A curious, ancient looking creature grasps to its Codium anchor as sampling begins every month at low tide in the canals of Thesen Island Marina. This brownish-green resident is the Knysna seahorse (Hippocampus capensis), the only endangered seahorse in the world. This means as a student, and full-time ocean-lover, it is such an amazing experience to study these animals.
We set off just before low tide hits in the Knysna Basin Project boat armed with a pool scoop-net, a scale and calipers. Spending around an hour sifting through scoops of Codium tenue (the free floating green-black macroaglae all over the canals) we eventually find a couple of shy individuals. Transferring the surprised animals into a container of water is step one, next they need a quick measure of their head, trunk, tail and weight.
Figure 1: Nina looking for seahorses within a Codium tenue sample.
Seahorses rely on their tails to keep them from floating away with the current. So it’s no surprise they curl them around the first thing they can find, which just happens to be my finger as I do my measurements. Their sex is also noted, it’s easy enough to see as the males have rounder bellies than the females due to the job of looking after all the developing babies.
Figure 2: Transferring a seahorse into a container of water.
Figure 3: Measuring the head, trunk, tail and weight of a seahorse.
Seahorses aren’t the only thing we pull up in the pool net. A couple of speedy pipefish find their way into our sampling and they too are measured.
Figure 4: Measuring a pipefish from our sampling.
Once we’ve finished with our measurements the seahorses are safely returned to their patches. As they drift back down they vanish into the background of drifting seaweed. These masters of disguise blend in so well into their environment it’s no wonder people hardly believe that they have the privilege of seahorses on their doorstep.
Guest post written by Nina de Villiers, a Honours student from Rhodes University.
