The shark research team with the Hon. Larry Cartwright, Minister of Agriculture and Marine Resources.

One of the most unique and rewarding parts of running a research program at the Cape Eleuthera Institute is the role most of us play at our sister organisation, The Island School.  Twice a year, 48 high school students from all over the US and The Bahamas take part in a three month semester program and one of their keystone experiences relates to the primary research undertaken at the Cape Eleuthera Institute.  Every semester the Shark Research and Conservation Program takes 6-8 Island School students and guides them through the scientific process, from posing a question, gathering the data to answer that question, analysing the results and finally communicating their findings to collaborating scientists and Bahamian policy makers at the bi-annual Island School Research Symposium.

Last semester, as part of the SOSF funded research, the students undertook a study looking at the distribution and abundance of juvenile tiger sharks around Cape Eleuthera.  The Fall 2009 semester was especially privileged to have the Hon. Larry Cartwright, the Minister of Agriculture and Fisheries, present at the research symposium.  This allowed the Island School research team to discuss the the findings of their project, and about shark conservation as a whole with the minister directly responsible for generating marine and fisheries policy.  The poster of their results can be downloaded directly from here, and all the other Island School research programs from the last two years can be found here, kindly hosted by the Fisheries Conservation Foundation.

Island School student and B.E.S.S. scholar, Chrissy Darville discussing the results of the tiger shark project with the Hon. Larry Cartwright

Fall 2009 Island School Shark Research Symposium Booth.

A Caribbean reef shark in a mild form of tonic immobility whilst being blood sampled by the CEI shark team.

One of the biggest problems facing anyone interested in the physiology fish is how to generate a baseline level of blood chemistry.  What does the blood chemistry of a fish look like if it hasn’t been captured, handled, poked and prodded all in the name of science?  What are the normal levels of lactate, glucose, carbon dioxide etc., to which we can compare our “stressed” samples to?

For small fish this is relatively easy.  Take the recent work on bonefish by the Flats Ecology and Conservation Program here at Cape Eleuthera Institute.  Bonefish were housed in darkened holding chambers with a steady supply of fresh seawater for 36 hours upon which they were rapidly removed and blood sampled before the blood chemistry could change.  However, it is a tricky proposition to try and apply this technique to a 6ft Caribbean reef shark!

To try and generate a baseline level of blood chemistry for stress physiology work described in the previous post, the shark research team travelled from Eleuthera to Stuart Cove, a well known dive operator in Nassau.  Stuart Cove have been conducting regular shark dives for the last thirty years and the Caribbean reef sharks they deal with are very used to human presence in the water.  The more experienced handlers can gently halt the motion of the shark through the water by gently rubbing a chain mail shrouded hand on the nose of the shark where ultra sensitive electro-reception pores are situated.  This action appears to initiate a response similar to tonic immobility, a reversible coma-like stasis, which is usually triggered by inverting the shark.  The response initiated by the handlers is not as strong as true tonic immobility, but it was hoped that it was strong enough for a diver to quickly draw some blood, thus gathering a sample from a shark that had not been captured or interfered with in any way – a baseline.

For the most part it worked – taking blood in full SCUBA gear, laying on you back under the tail of a shark with your hands clad in chain mail was a tricky thing to do.  And although the sharks were in a mild form of tonic immobility they did not appreciate a clumsy human prodding them with needles, so unless the needle was put in the right place at the first try, they tended to swim off.  Two and a half days of diving provided us with numerous dulled and bent needles, frustrations and thankfully three blood samples.  The blood chemistry values derived from the three samples were vastly different to even the shortest longline hooking durations and represent the first true baseline blood samples taken from a large free swimming shark.

Special thanks must got to Stuart Cove himself whose generosity with his staff and boats were unparalleled.

A Caribbean reef shark blood sampled underwater.

Stuart Cove Shark Dive

Drawing Blood from a mature male Caribbean reef shark.

Small scale longline surveys are the predominant method for investigating shark populations, and when longlines are implemented on a much larger scale, are responsible for the widespread commercial harvest of sharks all over the world. Any capture event, including longline capture, unleashes series of physiological and physical disturbances, the issue is that very little is know about how this physiological stress impacts the behaviour of an animal post release, or if indeed the animal survives.

This year’s project took a two stage approach to begin to investigate the effects of longline capture on the Caribbean reef shark (Carcharhinus perezi).  Firstly, blood samples were taken from sharks that were captured during our longline surveys, using hook timers to accurately determine the amount of time the shark had been on the line.  Blood was taken from the shark and portable blood analysers were used to quantify various blood chemistry parameters which in turn indicate the level of physiological stress the shark was under for a given duration of hooking.  Secondly, a subset of fifteen sharks were equipped with acoustic transmitters which emit an ultrasonic series of pings every 45 seconds which can be detected by an array of underwater hydrophones.  These transmitters had a three-dimensional accelerometer incorporated into the tag which measured the activity level of the shark every 20 seconds post release, the data for which was in turn transmitted and stored on the seabed hydrophones.  The hydrophone array itself consisted of 32 receivers covering approximately 14 square kilometres of seabed in prime reef shark habitat.  The use of these transmitters allowed us to quantify the activity level, depth association and movement patterns of the Caribbean reef sharks post release and begin to understand how capture events might impact their behaviour.

The project officially drew to a close in November 2009 after taking blood from over forty Caribbean reef sharks and collecting approximately 33,500 detections  from the accelerometers attached to them.  The shark research team is currently collating the results which will be presented at the annual American Elasmobranch Society meeting in Rhode Island in July 2010.  The team will take part in a special symposium entitled The Physiological Stress Responses in Elasmobranch Fishes organised by Dr. Greg Skomal of Massachusetts Division of Marine Fisheries, and Dr. John Mandelman of the New England Aquarium.

An accelerometer attached to the dorsal fin of a Caribbean reef shark

An accelerometer equipped Caribbean reef shark just prior to release.

]]> http://www.saveourseas.com/blogs/cei-bahamas/2043/feed 0 http://www.saveourseas.com/blogs/cei-bahamas/1942 http://www.saveourseas.com/blogs/cei-bahamas/1942#comments Sat, 17 Oct 2009 13:59:04 +0000 Edd Brooks http://www.saveourseas.com/blogs/?p=1942 So its been a really really long time since I last posted – what can I say things have been busy!  There has been so much going on that keeping the blog up has fallen by the wayside a little bit.  I will endeavor to keep things a little more current and update you all on the huge backlog of happening over the last five months including our work on tonic immobility in the lemon shark, the stress of longline capture in the Caribbean reef shark and how that effects behavior and survivorship, the abundance and distribution of sub-adult tiger sharks.  There has be a lot going on!

The first update I wanted to fill you in on is the presentation of our work at the annual American Elasmobranch Society in Portland Oregon in July of this year.  The CEI Shark Research and Conservation Program produced a poster presentation on the first year of SOSF funded research based on the validation of Baited Remote Underwater Video Surveys (BRUVS) and a more conservation based alternative to more traditional longline surveys.  The poster is a preliminary analysis of the results with a full manuscript to be submitted by the end of this year.  In addition, I presented on on the seasonal abundance, demographics and habitat use of Caribbean reef sharks.   Both the poster and presentation are attached to this post so happy reading if you are interested!

The shark research team at CEI is ever growing with a total of six full time researchers and field assistants – add to that this semesters Island School group and we have a total of twelve people actively working on shark research and conservation – not bad for a program which is only just over a year old.

These twelve researchers are currently split between two major projects and as such getting everyone in one place at one time is challenge – so when it happened organically I grabbed the opportunity to get a team photo.  The program would not be where it is today if it wasn’t for the help, insight and dedication of everyone in this photo and many people who have come before them – thanks everyone!

The number of projects the program is tackling is growing, and we have big plans for the future.  The first year of research into validating baited underwater video surveys against longline surveys is nearly at an end, the results of which, along with some insights into the Caribbean reef shark populations off Cape Eleuthera will be presented at the American Elasmobranch Society meeting in Portland this July.  We are currently finishing a study into the stress physiology of juvenile lemon sharks and how well they can recover from exhaustive exercise.

Highlights for the near future include -

June 2009 – The start of a study into the effects of longline capture on the behavior and survivorship of Caribbean reef sharks.

September 2009 – A study looking at the site fidelity of juvenile tiger sharks (See pic below).

And we have all sorts of plans for 2010 so stay tuned!

Today – Tuesday the 18th May 2009, marks the official launch of an initiative that the Cape Eleuthera Institute is very proud to be a part of.  The new website for the shark free marinas initiative is now live and you can see it at www.sharkfreemarinas.com. The shark free marina initiative is a voluntary association of resorts and marinas who have taken notice of the threatened status of many species of shark, and have now banned the landing of any dead animals.

The goal of the shark free marina’s initiative is to reduce some of the 391,800 sharks caught and killed by recreational anglers in the US every year, most of which are utilized for nothing more than a set of jaws on the wall and a couple of photographs.

The initiative is not seeking to curtail the recreational fishing of sharks, but instead to work collaboratively with recreational fishermen to encourage catch and release.

Please visit www.sharkfreemarinas.com

The tag – as so many do – popped off after only a week, but in that week the shark had crossed the Exuma Sound, passed through the Exuma Islands, and was mid way across the Tongue of the Ocean when the tag popped off.  That’s a journey of 120km in only a few days.  More on what the shark got up to whilst crossing all that deep water when I have had a chance to look at the data.

I will leave you with a number of truly amazing photos courtesy of Mr. Tom Peschak – Thanks Tom!

So a little while ago the son of one of our visiting scientists was wandering the docks of the local marina and spotted a large bull shark.  Unfortunately the shark was dead, killed in the early hours of the morning by a group of guys who were having a party in which the side entertainment was killing this young female shark.

The recreational fishing of sharks represents a small but significant source of mortality,  In 1999 approximately 5.7 million sharks were landed by US recreational anglers with a large proportion of that catch released alive.  There are no figures available for The Bahamas.  Sharks are arguably the most threatened group of species in the world and the killing of this animal represents a huge waste, no part of the animal was used, the only goal was killing for the sake of killing.

Now this story has a happy ending for two reasons.

Number one, we retrieved the shark and the students from The Island School and the Spanish Wells All Age School were given an impromptu dissection and lecture on shark anatomy, conservation and biology.

Number two the General Manager of the Cape Eleuthera Marina and Yacht Club has agreed to join the Shark Free Marina Initiative.  This initiative was designed as an open source concept by Patric Douglas of sharkdivers.com and is a voluntary scheme to which any marina or yacht club can join. Cape Eleuthera Resort and Marina has now adopted this scheme and no more sharks can be landed there.  Thank you CapeE!

I also want to say welcome back to Chris Berry who is sticking around for his third season of sampling with us as well as talking on significant responsibilities at The Island School.

Thanks guys!!!

Another thanks must go to SOSF very own Tom Peschak for all us to use the image of Chris and Alana on this post.