SANParks has successfully restocked a special display tank housing a near-mythical creature that lives exclusively in three estuaries on the Garden Route.
The display tank in SANParks’ Garden Route headquarters on Thesen Island in Knysna is one of the few places in SA permitted to house and display captive Knysna seahorses for educational purposes.
Up to 50 pairs of Knysna seahorses used to be on show but by 2024 the number had dropped to just three pairs.
The decline was primarily due to natural ageing, as most of the seahorses had exceeded their typical lifespan of five years.
SANParks spokesperson JP Louw said on Tuesday researchers had recently looked to address this situation, in line with SANParks’ Threatened or Protected Species permit from the department of forestry, fisheries and the environment.
This was read in conjunction with the exemption issued under the Marine Living Resources Act, which stipulated the maximum numbers for the tank and the required conditions.
“In a one-off restocking exercise, the SANParks researchers captured six young adult seahorses in the Knysna Estuary and introduced them into the tank to boost the breeding population and enhance genetic diversity.
“These new additions are already contributing to improved breeding success, with recent signs of spawning offering hope for a self-sustaining population in the display tank.”
Louw said the restocking initiative formed part of SANParks’ ongoing efforts to raise awareness about the endangered species and strengthen conservation education in the Garden Route National Park.
“The Knysna seahorse is found in only three estuaries in the world — Swartvlei, Knysna and Keurbooms — and all are located on the Garden Route.
“Our special display tank offers visitors a unique opportunity to view one of South Africa’s most iconic marine creatures up close while learning about the threats they face in the wild.
“These include habitat degradation, pollution and capture for trade in the aquarium and traditional Chinese medicine markets.
“Members of the public are encouraged to visit the SANParks Thesen Island office to view these fascinating creatures and learn more about the vital conservation work being undertaken to protect SA’s only endemic seahorse species.”
SANParks’ seahorse project lead researcher Clement Arendse said the seahorses introduced to the tank were collected during a snorkelling exercise.
“Individuals were captured by hand by an experienced scientist and placed into a holding bucket with oxygen supply.
“The young adults that we wanted were recognised by their size, roughly 4-6 cm.
“Sexes for seahorses are easily recognised in adults — males have a brood pouch on the tail.”
He said the last population assessment was done in 2003 and SANParks was now reassessing the population.
“We should have an estimate of population size once the study has been completed and the data has been analysed.”
He said besides assessing numbers, he and his team were also mapping other factors to better understand the species.
These included where the different populations now occurred, the distribution of their favoured seagrass habitat, availability of food and proximity of human structures and activity.
Knysna seahorses are uniquely monogamous and the only animal species in which the male bears the unborn young.
The female deposits her eggs into his brood pouch and the male fertilises them internally and carries them until they are hatched and released into the water.
Arendse said the male seahorses performed a “mating dance” to allow the female to deposit her eggs in his brood pouch.
“The male swims up and down in the water column in order to align their sex organs.”
The species favour eelgrass habitat, which provides cover from predators. They suction feed on plankton and tiny crustaceans in this aquatic jungle.
According to the SA National Biodiversity Institute, adults of the Knysna seahorse are up to 12cm long with the males being longer and heavier.
“Knysna seahorses move slowly and, to prevent being washed away by tidal currents, they use their prehensile tails to attach to submerged aquatic vegetation.”
The Herald
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