Yup.. It’s been a while so grab a coffee this is going to be a long one! The below blog was written by myself and Antonia Ash, June 2013.
From South Africa to Brazil, from the US to the UK over to Belgium and finally France, 29 people from all over the world came together for the 19th BBFSF annual juvenile lemon shark population census in Bimini, Bahamas. Despite the blood sucking mosquitos and lightening illuminating the skies above, the crew rallied together to make PIT 2013 the year to remember.
For the past 18 years the Sharklab has monitored the juvenile lemon shark population in Bimini assessing survival, growth and mating characteristics of the lemon sharks in two mangrove-fringed nursery areas: North Sound and Sharkland. PIT (Passive Integrated Transponder) is a 12-night project which takes place annually in the month of June and is a little rice-grain sized microchip with a unique code which is inserted under the skin of the lemon shark. This chip represents both the literal process involved in tagging each shark as well as providing us with the name for the longest running research project the Sharklab conducts.
Every night between 5 and 7pm three net boat teams and one tagging boat team leave the Sharklab and head towards their allocated net locations in either North Sound or Sharkland. On arrival it is the tagging boats responsibility to ensure all net boats set at the same time and from that point on they must all check their nets every 15 minutes over a 12-hour period from dusk till dawn. On finding a shark in the net the team immediately remove it, record the time and location of capture and radio the information through to the tagging boat before transporting the shark for a more detailed ‘work up’. The information recorded at this stage is crucial for past and future data comparisons, for example when they are re-captured we can determine how much they’ve grown, who their siblings are (through DNA), their weight fluctuations and movements from initial capture locations.
After the long and tiring12-hour cycle and as the sun rises the net boats haul their lines and all head back to the lab for a hearty breakfast prepared by the hard working home crew. All equipment is cleaned and the team then head to bed for a 6-8 hour nap before they must wake to start the whole process again.
The first nights 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, DNA and stable isotope taken and finally scanned for a PIT tag. At this stage we recorded the PIT ID for recaptures (those with an existing tag), and for those without one was inserted. Finally we recorded the umbilical scar status of all sharks <70cm. In the same manner as humans, juvenile 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 with new faces. One of our Principle Investigator’s Rob led net boat one and for those who have worked through PIT in previous years will know this is
notoriously our busiest net: within the first 5 minutes after setting they had already caught their first shark and he was a 63cm new capture.
Each net boat aims to bring the sharks caught straight over to the tagging boat to reduce stress and on the first night of North Sound this boat was led by another of the Principle Investigators at the lab, Jean-Sebastien. The tagging team alongside Jean certainly experienced the infamous chaos of the night one tagging boat with the 83 catches; high organization and attention to detail was vital at all times, particularly through the 8pm-9pm rush when 23 sharks were worked up in 45mins.
Me taking a girth measurement
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.
After a nights 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 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 finer 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 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.
PLEASE FOLLOW THE SHARKLAB ON TWITTER: www.twitter.com/BiminiSharkLab
As the crews left for night one of Sharkland the conditions were ideal for setting the gillnets and the competition for the straightest net was on.
However as the saying, ‘the calm before the storm’ goes, within a few hours the crew found themselves snuggled up hiding under transport boxes with bolts of lightening landing within a stones throw. Despite the relentless rain, 35 sharks were still captured and the crews soldiered through the conditions ensuring they met their 15 minute check window. Unfortunately with conditions deteriorating by the minute the decision was made to haul all lines four hours ahead of schedule, with the time to be made up over the coming nights.
Antonia and Lindsay snuggled under a transport box!
As the nights spent in Sharkland went on the count was lower than in previous years with night two totaling 13 and night three falling just under with 12. Despite the low shark count the PIT crew still had some interesting captures with net three finding the largest shark caught in their gillnet during the whole of PIT 2013, measuring 116cm. Net one also witnessed a returnee caught only the week before in North Sound which had escaped from the behavioral holding pens. Amongst all the shark action and the delirium of the night, in between checks net one, led by new assistant manager David, found themselves stalking what they believed to be a four meter sawfish which in the bright lights of the Q beam transformed into a lonely nurse shark in search of a mate. In an attempt to rescue the team from the nights delirium the annual fancy dress food run arrived to a PIT crew of confused faces as they witnessed those on home duty parading themselves round the boat in extremely minimal cowgirl outfits.
In the final three nights of Sharkland the total count for night four was 17, night five slightly lower with 13 and the final night tapered off with a low of 5; this brought the total count in Sharkland to 95 captures.
PIT 2013 has been a strenuous but rewarding 12 nights for all involved – a special experience for all to take away.