There appears to be little information too on the status of estuarine species, a serious gap in the overall conservation database. The estuaries of the Western and Eastern Cape play a vital role in providing a sanctuary to endemic species. Six flagship species include:
Knysna Seahorse (Hippocampus capensis):
This estuarine fish is endemic to South Africa, known only from the Knysna and Swartvlei estuaries of the southern Cape coast. It is considered the most endangered seahorse in the world (according to the IUCN Red Data lists). Its threatened status is due to habitat degradation in its extremely limited habitat and mass mortalities in the Swartvlei estuary, caused by artificial breaching of the estuary mouth.
Peringuey’s Leaf-toed Gecko (Cryptactities peringueyi):
This small gecko was rediscovered in 1992 after being ‘lost’ for 80 years. It is the only gecko in the world that lives in salt marshes, and is known only from the Kromme River estuary and a few sites near Port Elizabeth. As salt marshes disappear under bulldozers, so will this unique gecko.
White Steenbras (Lithognathus lithognathus):
The once abundant White Steenbras is now severely depleted – down to 5% of its previous biomass - through over-fishing (due to its spawning aggregations it was vulnerable to heavy fishing pressure and beach seine nets) and habitat degradation (it is estuary dependent for juvenile nurseries). Severe restrictions on fishing are now in place to save this valuable endemic.
Estuarine Pipefish (Syngnathus watermeyeri):
Another Eastern Cape endemic, this fish was known only from the Bushmans, Kariega and Kasuka estuaries, with the last known specimens in these estuaries collected in 1963. However, in 1996 a healthy population was discovered in the East Kleinemonde estuary, the only estuary where this species has again been found. The absence of the required fresh water pulses into the estuaries, in catchments where upstream impoundments have inadequate environmental flow allocations, is responsible for its precipitous decline.
Burrowing Prawn (Callianassa sp.):
Abundant in estuaries from Saldanha on the West coast to southern Mozambique, burrowing prawns are targeted by fishermen for bait. Nevertheless, their populations appear robust and they are more at risk from isolated events, such as salinity fluctuations and pollution.
Eelgrass (Zostera sp.):
Eelgrass, present in many South African estuaries, binds sediments, provides shelter for juveniles, and serves as a primary food producer. It is threatened by mismanaged catchments, pollution, and disturbance of estuaries. Eelgrass stands remain viable in smaller estuaries, but rehabilitation in larger systems in urgently needed.
Because of habitat degradation and increasing human pressures on estuaries, 4 South African estuarine fish species are listed on the IUCN Red Data List. These are Doublesash butterflyfish,Chaetdon marleyi, Knysna seahorse, Hippocampus capensis, St Lucia mullet, Liza luciae and Estuarine pipefish, Sygnathus watermeyeri, all of which are considered ‘critically endangered’.