New shark research targets a nearly endangered species

Date:
September 15, 2020
Source:
Nova Southeastern University
Summary:
They are some of the most iconic and unique-looking creatures in
our oceans. While some may think they look a bit 'odd,' one thing
researchers agree on is that little is known about hammerhead
sharks. Thanks to a team of researchers, that's all changing.



FULL STORY ==========================================================================
They are some of the most iconic and unique-looking creatures in our
oceans.

While some may think they look a bit "odd," one thing researchers agree
on is that little is known about hammerhead sharks. Many of the 10
hammerhead shark species are severely overfished worldwide for their
fins and in need of urgent protection to prevent their extinction.


==========================================================================
To learn more about a declining hammerhead species that is data poor
but in need of conservation efforts, a team of researchers from Nova Southeastern University's (NSU) Save Our Seas Foundation Shark Research
Center (SOSF SRC) and Guy Harvey Research Institute (GHRI), Fisher Finder Adventures, the University of Rhode Island and University of Oxford
(UK), embarked on a study to determine the migration patterns of smooth hammerhead sharks (Sphyrna zygaena) in the western Atlantic Ocean. This
shark, which can grow up to 14- feet (400 cm), remains one of the least understood of the large hammerhead species because of the difficulty in reliably finding smooth hammerheads to allow scientific study.

To learn about smooth hammerhead behavior, the research team satellite
tagged juvenile hammerhead sharks off the US Mid-Atlantic coast and
then tracked the sharks for up to 15 months. The sharks were fitted with fin-mounted satellite tags that reported the sharks' movements in near
real time via a satellite link to the researchers.

"Getting long-term tracks was instrumental in identifying not only
clear seasonal travel patterns, but importantly, also the times and
areas where the sharks were resident in between their migrations,"
said Ryan Logan, Ph.D.

student at NSU's GHRI and SOSF SRC, and first author of the newly
published research. "This study provides the first high resolution,
long term view of the movement behaviors and habitats used by smooth
hammerhead sharks -- key information for targeting specific areas and
times for management action to help build back this depleted species."
The researchers found that the sharks acted like snowbirds, migrating
between two seasonally resident areas -- in coastal waters off New York
in the Summer and off North Carolina in the Winter. Their residency
times in these two locations coincided with two environmental factors:
warmer surface water temperatures and areas with high productivity -- indicative of food rich areas.

"The high resolution movements data showed these focused wintering and summering habitats off North Carolina and New York, respectively, to
be prime ocean "real estate" for these sharks and therefore important
areas to protect for the survival of these near endangered animals,"
said Mahmood Shivji, Ph.D., director of NSU's GHRI and SOSF SRC, who
oversaw the study.

Identifying such areas of high residency provides targets for designation
as "Essential Fish Habitat" -- an official title established by the US Government, which if formally adopted can subsequently be subject to
special limitations on fishing or development to protect such declining species.

The tracking data also revealed a second target for conservation. The hammerheads spent a lot of resident time in the winter in a management
zone known as the Mid-Atlantic Shark Area (MASA) -- a zone already
federally closed for seven-months per year (January 1 to July 31)
to commercial bottom longline fishing to protect another endangered
species, the dusky shark. However, the tracking data showed that the
smooth hammerheads arrived in the MASA earlier in December, while this
zone is still open to fishing.

"Extending the closure of the MASA zone by just one month, starting on
December 1 each year, could reduce the fishing mortality of juvenile
smooth hammerheads even more," said Shivji. "It's particularly gratifying
to see such basic research not only improving our understanding of animal behavior in nature but also illuminating pathways for recovery of species
and populations that have been overexploited so we can try and get back
to a balanced ocean ecosystem." The tracks of the smooth hammerheads
(and other shark species) can be found here: http://www.ghritracking.org.


========================================================================== Story Source: Materials provided by Nova_Southeastern_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ryan K. Logan, Jeremy J. Vaudo, Lara L. Sousa, Mark Sampson,
Bradley M.

Wetherbee, Mahmood S. Shivji. Seasonal Movements and Habitat Use
of Juvenile Smooth Hammerhead Sharks in the Western North Atlantic
Ocean and Significance for Management. Frontiers in Marine Science,
2020; 7 DOI: 10.3389/fmars.2020.566364 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200915105936.htm

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