Sharkland
Sharkland with net and holding pen locations |
June 12, 2009
Sharkland Start - Vertical Longline
text by Alex Innes, New Volunteer
A large tiger shark along the Proline
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After the completion of our PIT tagging in the North Sound, we had a few days to get ready for Sharkland. During one of these days, we got a chance to go out and set a vertical longline. The line has 15 hooks, with about 75 feet between them, arranged on the bottom of a line 1200 feet long. This line is placed in water 700 feet deep on the west side of Bimini.
In the vertical longlines I have experienced in the past, the shark or sharks have traditionally been on the bottom couple of hooks and this time was no different. After a good bit of manual hauling by Matt, Bryan, Joy, Joey, and Andy, a shark appeared from the depths.
The crew observes a 12 foot tiger shark
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The female tiger shark had heavily wrapped its tail up in all the gear at the bottom of the line, including the cinder blocks and chum bag. Bryan struggled to free the shark’s tail from the mess, and after five minutes with wire cutters his job was completed. The shark was measured and had a total length of 361 centimeters (approx. 12 feet). After this a Casey tag was attached. At this point we were all allowed to hop in the water and swim around with it while it was secured to the boat. I was fortunate enough to hold it with my left hand hanging onto its dorsal fin and my right hand on its right pectoral fin. When I went to do this I was reminded immediately of how sharp, not rough, shark skin really is. The little lemon sharks in the North Sound have skin that is comparable to sand paper, but the skin on this big tiger scraped up my arm and side. Shortly after I held the shark Bryan cut the hook, the tail rope was removed, and she swam away nicely.
Joy gets a close look at the large tiger shark
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New volunteers and old staff alike get excited for a large tiger. Besides Alex, many of the crew got to touch and have their picture taken with the large tiger. The sheer size and girth of this fish was impressive. We would have loved to spend more time with this amazing animal, but because it had been badly wrapped in the lines we had to quickly do a workup, take a few pictures and try to release the shark to limit the amount of stress it endures. Bryan and Joey gave it a gentle push and it slowly glided away with gentle flicks of its tail. The tiger was big and bulky, but was graceful and elegant in its movements as it slowly returned back to the depths. We all watched this giant disappear into the blue with admiration. Spirits are running high, and the team is all set to face the first night of Sharkland head-on. Tomorrow is the "Main Event" - the busiest and craziest night during the entire PIT project. Excitement is high and the crew is ready - game on!
June 13, 2009
Sharkland Fishing - Night 1
"The MAIN EVENT"
text by Christina Comfort, Volunteer
The boats head out to begin fishing in Sharkland
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Commencing Sharkland Fishing! Tonight will be the busiest night of PIT, and still riding high on adrenaline from the massive tiger shark on the vertical line, the team is more than ready for the challenge. To handle the huge catch of juvenile lemon sharks tonight, most of the team will be out in the field, leaving only five people to keep things running back at the lab. The away team rested up during the afternoon and headed out a couple hours before low tide to set the nets in the evening. The tagging boat and Net 3 (the busiest net) both had extra-large crews of five people apiece, and everyone was prepared to be up and running all night. I was a crew member on Net 3, and I went into the evening feeling a bit nervous since I'd only gotten one lemon shark out of a net before tonight and I was surrounded by PIT veterans. However, just about 10 minutes after we set, things got busy enough that we were all taking sharks out of the net pretty consistently. The Net 3 catch was constant but not crazy - at least in the early evening.
A Net 3 walk check at sunset
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Just before dinner, the Net 3 Mad Rush began. Up until then, we were getting one shark at a time in the nets, but suddenly four to six sharks were hitting the net at once. Kat, Joy, and I were all getting sharks out of the net. Matt was keeping an eye on the sharks in our small pen. Captain Joey was driving the boat, trying to run as many sharks as possible over to the tagging crew at the main pen. Everyone worked quickly and calmly, getting all the sharks out ASAP. Eventually, we managed to pick up our (delicious) enchilada dinner from the home crew, but there was no time for food yet! Joy went home at dinner, but Hollie joined our Net 3 crew so we still had enough people to keep things under control. Around 2:00 am, the rush slowed down to a more manageable pace, and we were finally able to grab a well-earned bite to eat and sip (or chug) a coffee. During all this craziness on Net 3, Nets 1 and 2 were still consistently catching sharks as well, so the night was even busier for the tagging crew, who worked non-stop for all 12 hours. We hit a second rush in the early morning hours - at one point, Hollie, Kat, and I each had a shark in hand and more were still in the net!
Kat frees a lemon from the net
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By the time the night was over, our net alone had caught 58 sharks. The total for the evening rolled in at 94 juvenile lemons, including 52 neonates. When Kristine called for the boats to haul their nets in the morning, we couldn't believe it - the night had absolutely flown by, and we were still busy, with about 6 sharks left in our small pen waiting to go to the main pen. After the haul, some of the sharks in our pen needed a little extra attention, since they were exhibiting a behavior called spiraling. Spiraling can occur when sharks get stressed, and they start to swim in a spinning, disoriented manner. When sharks start to spiral, we keep an eye on them, try to keep them right side up, and make sure they are breathing well. If they aren't breathing as well as they should, holding the shark right side up and walking it around in the water can also help. After two hours and a beautiful sunrise, most of our sharks were in the main pen and most of the crew headed home, leaving Kat and Matt to look after a couple of stragglers. The crew was pretty spent after catching and working up nearly 100 sharks, so after a great scrambled egg breakfast, we all passed out and tried to summon up some more energy for night two!
June 14, 2009
Sharkland Fishing - Night 2
The Sharkland main pen
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The first night of Sharkland lived up to its billing and put the team to the test. We caught more sharks last night than in the entire 6 days in the North Sound. Additionally, we had some sharks come out of the nets in poor condition. They exhibited some spiraling behavior, and a lot of extra attention and work needed to be put in by the team to get through the night. Despite the extra efforts, we unfortunately had several mortalities. While inevitable, it is always disheartening to see a dead shark. Our methods have been refined over the years to minimize the impact our sampling has on the sharks. Everyone here is passionate about the juvenile lemons, and we put great care into working with them so that they can happily swim away when we are done. The long night and the dead sharks have taken quite a bit out of the team. After grabbing some sleep, the team steels its resolve and gets ready to head back out into the trenches.
Lemons cruise in the main pen
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The team fanned out into their locations in the lagoon and set to the task at hand. Night two should be less hectic and crazy than night 1. Instead of coming in large bunches, sharks were hitting the nets in much more manageable ones and twos. Each net could be worked through the night, check by check. As the tide rose, the nets started to bring sharks over to the tagging boat. While there were still a few weak sharks, overall they seemed to be stronger than the previous night as they were removed from the nets. The team drew a large collective sigh of relief. The more leisurely pace and assuaging of our fears over the condition of the sharks did wonders for team morale. Pretty soon the radios were live with chatter as the teams played games and traded trivia to pass the night's wee hours.
Putting a gillnet capturee in the main pen
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All three nets had some action tonight, and after 12 long hours the team was able to amass 21 sharks. This total includes 6 neonates and 9 recaptures (3 of which were from the recent fishing in the North Sound). We had two sharks that
were somewhat weak coming out of the nets but we continuously monitored them, and by dawn they were happily zipping around the main pen. All the sharks made it through the night, and the team was able to haul the nets and head home with smiles on their faces. With the addition of these 21 sharks, the current tally for Sharkland stands at a very respectable 115. The majority of sharks have been caught, but since this part of the lagoon borders the maze of channels that extend back through the mangroves of east Bimini - there are many places the little sharks can still be hiding. The crew could still get another 30-40 sharks over the course of the next week. We will see how many wander out of the channels into the main lagoon and our waiting nets.
June 15, 2009
Sharkland Fishing - Night 3
The Adventure of the Super Taggers!
Starring the Grand Empress of Brevirostria, the DNA Countessa,
Arch Duchess Hotpants, and Maharaja Sookie
text by Kiki Vinita, Volunteer
Placing alemon in pen post-workup
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Our heroes embarked on their third night of the epic PIT 2009 census in the area known to civilians as Sharkland. The task of collecting these fishy fiends (lemon sharks to be exact) has fallen to the mighty shark wrangling inhabitants of the Bimini Biological Field Station, who will use all their exceptional skill to capture these cunning creatures of the deep (or not so deep as the case may be with the crafty Negaprion brevirostris) for the good of their species.
The night started with our caped crusaders making a check of the current detainees housed in the main pen and ensuring that all the wranglers were in position. Nets were set, vessels were anchored, sharks swam lazily about their pens awaiting their brethren. After all was set the Super Taggers, along with their collective photography sidekick Matt, sprang into action as nets began to capture their targets. The sharks were large and small, feisty and docile, but all yielded to the mighty Taggers will. They were measured, tagged, weighed, and released within minutes of their arrival. Like lightning the Taggers went, with trusty Matt documenting their every move. From data compiling to intense pen maneuvers, never before had these sharks been handled with such grace and skill. Little did those little fishes know our heroes had trained their whole lives for these moments.
Juvenile lemon shark portrait
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In lulls between extreme shark tagging operations, our heroes looked to the sky to contemplate the vast mysteries of the universe. Amid intermittent bursts of light from shooting stars and meteors, the Taggers boosted morale on the net boats with sweet refrains of that most universal of all mediums, music. Aside from sharks, all across the lagoon the toiling Taggers and wranglers awaited one thing...food. Just as that essential substance was to arrive from the few admirable souls who stayed to man the lab, tragedy struck.
The sky is so clear tonight, commented the Grand Empress to her comrades. As the other Taggers (and Matt) were about to agree, the rising moon and twinkling stars were blotted out by ominous clouds. The Taggers thought it was nothing more than a passing haze, and continued about their business and received a visitor in the form of one Kennedy the Kiwi, a traveling chronicler of mangroves. Yet the clouds did not dissipate as they had hoped. In fact, they began to thicken! A race against time began. What would arrive first...the glorious burritos? Or doom from above? All waited with baited breath for word that the food boat was approaching their location. Then the droplets began, softly at first, forcing everyone to break out rain gear and stow away their capes. Then the down pour began, and the Taggers sought shelter beneath whatever transport tub they could lay hands on. All hope seemed to be lost...
A lemon going into the trough
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Then, out of the gloom came the wonderful sound of a boat engine! The Taggers emerged to flag down their saviors and collect their food stuffs. As if by some magic possessed by those of the food run, the rain ceased and the food boat glided effortlessly into place at the bow. Not wishing to tempt fate too much, Sean and Amanda, those two brave souls who had battled the elements sans rain coats to deliver supplies, made their food drop and departed, taking sidekick Matt and Kennedy the Kiwi back to warmth and shelter at the lab. It was well that they had, for moments after they left the cursed rain returned with a vengeance, causing our heroes to once again take refuge beneath plastic boxy shelters. The black lagoon and all within it seemed doomed a long soggy night, and even the beloved food did little to lift the spirits of the wranglers as they came to collect their prizes. Just as all were about to give up home, fortune smiled upon them. Like a bird to its nest, the rain returned to whence it had come. Joy filled their hearts as the Taggers appeared from beneath their cover to continue their quest of tagging the whole neonate population of Sharkland. Thus, they continued until the pink dawn broke across the lagoon. They rode their trusty aquatic steed home in triumph with 16 new sharks placed safely in temporary captivity, knowing they would live to tag another day... (Cue the Heroic Montage Music)
Yep, thats exactly how it went down...
June 16, 2009
Sharkland Fishing - Rest Day
A shark undergoes transmitter surgery
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Today we get a night off from fishing to catch up on repairing gillnets and maybe get a little extra sleep. This also lets the environment up in the lagoon get a break from our intrusion and gives an extra night for the juvenile sharks to come out of the mangrove channels to patrol the lagoon where our nets are placed. As usual, the rest day includes a full schedule of activities. The main activity of the day besides net repair will be to complete transmitter surgeries on two juvenile lemons from the North Sound for Kristine's research. Bryan will complete the first one to demonstrate, and then Kristine will be doing her first shark surgery. She will get lots of practice over the next few years, as she will place transmitters in many sharks for her project. Bryan has done many of these surgeries and will pass on all the little tips he has discovered over the years.
Volunteers observe a transmitter surgery
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Bryan and Kristine decide to let all the volunteers watch the surgeries. Its a small reward for all their hard work to date and a welcome break from sewing gillnets. Everyone gathers in the pen and the first shark is captured. The shark is flipped upside-down
until it falls into tonic immobility. This is basically a phenomenon where sharks go into a trance or sleep-like state as their senses
are overloaded from being in an inverted position. We use tonic immobility to our advantage because it allows us to effectively knock the shark out to allow for easy surgery without the risks of anaesthetizing the animal. The sugery consists of making a small incision in the shark, implanting an acoustic transmitter into the body cavity, and then closing the wound with biodegradable sutures. Bryan points out each step as he smoothly moves through the surgery. Next up is Kristine. She definitely looks nervous as she moves through the surgery. Her surgery takes a bit longer than Bryan's but is equally successful. The lemon shark is flipped back to its normal position and instantly wakes up from tonic. A gentle push, and it is serenely swimming with its cohorts in the holding pen. Kristine breathes a sigh of relief and breaks into a big smile. Everyone congratulates her on excellent performance of her first transmitter surgery. We will hold the sharks in the pen to monitor the healing of the incisions, and when they are fully closed the sharks will be released back into the lagoon. The acoustic tags will be detected by both passive listening stations in the lagoon and by teams maunally tracking them with hydrophones. Another small challenge has been taken in stride, and the crew is moving into the "home stretch" firing on all cylinders. The last three nights of Sharkland are coming up and the team is ready to go out and finish strong.
June 17, 2009
Sharkland Fishing - Night 4
text by Stephen Heck, New Volunteer
Setting a gillnet from a skiff
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After a nap disrupted by a power outage and the resultant heat, the away team woke up for the final three nights of tagging in Sharkland. An early set time and an expectedly lower frequency of juvenile lemon shark captures enabled Diego, Kristine, Matt, and myself to spend time feeding the juvenile lemon sharks in the pen in the later hours of the evening, cameras in tow. The first capture of the evening of 21 total sharks came soon after arriving at the pen with enough light for Matt to take some candid shots of the workup.
Soon after setting the nets the radio began its nightly engagement with talk of sharks and nonsense that tended to lean towards the latter in the early hours of the morning.
Steve shows off a shark
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The stellar display of oranges, reds, pinks, and purples as the sun dropped below the west side of North Bimini was augmented by the first few juvenile lemon sharks of the night. Unfortunately, in the wake of the sunset we got a couple disoriented, spiraling sharks. This behavior is indicative of a highly stressed individual that may need help before the night is seen through. While Kristine and I stayed on the boat to tag, measure, and release sharks delivered to us by the three net boats, Diego spent many hours of darkness snorkeling the main pen to monitor the status of the sharks that seemed to not be doing so well. Diego’s efforts paid off and by the following morning most of the sharks that we had been concerned about were healthy, indiscernible from the mass of 150+ lemon sharks circling the pen.
The dinner crew rendezvoused with Jim relatively early in the evening because low tide was too close to the usual midnight run. Chili over rice really hit the spot and sustained us through the twelve hours out on the water.
Throughout the night lightning shows from afar provided aesthetic entertainment while the sky above remained clear enough to see satellites and shooting stars. Eventually as the storm moved over us, lightning and rain drove us from the metal rebar to take cover in the mangroves with Emily, Hollie, and Marissa near Net 2. Our arrival in the mangroves marked the end of the stint of harsh weather and we soon resumed our place between the pens. The weather held off for the rest of the night, and visits to the tagging boat preempted by shark captures and dance parties continued throughout the night.
Checking the net at sunset
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In the early hours of the morning Amanda, Joey, and Joris, on Net 3, surprised us with a green sea turtle. Jim, Christina, and Kristyn joined us between checks from Net 1 to play with it. Although all of us were ecstatic about seeing him up close, his thoughts seemed to be focused on getting back to the water. Diego showed me that you can distinguish a male from a female by the indent on the underside of the chest of the males and the one that Joris and Kristen found was indeed a male. After some photographs Diego and I swam with him for a little while under the warm water.
The night went by exceedingly fast and with surprisingly no sleep at all, especially on the tagging boat where constant checks on the sharks in the pen, periodic workups, and conversation consumed the hours spent between the rebar and pen mesh. The total count for the night was 21 sharks, bringing the grand total for Sharkland up to 152 individuals and making 2009 a very productive year for shark catches.
June 18, 2009
Sharkland Fishing - Night 5
Dropping a shark into the holding pen
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With our total catch already over 150 sharks, we ventured out again into the lagoon to try and catch the last few sharks that have managed to elude our nets.
The pen is getting full, and we need to take care of our little captives. Bait is chopped down into small pieces and brought along by the tagging boat so that we can feed the sharks. There is a little bit of technique involved. We throw the bait at the surface of the water with some force and it makes a splash. This alerts the sharks to the bait and after a couple days of training, they come running at the sound of the first piece of bait hitting the water. It can be amazing to watch 150+ little sharks roll and climb over each other to get the bait. This duty is the realm of the tagging boat, and the members of the tagging crew get to feed and observe this spectacle to begin their night. It passes some time before the sun sets and everyone enjoys the show. However, even this seemingly innocuous event can be dangerous. Returning volunteer Diego Cardenosa
shares a story about feeding the sharks from the tagging boat.
Diego feeds the sharks
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Another fishing night in Sharkland starts. After a good nap, the away team is ready to go and catch more baby sharks. The plan was to set the nets at 18:30, so we left the Lab at 17:30 to be there on time. After all the nets were set and the first check was done, the tagging boat started to feed the sharks with nice bite size pieces of barracuda and some pilchards. We began to throw the bait in the pen and the sharks started to be excited with the smell and the food. Matt our professional photographer wanted some pictures of the sharks "fighting" for the food and he wanted them to be in a mini feeding frenzy, so I took an entire barracuda to handfeed them. They started to bite it really hard, and one of the big sharks came and took the cuda right out of my hands and swam away with the whole thing in its mouth. So I grabbed another and another to continue feeding the little beasts. When the bait was almost gone, I tried to feed one of the big sharks and unconsciously I put my finger in the cuda´s mouth, to get a better grip. The shark was thrashing and took the rest of the fish, but then I realized that my thumb was bleeding. First I thought it might be the shark, but then I saw where my finger was...in the cuda´s mouth. So basically, I was attacked by a dead barracuda. To date, no one has gotten bit by any sharks though I have been the victim of a lot of crabs and a dead barracuda.
Lemons cruise in the pen
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Just before dinner we got our firsts sharks from Net 1 and Net 3. After dinner the tagging boat changed its captain and several of the crew were switched around from boat to boat. Joey came from Net 3 to replace Kristine Stump, who needed to be awake the next day to work with Bryan on going over some field techniques she would need for her research project. The total score for the night was 9 sharks, including 5 neonates and 4 recaptures. This leaves us with a total of 161 sharks for the Sharkland nursery area. Tomorrow we will go out to catch the rest of the sharks in Sharkland.
I am very proud to be part of this amazing crew of PIT 2009!!!
June 19, 2009
Sharkland Fishing - Night 6
Riding out one last time...
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So tonight is it. The last night of fishing for both the Sharkland area of the lagoon and this year's PIT census project. Spirits are high as the team knows the end of the long journey is in sight. The skiffs speed across the flats to their positions and the word to set the nets rings over the radios. The nets hit the water and the countdown begins. Tonight should be a relatively slow night, with few sharks theoretically left in the lagoon to capture. Everyone is fully prepared for more hours of mostly empty gillnets.
As the sun sets on the lagoon, the team settles in to the usual routine. The tides have been getting progressively larger, and the team will have to deal with deep sections at high tide, strong currents as tides change, and very shallow water at low tide.
Matt deals with a fiesty lemon
Photo by K. Gledhill
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The water hit its highest point shortly after sunset. The timing of the tides would result in another early food run tonight. The teams grinded out check after check in the deep waters, sometimes pulling the nets up to make sure there weren't any sharks near the bottom where it was difficult to see. Other than the high water, it was a pretty nice night. The winds were not too strong, and while there were some storms on the horizon, none decided to detour our way. The relative calm left the door open for some bugs to come out though, and while not terrible, there definitely was an intermittent buzzing in our ears. Before long the bright light from the food boat's Q-beam could be seen in the main channel. All the boats timed their checks so that they could all congregate at the tagging boat for dinner. While getting a nice hot meal is always one of the highlights of the night, this one was a little bittersweet, as it will be the last food run of PIT. Dinner was also special tonight - Hollie's Hot Dog Hot Pot. The pasta and hot dog dish was an old recipe borrowed from Hollie's mother that eloquently spoke to everyone's affinity for comfort food. All too soon, watch alarms went off and the net boats were called back to their posts. The skiffs scattered from the main pen, each boat's passengers with full bellies and slightly heavy hearts.
Joris expertly pilots a skiff
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The night continues its slow pace but still holds a surprise or two. We aim to fish until all the juveniles are caught, but inevitably a few lemons usually find some way to avoid our nets. In theory, we should catch zero sharks on the last night, but it never quite works out that way. Tonight is no exception, as Net 1 calls in the capture of a straggler. This is good news for the tagging boat, whose crew is happy to jump up and have a workup to complete. Net 2 and Net 3 don't want to be left out of the party and each pick up a shark of their own. In all, the total for the final night is 3 sharks. Having every net contribute on this last night is a very fitting end indeed. These last 3 bring the grand total for Sharkland to 164 sharks. Combined with the 91 shark captured in the North Sound, we have managed to catch and record data on 255 juvenile lemon sharks in the Bimini Lagoon. The attention to detail and rigorous dedication to our time-proven methodologies helped us extend our streak of low sampling mortality (5% or less) for another year. Finally the call to haul the nets rings out and the last couple feet of net are removed from the water. The fishing is over, and PIT 2009 is officially in the books. The entire team heads home with the warm glow of satisfaction that only a job well done can bring. The team will rest up, gear will be cleaned, repaired, and stowed away, and the big release of the sharks from the pen will all commence in the next two days.
June 20, 2009
Sharkland Fishing - The Aftermath
Sean - elbow deep in repairs
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The new day dawns, and the team faces the large task of trying to bring some organization back to the Lab. For the last three weeks, the hurricane that is the PIT project has wreaked havoc on the Lab. Equipment and personal gear have been used and reused, lost and found, and maybe even lost again. All the equipment and personal gear can now be piled up and sorted. Everything is thoroughly cleaned and faulty or damaged gear put aside to be repaired. Slowly the chaos transforms into neat piles which then disappear as all the equipment is returned to its proper place in cabinets, closets, or sheds.
This year has gone pretty smoothly, with no major mechanical problems. The new Sundance Skiffs performed admirably in their first
PIT tour of duty. The Sharklab Suburban and trailer were able to shuttle all our team members and equipment without a hiccup. In past years we have had to deal with boats, trucks, and pump failures. Everything around the Lab gets a lot of use, and the environment can be particularly hard on vehicles and equipment. Sean has done an amazing job of keeping things running, and his regimen of maintenance pays dividends.
The smooth running of the truck and boats afforded Sean some time this morning to give the golf cart a good once-over. The first step was inspection and cleaning of everything on the cart, including the battery compartment and connections. Parts were disassembled, lubricated, and rebuilt. Sean even replaced a deteriorating brake line. Preventing a problem before it happens is always the best policy - especially when it comes to brake failure...
A stomach eversion procedure
Photo by K. Gledhill
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A small team headed up to the main pen in Sharkland to complete some stomach eversions on two juvenile lemon sharks.
Some species of sharks have the ability to spit their stomachs out of their mouths. The best analogy we have for this is pulling a gym sock inside out. This behavior allows the sharks to get rid of shells and bones that may take a long time to digest. We use this behavior to our advantage as a way to study the diet of sharks without having to kill them. In most traditional dietary studies, a number of specimens are collected, killed, and their stomachs cut out and opened. The contents are then analyzed. Since lemon sharks can naturally spit their stomach out, we have the advantage of being able to sample what they eat without having to sacrifice them. We anaesthetize the shark using a small amount of a compound called MS-222. Once the shark is asleep we hold it upside down and slide a long pair of forceps up their gullet. The back of the stomach is gently pinched, and the stomach is carefully teased out of the shark. Anything that was in the stomach falls out into a tray below the shark. The stomach contents are then bottled and labeled for later analysis.
Everting a small shark
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Once the stomach contents are secured, the stomach is returned to its normal position. The final step is to revive the shark, usually accomplished with a combination of blowing water over its gills with a small bilge pump and walking the shark around. The entire eversion procedure takes no more than 5 minutes, but we usually try to keep the procedure down to 3 minutes. The less time a shark spends anesthetized makes a big difference in how quickly and strongly it revives. Today we had two small sharks with very full bellies. Shark number one surprised us with identifiable tentacles in its stomach. This shark had caught either a reef squid or small octopus - a really interesting find! The second shark had what was easy observable as a decent sized fish in its stomach - most likely a yellowfin mojarra, one of their preferred prey items. We are collaborating with an old Sharklab alumnus, Dr. Demian Chapman,
to scientifically test a long held truth. Predators like sharks are expected to prey on the weak and sick members of a prey population, thus increasing the fitness of the population by eliminating those genes from the pool. Demian wants to test this theory using the mojarra, specifically by testing the genes associated with the immune system. We need to collect mojarra samples from shark stomachs and compare them to samples from the natural mojarra population at large. The percentages of certain genes or lack of certain genes will be compared between the general mojarra population and the victims of the sharks to see if there are any significant differences. A big difference would show that sharks do indeed pick off the "less fit" individuals, while little to no difference would refute the commonly accepted theory. Just another piece to add to the puzzle in our understanding of the lemon shark.
We head back to the Lab, hoping that the fish in the stomach contents will turn out to be a mojarra and serve as a datapoint for Demian's study. Tomorrow we will gather the whole team together for the culmination of PIT - the release of the sharks from the Sharkland main pen.
June 21, 2009
Sharkland - The Release
text by Marissa Wiganowkse, Volunteer
The team snorkels in the Sharkland main pen
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Just when you begin to think that PIT is over, everyone is up for just a little bit more! Like they say, every beginning comes from some other beginning's end. So it’s the end of gill netting and time to release the 150+ Juvenile Lemon Sharks from the main pen in Sharkland. Everyone involved in this years PIT has given his or her all, and the result is an incredible outcome. With the same passion and goals in mind, everyone went up to Sharkland for the release of the sharks and the break down of the main pen. Putting the last few weeks of hard work behind us, it felt good to be completing the last task together with the entire crew present. After arriving at the main pen with numerous skiffs and the Pro Line, almost everyone snorkeled around with the sharks one last time. It was such a magnificent sight to see them all together up close and to think about them dispersing across the lagoon to resume their lives.
A final lap before being released
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All the while, Matt took photos, and Jim and Sean took video. When it came time to release the sharks and the pen door was opened, the sharks just did not seem to want to leave. The first few sharks out the pen door pulled a sharp "U" turn and swam right back in to continue schooling with the others. It provided us all with some amusement for awhile, until the sharks really just would not leave the pen. Several of the crew had to get in and herd the sharks out while we took down the mesh on an entire side of the pen. With time and a bit of help they eventually swam out. Reluctantly but steadily, the sharks slipped away one by one back to the lagoon. Then the deconstruction of the pen really began. It went quite quickly with cinderblocks in one boat, pen mesh in another, and rebar in others. All the pen materials and team members piled into the boats, leaving little trace of our invasion into the lagoon in the preceding weeks. Full boats made for a slow ride back to the Yacht Club, but we were kindly greeted there by swarms of sand flies. All the materials were loaded on the truck, and the boats were brought around the South island and back to the lab. As a final reward, the boats were treated to a brilliant sunset cruise as they sped along the length of Shell Beach on their way home.
Observing the lemons before their release
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With PIT completed, one last deep vertical line seemed like a must, and who wouldn’t be stoked to do one! While one crew set the deep line others continued to fixed gill nets - guess we just can’t get away from them. After the deep line was set for a few hours, everyone rode on the Twin Vee, Pro Line, and with Katie and Grant on their Twin Vee. With lots of anticipation and high hopes for a big Tiger Shark or something new to us all, everyone was on edge. Agonizingly slow the line was brought up and empty hook after empty hook came onto the boat. Finally, we were rewarded by gangion 11. We all got what we were looking for, a 3+ meter (12 ft) male tiger shark. The current was ripping, not making for ideal work up conditions for you could see how difficult it was for Emily to keep up while filming. All went smoothly and the shark was on its way after taking measurements, DNA, and tagging it. It was a thrill to see one last big shark with the entire team assembled. On the way back in, those of us who were on the Pro Line and with Katie and Grant all jumped in for a swim, a nice touch at the end of an extraordinary three weeks of PIT 2009.
The fishing is over and the PIT 2009 Juvenile Lemon Shark Census is complete.
To see some of the data collected this year and get a review of the project please see The Rundown
