Shark Tagging Expedition
Our interns provide the lowdown as to what they captured and the importance of what they're doing
Written by Caitlin Brader, Camille Ollier, Marena Long, Jan 23 2019
Why tagging small sharks?
Small sharks are little known. As well saying “small” sharks, they are mostly forgotten in the marine ecosystem, but they are as much as important as the other species. Tagging of small sharks includes the Dark shyshark (Haploblepharus pictus), the Puffadder shyshark (Haploblepharus edwardsii) the Leopard catshark (Poroderma pantherinum) and the Pyjama shark (Poroderma africanum), which will enable us to collect data in order to better inform management and conservation strategies.
The catch, tag and release process is an important component of the internship. The data will provide us information on the distribution and numbers of these small shark populations. We catch, tag and release as part of ORI’s (Oceanographic Research Institute) Cooperative Fish Tagging Project (ORI-CFTP). This program involves the voluntary cooperation of conservative anglers (by tagging and releasing the fish they catch) with the intention to monitor and conserve South Africa’s marine life in a sustainable manner.
Are they threatened?
Some of them are on IUCN red List, the Leopard catshark as data deficient and the Pyjama shark as near threatened. We only tag these sharks as priority species. The dark shyshark and the puffadder shyshark are not tagged as they are abundant but could be threatened in the future.
They are not really threatened by fishing because they are not target species, but some anglers do consider them as a bit of a pest and are not always treated in the most humane manner.
We went out fishing with Ettiene. Prior to this fishing trip, Ettiene had showed us the ropes (or fishing lines, in this case) on the basics of fishing. We learned how to tie a few knots, prepare the bait and cast the line. We did attempt to fish last week after this practical lesson, however it proved unsuccessful as it was a no sea day and the ocean was subsequently a tad rough…
Luckily, this week’s trip took a turn of events! We went out to Stanford’s Cove and it was a lovely day. It started off fairly quiet, we casted a few lines and waited for a bite, as you do. But then, as unexpectedly as ever… Caitlin caught a shark!
Once we caught the shark there was a few things we needed to do pretty quickly so we didn’t cause stress to the animal. Firstly we had to identify which species it was. This was a little difficult because the puffadder shyshark and dark shyshark sometimes crossbreed resulting in hybrids. So, genetics would be a plus in studying the shark populations.
This particular shark looked a lot like a puffadder shyshark as he had some slight orangey tinges in the photos but more like a dark shyshark due to his darker coloration when we were identifying it. In the end, we agreed to call it a puffadder with possible cross with a dark shyshark.
Next, we had to get a measurement of the shark. The curious fact about these sharks, in case of capture, they could be agitated and they curl themselves up for defense (and that’s why we call them shyshark because they look shy when they behave in that way). We just have to cover their eyes with our hands and we could also massage their nose to calm them down. With gloves on, Ettiene and Marena held the shark as straight as possible to get a measurement.
When measuring these small sharks we use total length. This is the length from the shark’s nose to the tip of its tail. We laid the tape measure underneath the shark and read how many centimeters from a perpendicular angle. This shark was pretty big, coming in at 53cm. Next Ettiene checked the sex of the shark by looking at the pelvic fins and as this shark had claspers, it was a male. Based on the size, you can also infer how mature the shark is, but just like humans size can not always definitively predict maturity. The shark Caitlin caught was a sexually mature male with one deformed clasper (we could tell of this due to the claspers underneath of the shark). We took a few photos of the shark, both with and without the measuring tape underneath to show its size. Finally, it was time to gently release the shark back into the ocean.
So, what do we do with all this data? All the information we recorded: species, size, sex, maturity, and any notes, goes into an excel spreadsheet. This way all the information is stored in one place and can be easily accessed later on. This can be especially important if a tagged shark is recaptured. It also allows us to easily share information with ORI.