Yesterday we watched the antics of a film crew in Bimini harbor swimming around at a boat dock across from us with baited Bull Sharks in an attempt to place a “fin cam” on the back of an animal. Sadly, as they discovered, the shark site they chose …
Da Shark has discovered a new shark blog and after just two posts we have become fans.Of course that’s also after a few Kalik Beers at one of our favorite Out Island Bahamas watering holes that happens to have crackin’ Internet.And why, you might well …
There’s a new paper from Guy Harvey’s team about Cayman Island’s hugely successful wild animals encounter, “Stingray City” and what rampant and uncontrolled commercialism of species does to feeding and movement patterns.Oh and it’s not good, in fact it…
We just found this website and we have to say it’s a great idea and perhaps an actual solution or stop gap measure to the question of shark sanctuaries and enforcement. Welcome to the fine folks from HEPCA who have had enough of sharks being taken from…
Has it been a decade over there in Fiji?
Looks like it and now we have research driven data as well.
The kind of data that helps an entire industry grow, the kind of data that Fiji and the Team at BAD are so good at initializing and producing – quality work.
If you thought today’s blog post from Fiji and Da Shark was celebratory, you were correct, and congratulations are in order as well for the entire Fiji team who have fearlessly, “done their own thing,” and in doing so laid out a template for sustainable shark diving the world over.
We have long been fans of BAD and Da Shark, and no we’re really not secret investors, we just have an eye out for excellence in the shark diving community and Fiji consistently fires on all cylinders when it comes to commercial shark diving, conservation, and research.
So Kudos to all for this latest paper and another continued decade of adventures to all:
Opportunistic Visitors: Long-Term Behavioural Response of Bull Sharks to Food Provisioning in Fiji
Juerg M. Brunnschweiler, Adam BarnettAbstract
Shark-based tourism that uses bait to reliably attract certain species to specific sites so that divers can view them is a growing industry globally, but remains a controversial issue.
We evaluate multi-year (2004–2011) underwater visual (n = 48 individuals) and acoustic tracking data (n = 82 transmitters; array of up to 16 receivers) of bull sharks Carcharhinus leucas from a long-term shark feeding site at the Shark Reef Marine Reserve and reefs along the Beqa Channel on the southern coast of Viti Levu, Fiji.
Individual C. leucas showed varying degrees of site fidelity.
Determined from acoustic tagging, the majority of C. leucas had site fidelity indexes greater than 0.5 for the marine reserve (including the feeding site) and neighbouring reefs. However, during the time of the day (09:00–12:00) when feeding takes place, sharks mainly had site fidelity indexes smaller than 0.5 for the feeding site, regardless of feeding or non-feeding days.
Site fidelity indexes determined by direct diver observation of sharks at the feeding site were lower compared to such values determined by acoustic tagging.
The overall pattern for C. leucas is that, if present in the area, they are attracted to the feeding site regardless of whether feeding or non-feeding days, but they remain for longer periods of time (consecutive hours) on feeding days. The overall diel patterns in movement are for C. leucas to use the area around the feeding site in the morning before spreading out over Shark Reef throughout the day and dispersing over the entire array at night. Both focal observation and acoustic monitoring show that C. leucas intermittently leave the area for a few consecutive days throughout the year, and for longer time periods (weeks to months) at the end of the calendar year before returning to the feeding site.
About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at sharkcrew@gmail.com.
We have over 370 individual Great White Shark identified at Guadalupe Island. The Marine Conservation Science Institute has been keeping track of these awesome animals since 2001.
Lets look at what makes these unique and the methods we use to identify them. The first thing we determine is the sex of the sharks. Male sharks have claspers and Females don’t.
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| Female Shark, no claspers |
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| Male shark, claspers |
Once we know the sex of the shark, we look at the pattern of the transition from the white belly to the grey top. This transition is like a fingerprint. We primarily look at 3 different areas of the Shark. The gills, pelvic area, and the tail.
Lets look at this picture of a Great White Shark and identify it.
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First we need to determine the sex of the shark. So lets take a closer look at the pelvic area. We can see that there are no claspers, so it is a female.
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| No claspers, = female shark. |
Now that we know that is a female, we look through our database and try to match up the color pattern to the females we have in our database.
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| #262, Deb |
I think we found a match #262, Deb, looks like a perfect match. What if we are not convinced? In that case we look at another area. How about the gills?
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| Left is our photo, right is our databese |
As you can see, the color pattern on the gills matches as well, so we have a confirmed match. The shark in our picture is #262 “Deb”
Aside from the color pattern, we also look for mutilations. We have previously talked about the amazing healing ability of our sharks here, so we have to be careful to not use regular injuries as a sole means of identification. Here is a picture of”Bruce” with a big bite from another shark.
Just a year later, he barely showed any sign of that injury.
Unlike flesh-wounds, mutilations are permanent. We have many sharks that have some unique mutilations, like the famous “Lucy” with her mangled tail.
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| Lucy |
However, even with mutilations we have to be careful. There are multiple sharks who may have similar mutilations, so we still have to make sure that we positively identify those sharks. At Guadalupe, “Andy”, “Chugey”, “Tzitzimitl”, and “Cori B” all have the top of their tail missing
There are other mutilations, like missing pieces of a pectoral, pelvic, or dorsal fin that can all be used as a preliminary identification, but like mentioned above, it’s never a sole means and always has to be confirmed by looking at the color pattern.
Many people, especially on social media are using “birth marks”, black spots on typically the white belly of the shark, to identify the sharks. Those are actually not birth marks at all, but rather copepods, a parasite that can move around and may disappear from a shark, so they are not a good way to identify our sharks.
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| “Tzitzimitl” with copepods. |
All of our divers receive a copy of the entire Photo ID Database witch contains every shark we have identified at Guadalupe Island.
Now that you know how to identify the sharks, you are ready to come shark diving with us. How great will it be when you watch “Shark Week” the next time and you’re able to say “this is the shark that swam right by me”. Our goal is not to simply get you face to face with Great White Sharks, but to also share everything we know about all the individual sharks we encounter. Some individuals we have known for 21 years and watched the grow from “little” 12 footers to well over 16 feet.
Some of our trips are hosted by Nicole Nasby-Lucaas, the scientist who keeps the database, where she shares her vast knowledge from years of researching Guadalupe’s Great White Sharks with our divers.
Call us at 619.887.4275 or email crew@sharkdiver.com for more information on our expeditions.
Let’s go shark diving!
Cheers,
Martin Graf
CEO Shark Diver
About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.
