal
is to identify which country should allocate their resources to mako
management, or, if most of their movements are in international waters, if an
international governing body should come together to come up with a uniform
law.”
Manz is also using the data points
to identify what she calls “highly utilized areas” along the East Coast –
regions where mako sharks spend considerable amounts of time – and comparing
those areas to conservation zones like marine protected areas and sites
designated essential fish habitat.
“We want to see how they align,” she
said. “If areas highly utilized by the sharks are outside these marine
protected areas, then that isn’t great. If they don’t align, you might question
whether that protected area can protect mako sharks.”
In addition, Manz is assessing how
mako shark movements intersect with recreational fishing areas and planned
offshore wind development regions along the East Coast.
“The theory is that wind farms will
create artificial reefs that will be attractive to sharks, just like oil rigs
do in the Gulf of Mexico,” Manz said. “It’s been hypothesized that these new
reefs could become highly productive areas that could affect the migratory
patterns of the sharks.”
Finally, Manz is using the tracking data to estimate the size of the sharks that visit particular areas to determine the success of a 2019 rule about the minimum size limit of mako sharks that are allowed to be kept by recreational fishermen.
The National
Oceanic and Atmospheric Administration rule increased the length of mako sharks
allowed to be kept to 71 inches for male sharks and to 83 inches for females.
The objective is to determine whether the change in the size of sharks that can
be retained has affected their distribution and abundance.
“All of this is designed to provide
useful information about things that people don’t have a good idea of,” Manz
said. “We have this great data set for providing information to stakeholders
and fishery managers, but no one has looked at it like this before. Now they’ll
be able to use this information to base decisions on and to decide what other
studies need to be done.”
To view the tracks of some of the
tagged mako sharks, visit www.ghritracking.org.