The Distribution and Ecology of the Endangered Knysna Seahorse (Hippocampus capensis Boulenger, 1900) in the Thesen Islands Marina, South Africa

21 Sep 2015 Thesen Islands Marina, South Africa, Africa Fishes

Louw Claassens


Other projects

21 Jun 2017

Ecology of Hippocampus capensis (Pices: Syngnathidae) with Specific Focus on Site Fidelity, Home-Range Extent and Habitat Availability

A description of the natural history of the Knysna seahorse (Hippocampus capensis) within a tidal marina estate in the Knysna Estuary, South Africa.

Seahorse found within the larger Knysna Estuary within Eel grass.

Seahorse found within the larger Knysna Estuary within Eel grass.

Hippocampus capensis is listed as Endangered on the IUCN Red Data List (Hilton-Taylor 2000) due to its limited distribution range, small population size and habitat vulnerability. It only occurs in three estuaries along the southern coast of South Africa. Since the last population survey of 2001 (Lockyear et al. 2006) extensive developments have taken place within the Knysna Estuary, including the construction of the Thesen Islands Marina, a 90.6ha residential marina estate. The development added 25ha of new additional estuarine habitat to the Estuary. Seahorses have been observed in the marina, and it is possible that this man-made environment serves as an important refuge for the animals in which they are protected from fluctuations in habitat quality elsewhere in the estuary. In order to investigate this possibility, the Knysna Seahorse Status project was launched in February 2014. The project includes a population survey and investigations into the ecology of this particular species. This is expected to generate essential knowledge of the impact of artificial structures on habitat utilization by the seahorses.

By studying the Knysna seahorse population within the Thesen Islands Marina we aim to understand and establish:

-Behavioural and ecological aspects of the species

-The population abundance and distribution within the Thesen Islands Marina

-Habitat and holdfast use within the marina

This study allows us a very rare glimpse into the ability of H. capensis to adapt to anthropogenic impacts on their natural habitat. The Knysna seahorse is not only an iconic species for Knysna and South Africa – but for the world. This study will help generate valuable knowledge of the Knysna seahorse and the natural and anthropogenic factors that influence this species – knowledge that can contribute to seahorse conservation worldwide.

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