It’s already been a week since I arrived in South Africa to study the endangered Knysna seahorse with Dr. Louw Claassens from the Knysna Basin Project. Together we are testing if environmental DNA (eDNA) can be used to find rare seahorses and pipefishes.

eDNA filtering in progress

To do this, we have been travelling along the southern coast of South Africa, taking water samples along the way in estuaries where our focal species lives, where it used to live, or where it might live. Yesterday we left Knysna to sample water in Klein Brak and Groot Brak. We are especially interested in the Klein Brak estuary, since there are multiple anecdotes that the Knysna seahorse (Hippocampus capensis) used to live here. Nobody has checked recently if it really was the Knysna seahorses and it seems that the most recent sighting has been many years ago. Because of this, it is usually assumed that there are no more Knysna seahorses in Klein Brak.

This brings me to a very important (maybe the most important?) question about this whole endeavour: WHY are we actually doing this? It’s all good an well to say that we want to help these endangered animals, but what exactly are we hoping to achieve? What will our results mean for managing the endangered Knysna seahorse, the critically endangered Estuarine pipefish, or any other endangered small fish for that matter?

Knysna estuary, just imagine all the seahorses down there!

What we are hoping to achieve can be summarised in three main points.

1. We want to test if the eDNA method can really be used to find small, endangered fishes (particularly seahorses and their relatives). So far, previous research has shown that eDNA work on large fishes such as sawfish, but it is not sure yet if this will work for seahorses, which are obviously much smaller.
2. The best case scenario would be that we could also find seahorses in estuaries where it was thought to have disappeared. This would be great news for the conservation status for the species, as it would mean that it occurs in a wider area than we thought, which would mean that it is less likely to go extinct.
3. If this would happen, it would mean two things. First of all, the new locations would have to be studied, so we can find out how many live in these estuaries. It would also mean that those new places need extra protection and monitoring to ensure the species do not disappear from their newly discovered homes.

Ultimately, if the eDNA method works for small, endangered seahorses (or their relatives), it could be used to monitor small fishes worldwide. This would help solving one of the biggest problems with studying small species, especially those that are rare or hard to find.

Louw looking for Knysna seahorses in the Thesen Island Marina (she found 3!)