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A
pressure catheter is adhered
inside a PVC pipe and connected to a computer. The PVC
pipe has bait adhered to the outside surface to encourage the nurse sharks to
use
suction
to
remove
it.
Left: Alpa demonstrates the catheter
set-up, while Dayv baits in sharks and Lisa readies the polecam.
Right: Phil at one of our computers,
which is actually a Yokogawa oscilloscope. The tarp protects our equipment
from saltwater. |
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The
PVC pipe is tethered to the dock so that the sharks cannot swim off
with it. If they cannot suck off the prey, the sharks will
sometimes bite down on the pipe and try to swim under the dock with
it, as shown in the photo on the right. |
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There
are other elasmobranchs at this site as well, including lemon sharks,
bull sharks, and a large
southern stingray. Since we bait the water to attract the nurse sharks,
the lemon sharks tend to come to feed as well and bite our equipment. We
also had to look out for three goliath grouper, or jewfish. They easily
could pull one of us into the water if they got hold of the pole-cam, which was
not tethered to the dock.
Left: We've had to pull out the pole-cam
before as a lemon shark tried to bite it. There is also a nurse shark in
the right corner of the photo.
Right: Two goliath grouper have found
some of our bait. |
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| The final stage of this
experiment was to measure external and internal suction pressure while
simultaneously taking measurements from electromyography (EMGs).
This part of the experiment was done at Mote Marine Lab. After anesthetizing
this captive nurse shark, we implanted wires into some of the cranial
musculature (which are visible just above the pectoral fin) and inserted
a pressure cannula into the buccopharyngeal cavity via the gill spetum
(catheter is visible above the gill slits). |
As
the animal recovers from anesthesia, we set up our high speed video
equipment to link kinematics with the EMG and suction data.
Left: The nurse shark is in the tank
in the back of the room. Mike monitors the shark to make sure that
he doesn't pull out any of the leads or the catheder.
Right: Dayv replays high-speed video
of a suction event, while Dan looks over the suction pressure data. |
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| External and internal pressure profiles for a suction capture event. |
| All photos are © Philip Motta |
