NOTES FROM THE FIELD
Sharks of the shallows
McGill’s Joseph DiBattista
examines the umbillical scar
on a young lemon shark
Amy Jefferies
By JOSEPH
DIBATTISTA
Editor’s note: In an
attempt to combat the brutal
January cold, we’ve decided
to run an installment of our
popular Notes from the Field
series that took place in
sunny Florida last summer.
If you’re a McGill
researcher conducting field
work and would like to file
a Notes from the Field
dispatch, or if you know of
a great potential
correspondent, contact Neale
McDevitt at 514-398-1044 or
at
neale.mcdevitt@mcgill.ca.
June 23, 2007:
We did it, we finally did
it. After months of planning
and shopping, and having
secured both a vessel and
able crew, we are set for
our eight-day genetic
sampling expedition to
Marquesas Key (MK), Fla. MK
is a mangrove-fringed island
in the Florida Keys,
approximately 25 km west of
Key West. It encloses a
shallow seagrass lagoon that
also serves as a nursery
ground for between 75 and
100 juvenile lemon sharks
each year. This marks the
ninth year that Dr. Samuel
Gruber (a retired professor
with the University of Miami
and acting research director
for the expedition) has
returned to the area with
his crew of capable
volunteers in an attempt to
characterize the mating
patterns of lemon sharks. I
have been coming back every
year since 2004.
Looking over the gear, I
am amazed by the sheer
volume of it all: two trucks
filled to capacity with
research tools and personal
items, a 19-foot Carolina
skiff packed with mesh and
iron rebar to build a shark
holding pen, and a 17-foot
inflatable Zodiac jammed
with gillnets (to catch
smaller sharks), fishing
rods (to catch larger
sharks), 80 gallons of fuel,
and a spare 25hp boat
engine. Although it is
inevitable that we’ve
forgotten something, no one
could accuse us of not being
prepared—we have spare items
for our spare items.
We leave the Miami home
of Dr. Gruber early in the
morning, and make the
four-hour drive south to Key
West. As I climb in the 1987
Areostar—a vehicle lacking
in air conditioning and
functioning windows—I notice
our driver has stripped down
to his underwear to beat the
unbearable Florida heat and
humidity. It looks like it’s
going to be one of those
trips.
June 24, 2007:
This morning we sailed west
for MK aboard our 40-foot
chartered vessel Off the
Porch with a crew of nine
and our two smaller research
skiffs in tow. Upon arrival
we set about marking the
entry channel into the
lagoon with reflective
floats and cannonball
weights (for navigation at
night), and building the pen
where sharks would be held
for the remainder of the
week. Once finished, we
divide into crews and
prepare the gear for our
first night of fishing.
Although logistically a bit
more taxing, night is the
best time to catch juvenile
sharks because they are more
active and less likely to
spot and avoid the
monofilament gillnets. One
crew will fish for smaller
sharks from 6 pm to 6 am
and, while they sleep, the
day crew will clean gear,
prepare meals, and fish for
larger (subadult) sharks on
the flats surrounding the
lagoon. With space enough
for only five to sleep at a
time, quarters are cramped.
By the end of the week no
one seems to mind, or at
least they are too exhausted
to complain.
We leave the main vessel
at 5:30 p.m. One boat sets
the net and checks it every
15 minutes; the other boat
anchors near the holding pen
in preparation for tagging.
The waiting game begins. The
stillness is incredible.
Free of ambient city lights,
stars pepper the sky. Every
so often a satellite careens
across the brilliant
landscape. Almost six hours
later the radio springs to
life, “Tagging boat, tagging
boat, come back to net
boat.” We got one! The net
boat drops off the shark; it
is clearly a newborn, as
evidenced by the open
umbilical scar on its
ventral side. Our crew goes
about measuring the shark,
inserting a passive
integrated transponder (PIT)
tag for mark-recapture
purposes, checking for signs
of infection or capture
stress, taking a small piece
of fin tissue for later
genetic analysis, and
finally weighing the animal
before placing it in the
holding pen. Unfortunately
this is the only shark we
caught tonight—disappointing
given that we generally
catch between 10 and 15 on
the first night.
June 25-27, 2007:
More fishing, more fishing,
more fishing. No sharks, no
sharks, no sharks. Where
have they all gone? We catch
only seven more juveniles
over this period.
June 28, 2007:
Tonight we decide to set our
nets in a different
location. En route to the
predetermined spot, we
notice smoke billowing out
of the mangrove trees. We
sail a bit closer to shore
and spot a large group of
people waving white towels,
asking for help— Cuban
refugees whose raft has run
aground. We notify the Coast
Guard who promptly arrive
and bring them to safety. We
are relieved to hear that
the Cubans will be brought
to Miami, debriefed and
allowed to stay under
refugee status. It is hard
to focus on research after
this experience, but we
forge ahead. We catch and
tag two more sharks.
The
U.S. Coast Guard rescues 19
Cuban refugees whose raft
had run aground
Amy Jefferies
June 30, 2007:
I am awoken by
panic-stricken screams. “Doc
has been bit, Doc has been
bit.” Dr. Gruber has been
bitten badly on the hand by
a subadult lemon shark while
trying to free the hook from
its mouth. It is only the
second time in his 40-year
research career that he has
been bitten, a formidable
track record. It takes
nearly two minutes to free
his hand from the shark’s
jaws using a boat paddle as
a pry bar. The razor sharp
teeth had cut him to the
bone. Luckily, Dr. Gruber
kept his composure during
the ordeal and remained very
still, as any sudden
movements would have
resulted in his hand being
ripped to shreds.
I notice him sitting on
the bench in the galley,
clearly in pain now with his
left hand immersed in a
large bowl of hydrogen
peroxide. The decision was
promptly made that the trip
would end one day early and
Dr. Gruber would be brought
to Key West hospital to
receive medical attention—a
change of plans to which he
only begrudgingly agreed.
Dr.
Samuel Gruber after being
bitten by a subadult lemon
shark
Amy Jefferies
July 1, 2007:
Dr. Gruber gets stitches but
his hand will be OK—he’ll be
left with just a few
puncture scars to mark the
ordeal. After arriving back
in Miami and unloading our
gear we reflect on the
research trip during which
we only caught 17 lemon
sharks. Our lowest catch
from previous years was 34.
The most likely explanation
for the low number was that
our timing was off. We had
arrived almost a month
earlier than previous years
to avoid hurricanes, which
have hampered our work in
the past. But it looks like
we preceded the arrival of
most pregnant females
entering the nursery lagoon
to give birth. We are not
discouraged by the fruits of
our labour. Each sample we
obtained is critical, and
will help answer key
questions about the mating
system of this species.
Joseph
DiBattista is a PhD
candidate in the Department
of Biology under the
supervision of Dr Andrew
Hendry. He is part of a
collaborative research
project on mating systems
and evolution of lemon shark
populations in the Atlantic
involving McGill University,
the Field Museum in Chicago
(www.fieldmuseum.org),
and the Bimini Biological
Field Station in the Bahamas
(www.miami.edu/sharklab).
This project is partly
funded by the Natural
Sciences and Engineering
Research Council of Canada,
and the National Science
Foundation, among others.
