When Louw Claassens talks about Knysna seahorses, there is a fire in her eyes. Her love affair with this iconic estuarine species (Hippocampus capensis) began after a chance meeting during a field trip with well known local Professor Brian Allanson from the Knysna Basin Project. At the time, she was studying for a Masters degree in Aquatic Health at the University of Johannesburg. The experience so inspired her that after graduating, she moved to Knysna, joined the Knysna Basin Project, shifted her field of study and made researching the status and distribution of the Knysna Estuary's most celebrated aquatic resident her primary mission.
Knysna seahorses are incredibly rare. They have the smallest geographical range of any seahorse and can be found in only three estuaries: Knysna, Swartvlei and Keurbooms. They are unique in that they are the only known true estuarine seahorse species in the world. They are classified by the International Union for the Conservation of Nature (IUCN) as endangered which makes the study and protection of the species critical. The study of seahorses is also extremely valuable because they serve as an indicator species, due to the fact that they are extremely sensitive to the adverse changes in the natural environment. A flourishing Knysna seahorse population could therefore, be indicative of a healthy estuarine system, or vice versa.
Collecting the data is essential. Few people are aware of the importance of the health of the Knysna Estuary. It is the most significant in South Africa in terms of species biodiversity and the protection of fauna and flora in the Knysna Estuary alone would ensure that 42% of South Africa’s estuarine biodiversity is conserved.
Under the banner of the Knysna Basin Project, a non-profit organisation that for nearly twenty years has been involved in monitoring the health of the Knysna Estuary and the impact of human development on this estuarine system, the Knysna Seahorse Status (KySS) project was launched in 2014 and forms part of Claassens PhD study through Rhodes University.
In order to establish the distribution and abundance of the species, researchers need to survey the populations across various habitats and see what, if any, patterns emerge. “Very quickly we found a consistent pattern of considerably higher population densities of the Knysna seahorse within the artificial (gabion) structures of the Thesen Island Marina, as a opposed to their natural habitat, such as eel grass beds” says Claassens.
The project researchers then went on to do 'habitat choice' experiments, where they placed two cages in the marina, one containing the artificial habitat and one containing the natural vegetation. What they found, was that the seahorses almost always preferred the artificial structures when given a choice. There are several theories as to why the Knysna seahorse seeks refuge in the canals of Thesen Island and this all forms part of the study. Much remains unknown.
“The question we have to ask now is “are they thriving here, or are they merely surviving?” Claassens aims to continue her quest once she has completed her PhD this year and if she receives adequate funding she will go on to do her Post Doctorate in order to further study this remarkable species. She hopes that her research can one day also be used for the international conservation of seahorses. Sadly, seahorse populations are threatened in many parts of the world. This is due to habitat destruction, bad fishing practises, and the exploitation for use in traditional medicines.
Claassens believes a lot more needs to be done to manage the species and the estuary as a whole and in order for research and conservation efforts to be successful, public awareness is key and Claassens is passionate about educating the public. The Knysna Estuary needs inspired custodians.
One thing is for certain - Knysna gained a genuine asset the day Louw Claassens decided to make the study of the Knysna seahorse and the estuarine system within which it finds sanctuary, her life's mission!