Seahorses and sewerage – the delicate balance of the Knysna estuary

Posted by Scott Ramsay on 31 January 2012

Knsyna is famous not only for its indigenous forests, but also its estuary, which is the biggest – and most ecologically important – in the country. According to several scientific studies relating to birds, fish and plants, it ranks higher than all other estuaries in terms of its natural importance.

Incredibly, according to research supplied by SANParks, it hosts 43% of all of South Africa’s estuarine natural life – all the more incredible, because the Knysna estuary is just 1 800 hectares in size,  and is home to some rare, endemic species that aren’t found anywhere else in the world – including the Knysna seahorse.

This seahorse is found here as well as in the nearby Swartvlei. It is one of six seahorses found in South Africa, and is the only species in the world that is on the IUCN’s (International Union for Conservation of Nature) endangered list – largely because of encroachment on its natural habitat by urban and industrial development. Adults grow to a maximum of seven centimetres long, and somewhat bizarrely, it’s the males which give birth to the tiny young, carrying them in a special pouch until they are ready to be released.

The estuary is also very important to South Africa’s fishing industry – it contributes 22% of the nation’s estuarine value to commercial fishing, and is the country’s most important nursery to line fish like red stumpnose, cob, white steenbras and spotted grunter. As a source of food to local people, several hundred people rely on it for putting foods on their plate every night.

Then, of course, there are the tourists who flock here during summer and school holidays. According to marine ranger Shamley Titus – who took me around the estuary on the SANParks patrol boat – there can be as many as 500 boats on the estuary at any one time during summer, ‘That’s a lot of boats for what is quite a small area,’ says Shamley.

Shamley took me down to the famous Knysna Heads, where the waters of the estuary empty into the ocean. In times past, these iconic rock promontories have claimed many a yacht and ship, as the vessels need to pass through what is a relatively narrow gap to escape the rough ocean, and find sanctuary in the calm waters of the lagoon.

Shamley told me how the lagoon is visited by several kinds of sharks, especially ragged tooth sharks, but also whales, especially southern right whales.

But the Knysna estuary is heavily developed – houses, restaurants and marinas all crowd the sensitive marsh areas, which are so important for breeding fish and birds. And of course, there’s Thesen Island, which is a serious eyesore, built right in the middle of the lagoon. However, the development is now under strict control, and SANParks have a tough job trying to conserve one of South Africa’s most precious waterways.

Recently, the town’s sewerage works sprung a leak, and thousands of litres of contaminated water poured into the estuary. The ecosystem took a hammering as E. coli levels rocketed. The water works have since been upgraded, and this sort of thing shouldn’t happen again, but who knows. It’s just one example of the challenges involved in managing a national park which lies in one of South Africa’s most popular tourist towns.

For more, go to and Thanks again to my sponsors for making it all possible. CapeNature, South African National Parks, Ezemvelo KZN Wildlife, Eastern Cape Parks, iSimangaliso Wetland ParkFord, Total, Evosat, Conqueror TrailersVodacom, Digicape, Lacie, Frontrunner, Safari Centre Cape TownK-Way, EeziAwn, National Luna, Nokia , Goodyear, Global Fleet Sales, HetznerClearstream Consulting and Escape Gear.

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