Tuesday, August 20, 2013

Shark Research in Action: North Sound

Pink sky at night, lemon sharks delight.
Guest Blog
By Annie Anderson and Antonia Ash

The first night’s fishing went down a storm with a record number of sharks caught, a total of 83 juvenile lemon sharks were transported to the tagging boat for processing. Here they were ‘worked up’ - measured, weighed, sampled forDNA and stable isotope, and finally scanned for a PIT tag. At this stage we recorded the PIT ID for recaptures (those with an existing tag), and inserted a new one for those without. Finally we recorded the umbilical scar status of all sharks under 70 cm in length. Did you know that sharks have belly buttons? In the same manner as humans, in utero lemon sharks are connected to their mother with an umbilical cord. We review this scar and if it is still open we know that it is a newborn that was likely born to the nursery in the past few weeks.

Our tagging and net boat teams are made up of staff and volunteers to ensure we have a mixture of experience and heavy lifters. One of our principle investigator’s, Rob, led net boat one. Those who have worked PIT in previous years know this is notoriously our busiest net. Within 5 minutes of setting the net they had already caught their first shark. He was a 63 cm new capture.

Measuring the shark
Each net boat aims to bring the sharks caught straight over to the tagging boat to reduce stress. On the first night of North Sound another of the principle investigators at the lab, Jean-Sebastien, led this boat. The tagging team alongside Jean experienced the most chaos of the night: one tagging boat with the 83 catches. With so much going on, organization and attention to detail was vital at all times, particularly through the 8 to 9 PM rush when 23 sharks were worked up in only 45 minutes.

This of course leads us back to the work of the other two nets who were themselves busy catching more juvenile lemon sharks to add to the nights count. In the end the total from net one was 36, net two fell just under with 32, and net three caught 15, which is a reflective split of what we have come to expect each individual net to catch through the labs 18 years experience of PIT. The second and third night yielded a smaller number of catches in comparison, but the numbers were enough to keep the net boats on their toes.

Sharks have bellybuttons.  I bet you didn't know that.
After a night’s break from gillnetting, the team returned to complete the North Sound part of PIT, another three nights in the same net locations. With a decreasing number of new shark captures the crew spent less time in the water catching sharks and more time on the boats making mad libs, getting to know each other, and counting shooting stars. Not to put too fine a point on it, the PIT crew go away with many awe inspiring memories and none can match the setting which surrounds the net boats at night: complete silence in darkness with the occasional flash of a Q-beam to remind each net boat that the other teams are close by.

Of course when reminiscing upon this peaceful dreamy picture how could we forget the sudden interruption of flashing blue lights, the sound of an echoing siren, and a startling spotlight shone across the astonished faces of net three by a local police officer. As you would imagine a sight to witness in the early hours, but with the get out of jail clause ‘we’re from the sharklab,’ the officer was soon reassured that no suspicious activity was taking place and he was on his way.

Over the six nights of gillnetting in the North Sound the total juvenile lemon shark count for PIT 2013 came to an impressive 120.

The Bimini Biological Field Station Sharklab depends on the efforts of dedicated volunteers to accomplish our research. Since its 1990 inception, the BBFS Sharklab has been host to thousands of volunteers from all over the globe. Annie Anderson blogs at Sharks Need Love.
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