TW_06.14.10_Edition.pdf - St. John Tradewinds News

St. John Bays Ideal for Shark Nurseries, Important
To Sustaining Shark Populations, NOAA Discovers
By Andrea Milam
St. John Tradewinds
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
St. John Tradewinds News Photo by Bryan DeAngelis
Student assistant Ian Bouyoucos examines a blacktip
shark as part of the National Oceanic and Atmospheric
Administration’s Virgin Islands shark research project.
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.”
St. John Tradewinds, June 14-20, 2010 5