It’s common knowledge that the removal of apex predators from the food chain spells disaster for the ecosystems concerned. However, if you don’t know what numbers you’re dealing with, how the heck are you supposed to manage the situation? This is exactly the dilemma Dyer Island Conservation Trust (DICT) marine scientists, specialising in Great White shark research find themselves in. Their answer? Find someone willing to help develop more high-tech, affordable tracking tags so they can conduct their research in a more meaningful, comprehensive manner.
This startling fact was brought to our attention by predator researcher Michelle Wcisel during a recent PM reader’s event held at DICT’s Gansbaai facility. According to her, it’s frightening how little they understand about the Great White’s habits and movements. “In South Africa, the current total population estimate is a total thumb suck of about 2 000 animals, but our research indicates that this may well be an over-exaggeration. We also have no idea what their migratory ranges are, or for that matter, where they breed. Basically, every time we tag an animal the book gets rewritten.”
The only way to know for sure what’s really going down is to track as many animals as possible, but here’s the rub – all three tag types used to monitor Great Whites are not only prohibitively expensive (effectively putting the volumes required out of reach of DICT researchers), but also underwhelmingly low-tech devices with minimal functionality. Says Wcisel: “When you consider the amount of cheap technology packed inside your average cellphone, it’s shocking to think how basic the current tag designs are.”
Limitations of current tag design
Currently, three tag types are used to track Great Whites: Acoustic, PAT and SPOT.
Acoustic tags are attached via a barbed end that’s jabbed under the shark’s skin. All they do is release a continual acoustic ping, so something must be in the water to hear it – whether that’s a research vessel or a bottom-mounted listening station. Basically, they just tell you the presence/absence of a shark as long as something is “listening”. The tags fall away within a year or two and leave no damage to the shark.
These tags cost around R1 400 each and bottom receivers go for over R45 000. Manual tracking requires a hydrophone system priced at around R10 000 a pop, then there’s the costs of running the boat and paying the skipper. Says Wcisel: “We are currently trying to secure funding for 10 bottom mounted receivers for our bay. However, this option isn’t feasible for monitoring long-distance movement, something that’s critical if we want to understand and conserve this species.”
PAT tags are attached in the same way as Acoustics. They archive data, including a location based on the level of the sunlight the tag detects (opening them up to huge error margins), the depth the animal is swimming, and sometimes temperature. These tags are limited to 3-6 month deployments and then “pop-off”. Its then up to luck whether the researchers retrieve the tag and get to download the data. These go for around R37 000 each and require between R3 000 and R5 000 worth of satellite time per month.
SPOT tags get attached by bolts or strong barbs to a dorsal fin. Says Wcisel: “For sharks, this means catching and releasing the animals, which none of us like to do! It’s risky to sharks and the media attention these campaigns garner is very negative.” Once attached, SPOTs transmit every time they sense they’re outside of the water (by a break in the connectivity) and the data transmitted is in real time. However, they only transmit the tag’s position, no depth or temperature data is included. They do detach over time, but have one serious down side – they can leave the shark with a permanently damaged dorsal fin.
These cost about R18 000 apiece and then the same amount of satellite time as the PAT tag option. Wcisel elaborates: “Currently we have 34 Great Whites fitted with SPOTs and, considering each one is expected to last about five years, that means an outlay of about R355 000 for satellite time alone!”
The ideal tag
The way Wcisel sees it, the ideal tag would be a small unit that one could easily deploy on a free-swimming animal, that can transmit real-time data, and that can record accurate position, depth and temperature. Other considerations such as a proper anti-foulant to keep algal growth off, as well as clean tag detachment must also be considered. Wcisel points out: “The frustrating thing is that all the technology required to make this happen already exists, it’s just that no one has thought to put it all together yet!
Says Wcisel: “Considering the availability and the incredible advancements in current technology, there is no excuse that animal telemetry is not an easy to conduct, open access endeavour. Imagine if you could log onto Google Maps and see where Bessie the white shark is swimming or where Tommy the green sea turtle goes? Can you imagine the impact on education and conservation work if tagged animals were now teaching us the inner workings of the ocean, highlighting the most crucial areas, not us just guessing?”
Call to arms
So, if you’re a Masters student looking for a worthy project with global ramifications, or are an electronic geek with some extra time on your hands, contact DICT – these guys could really do with your help. For those considering DICT’s call to arms, Wcisel has this to say: “If you do have a more effective and affordable tag design, please contact us or, even better, give us a visit – we can be your laboratory. After all, we have the resources available to test your designs; we just need the new technology!”
The DICT outing, arranged in collaboration with VW South Africa, focused attention on its three-pronged “Think Blue” initiative. Sixteen lucky PM readers drove a selection of Volkswagen cars, including the Touareg, cc and Golf, giving them a chance to experience the brand’s Blue Motion technologies . Once there, they learned about shark behaviour, the science of shark tagging and the ongoing effort to protect these critically endangered animals from the depredations of humans. They also experienced a memorable cage dive, getting up close and personal with Great Whites.