Catshark Tagging in De Kelders

When I applied to the Marine Dynamics Academy Scientific Internship programme I was aware of the conservation objective which was the tagging of small sharks in the local marine ecosystem. Of the many species of sharks in South African waters, the small sharks are sometimes overlooked largely due to the presence of larger shark species such as the bronze whaler shark and the most famous shark species in the world, the great white shark.
In my short time in this wonderful place, I have gained a greater appreciation for the value these small sharks bring to the benthic community.

The most common species of catsharks in the Western Cape are the pyjama catshark (Poroderma africanum), the leopard catshark (Poroderma pantherinum), the puffadder shyshark (Haploblepharus edwardsii) and the dark shyshark (Haploblepharus pictus). They are benthic sharks which means they primarily feed on the seafloor. Their teeth are small and have the consistency of coarse sandpaper. Catsharks usually feed on crustaceans, small fish and cephalopods. The size of the sharks depends on the species but they usually do not exceed 110 cm, with the pyjama catshark being the largest of the South African inhabitants.

My first experience with the catsharks, besides the interesting lectures on attracting them using bait and their behavioural habits, was going snorkelling in a neighbourhood to the north of Gansbaai, named De Kelders. The briefing beforehand involved detailed instructions on how to catch catsharks. We were told that they have a habit of curling up into balls for defence when they are handled and that when this happens, not force the animal open as they have skeletons made of cartilage and too much pressure could potentially damage the musculoskeletal system of the shark. The best way to handle the sharks is to gently grab them on the ventral side of the shark behind the gills and pectoral fins so as to not damage the gill structure. It is also best to grab them firmly but not to squeeze. The tagging we used was ORI tagging which consisted of two different tags. The A-tag is used for animals between 30 and 60cm and the D-tag is used for animals over 60cm in total length. This tagging is used to track the distribution of these sharks.

The process of catching them involved snorkelling, which was a very exciting venture for me as I had never been snorkelling before. The area we snorkelled in was a small inlet in the shoreline 3 meters to 6 meters deep. The area was a growing kelp (Ecklonia maxima) grove which was perfect conditions for catsharks. There was a bait canister that we put in the water prior to any proper snorkelling. The bait consisted of sardines which are very oily so they put out a decent scent trail. Snorkelling was an enjoyable experience and we caught two dark shy sharks on the first dive. There was a nearby rock pool which acted as storage for one shark while we looked at the other. The total length was taken as well as the inter-dorsal length. The first shyshark was too small to tag but the second one was over 40cm in length, so he was tagged with a D-tag. The release of sharks consisted of holding the tail and the underside of the shark holding it in the swell of the incoming tide and releasing it when the water is taken back out to sea. The third and last shark caught was a leopard catshark, a female measuring over 60 cm in length. This warranted an A-tag which I had the honour of doing. The tags have a small plastic barb on the end which is inserted using a metal rod. The tag was inserted parallel to the vertebrae so the plastic barb was below the epidermal layer securing the tag. The shark was then held in the incoming waves until she swam back into the depths.

The experience of snorkelling has increased skills that I will no doubt need to further my future career in marine biology and help in my understanding and appreciation for the magical and awe-inspiring world hiding under the water’s glassy surface.