South Africa
Information sheet for the site designated to the
List of Wetlands of International Importance
in terms of the
Convention on Wetlands of International Importance
especially as Waterfowl Habitat
COUNTRY
South Africa
DATE OF COMPILATION
Originally completed: January 1990
Updated: August 1995REFERENCE NUMBER
Not yet available
COMPILER
Originally compiled by:
Dr. RM Randall
National Parks Board
P O Box 774
GEORGE
6530
South AfricaTEL: (04455) 1302
Updated by:
Dr. RM Randall
IA Russell
National Parks Board
P O Box 176
SEDGEFIELD
6573
South AfricaNAME OF WETLAND
Wilderness Lakes
DATE OF RAMSAR DESIGNATION
28 June 1991
GEOGRAPHICAL CO-ORDINATES
33º 59' S
22º 40' EGENERAL LOCATION
The Wilderness Lakes are located 14 km east of George and 30 km west of Knysna on the south eastern Cape coast.
George : 14 km West
Sedgefield : 4 km East
Knysna : 30 km EastNorth boundary : Approximately, railway line on edge of floodplain and lower reaches of Duiwe River
South boundary : Edge of the floodplain (c.5 m contour)
East boundary : Swartvlei Lake
West boundary : West end of the Serpentine channel where it joins the Touw River.AREA (ha)
1300 ha
9.1 Boundary integrity
There have been no changes in the boundaries. There is a need to enlarge the area: particularly the catchment and those part of the flood plain in private ownership, where development would negatively impact the functioning of the system and the biota.
WETLAND TYPE
F (Estuarine waters)
J (Coastal brackish/saline lagoons)
Q (Saline/brackish lakes/marshes: permanent)ALTITUDE
MIN: 1 m
MAX: 200 mOVERVIEW OF SITE
The Wilderness Lakes comprise a series of interconnected coastal lakes, parallel to the coastline, that are linked to an estuary and lagoon that opens periodically to the sea. Seawards of the wetland is an old consolidated dune which is vegetated with coastal fynbos and dune thicket, while inland of the wetland is a steep slope rising to a plateau. The slope is densely vegetated with coastal forest and bush.
PHYSICAL FEATURES
13.1 Geology and geomorphology
The lakes are situated on sands and alluvium of Pleistocene and Recent age against a back-drop of steep Tertiary-age sea cliffs on the north side and Pleistocene-age fossil dunes on the south side.
13.2 Origins
The system in its present form is thought to have formed about 7000 years ago. Between 45000 and 10000 years ago, during the periods of glaciation in the northern hemisphere, the sea alternately covered the entire area of the Wilderness Lakes to the base of the cliffs of the Tertiary-age uplands during warm periods, and then receded with the formation of the northern ice-caps. Then, with the end of the northern hemisphere glaciation, strong coastal winds associated with increased land temperatures led to the formation of coastal dunes. The dunes blocked the estuaries which resulted in basins forming inland of the dunes, and these lakes or barrier lagoons occasionally broke through to the sea. The Wilderness Lakes have been formed by the segmentation of an earlier lagoon.
13.3 Hydrology
The hydrology of the lakes is dominated by the flooding of the Touw and Duiwe Rivers when the mouth of the estuary is closed and by tidal influence when the mouth is open. The upper lakes are filled by reverse flow, where water from the Touw and to a lesser extent the Duiwe River flows back via the lower lakes and channels. This is especially the case when the mouth of the estuary is closed, and the process serves to ameliorate the effects of floods in the Touw River estuary. The hight of sea sand sill at the mouth of the estuary has to be artificially maintained to prevent and for the same reason the mouth has to be opened. The estuary closes naturally under the influence of longshore drift and deposition of marine sediments in the mouth.
13.4 Soil type and chemistry
Most of the floodplain is covered in a dark alluvium which is rich in organic matter. The dunes and higher lying areas have a loose sandy soil with a low humus content.
13.5 Water quality
Surface temperatures range between 10 and 27C. Salinity in the lakes varies between 2 and 16 ppt, with the highest values in Rondevlei, whereas in the estuary it varies between 0 and 25 ppt. The variability in salinity depends on floods and whether the mouth is open. Approximate average values for parameters measured are as follows: salinity = 10 ppt, dissolved oxygen = 7 mg/l and pH = 8. Nitrate and phosphate levels are well below those associated with eutrophication. Inflowing streams are the most important as sources of both inorganic nitrogen and phosphorus. Occasional elevated levels of soluble reactive phosphorus appeared to be associated with large numbers of water birds. Chlorophyll values follow the pattern of that for phosphate, occasionally reaching values as high as 37x10S0-6T g/l but decreasing to average levels (3x10S0-6T g/l) soon after, unlike in true eutrophic waters.
13.6 Depth, fluctuations and permanence
The maximum depths of the different waterbodies are as follows: Touw River = 3 m, Eilandvlei = 4 m, Langvlei = 3 m and Rondevlei = 4 m (See Figure 2). The waterbodies are permanent and fluctuations in levels are within narrow limits. The flood levels for 5 and 100 year floods for the different parts of the system are as follows: Touw River 1.7 m and 3.15 m, Eilandvlei 1.2 m and 1.85 m, and Langvlei/Rondevlei 0.5 m and 1.35 m respectively.
13.7 Tidal variations
Highest Astronomical Tide 2,31
Lowest Astronomical Tide 0,11
Mean High Water Springs 1,96
Mean Low Water Springs 0,36
Mean High Water Neaps 1,43
Mean Low Water Neaps 0,90
Mean Level 1,1613.8 Catchment area
The catchment areas of the two rivers are as follows: Touw River = 101 km2 and Duiwe River = 34 km2.
13.9 Downstream area
The Indian Ocean, but sometimes it is closed to the sea.
13.10 Climate
The lowest average temperature is 10,0 C and the highest average temperature is 22,9 C. The relative humidity varies from 41% - 93%. The average rainfall is 770 mm and is not in a specific season.
ECOLOGICAL FEATURES
About 320 species of plants have been identified from the Wilderness Lakes and immediate surroundings. Three easily identifiable vegetation components exist at the Wilderness lakes, and a fourth above the 5 m contour above mean sea level (a.m.s.l.) outside the area to the north. These four components are:
- aquatic,
- semi-aquatic,
- coastal fynbos, and
- forest.
LAND TENURE
The National Parks Board manages the entire wetland on behalf of the state according to the provisions of the National Parks Act.
The surrounding areas are privately owned. In the catchments other state land is declared State Forest and administered by the Department of Water Affairs and Forestry.
15.1 Legal status
The entire area falls within the Wilderness National Park which was proclaimed in April 1983. The contiguous Lakes Nature Reserve, comprising Rondevlei and surrounding land (212 ha), was added in 1992. A conceptual master plan was devised in 1985 and is currently being updated and substantially enlarged.
The have been no changes in the legal status. The National Parks Board manages the entire wetland on behalf of the state according to the provisions of the National Parks Act. Surrounding areas to the North, South and West are privately owned, whereas areas to the East (Swartvlei system) form portion of the Wilderness National Park managed by the National Parks Board. In the catchments other state land is declared State Forest and administered by the Department of Water Affairs and Forestry.
CONSERVATION MEASURES TAKEN
The control of water levels is probably the most significant management practice in terms of impact on the ecology. Management actions in this field are based on recommendations contained in reports incorporating a hydrodynamic model of the entire Touw River system.
Flood control
The Touw River mouth periodically closes and a sill then gradually builds up by deposition of sand with a marine origin transported by longshore drift. If left to function naturally water levels rise prior to breaking through the sill and this causes flooding of residential properties that were unwisely built in low-lying areas in the mouth area. (No further building in low-lying areas is permitted). In the interests of the ecology of the system water levels should be allowed to approximate the natural regime as closely as possible and extremes should not be dampened. Unfortunately the flooding of residential properties precludes this, so artificial manipulation of the mouth is necessary.
The small catchment of the Touw River results in peak discharge after about seven hours giving little reaction time in the event of major downpours. Through measurements and a hydrodynamic model, a 1:50 year flood was simulated which revealed that by keeping the sill at about 2.1 m a.m.s.l. flooding of these properties could be prevented. Consequently present policy is to skim the sill to a height of 2.1 m a.m.s.l. with a tractor (Figure 2).
Dredging
Minor floods in the Touw River system are accommodated by reverse flow into the lakes system via the Serpentine. This is also the source of most of the water in the lakes. For both of these reasons the connecting channels between the lakes are of considerable significance and are therefore dredged to facilitate flow, but not so deep as to cause major dry-downs. The connections that are dredged are the Eilandvlei/Langvlei and Langvlei/Rondevlei channels.
An added reason for the maintenance of the channels is to facilitate the movements of fish, notably those with a marine phase in their lives.
Clearing of macrophytes
The connecting channels become overgrown with both submerged and emergent macrophytes, which in turn exacerbates the siltation and flooding problems. Consequently it is management policy to cut macrophytes and clear them from the two channels.
Sluice operation
The deepening and clearing of interconnecting channels increases inflow but also increases outflow when the mouth is open, thereby causing the system to drain. The upper lake levels are then determined by the levels of the interconnecting channels, and to prevent excessive draining a sluice was installed on the Serpentine. The theory behind the sluice operation is that it is kept open when the mouth is closed and is shut when the mouth is open. The sluice could seriously restrict recruitment of juvenile fish when it is shut so allowance is made some water to pass through, thereby enabling fish to move upstream.
Invasive aliens
Over 35 alien (i.e. exotic) plant species have been identified in the WNP and immediate surroundings. The great majority are terrestrial plants occurring on the floodplain and fynbos areas.
Some (e.g. rooikrans Acacia cyclops, sesbania Sesbania punicca, and stinkbean Albizia lophantha) are invasive woody species that pose a threat to the indigenous flora. These plants are controlled by mechanical means at present and there is also the possibility of using biological control.
16.1 Management plan
Compiled
A conceptual master plan was devised in 1985. An updated and enlarged, though incomplete, draft was produced in May 1993. Submissions are required detailing some management procedures and communication services. The processes of public discussion and acceptance by the Board of Curators of the National Parks Board have still to be undertaken.
Several of the management activities conducted elsewhere in the system indirectly have an impact on the Wilderness lakes area. An example of this is the manipulation of water levels that is undertaken at the estuary mouth.
National Park (IUCN Category II)
CONSERVATION MEASURES PROPOSED BUT NOT YET IMPLEMENTED
Virtually all conservation measures proposed have been implemented and those suggested below will depend upon the results of research projects to determine their desirability and the extent of action that should be taken.
Water levels:
The continued manipulation of water levels is inevitable using the present approach. Based on experience gained over several years of operation there is evidence to indicate that the sluice has not functioned as expected and may in fact not be necessary, except under extreme circumstances. In view of its likely detrimental impact on fish migration and recruitment to the upper lakes it is important that the need for the sluice be reassessed. In the interim its operation should cease and the situation should be monitored.
There is an increasing realization that extremes and disturbances in ecological systems are desirable as part of the natural process. Presently there is a tendency in the WNP to manage the system to damp extremes in water levels. It is no longer possible to permit high water levels to develop but occasional dry-down may be ecologically desirable. This requires research and careful monitoring should it be implemented.
Whenever possible, artificial opening of the mouth should be restricted to the spring and summer months when maximum recruitment of fish stocks from the sea occurs. An added benefit of this timing is that in the mouth-open phase the upper floodplain drains, exposing sand banks on which the summer migrant waders feed.
Alien organisms:
The removal of alien plants must be continued and expanded to include more species. Concern has been expressed about the invasion by alien grass species, such as paspalum Paspalum vaginatum and kikuyu Pennisetum clandestinum, on the sand- and mud-flats which are alleged to be rendered unsuitable for wading birds. The situation needs to be researched, and if desirable, measures devised and implemented for the removal of these grasses.
Enlargement of area
There is a dire need to enlarge the area, particularly those parts of the flood plain in private ownership, and that are being cultivated.
CURRENT LAND USE
Surroundings and catchment
In the area immediately surrounding the Wilderness lakes the dominant form of land use is agriculture. This takes the form of low intensity cultivation on a few small-holdings and low intensity stock farming using cattle for meat production and dairying. The next most important forms of land use are exotic plantations of pines Pinus pinaster grown for timber. There is also a rapidly increasing number of cottages on small-holdings, some are occupied permanently and others only in the summer holiday season.
In a wider surrounding area the land use is basically similar except that there are several holiday resorts and more residential properties.
The constrains listed below apply specifically to the Wilderness lake area but several are also applicable to the wider WNP.
18.1 Resource utilization
Consumptive utilization
Fishing with hook and line is permitted in Eilandvlei and portions of the Serpentine channel. Fishing is undertaken primarily by local residents and no charge is levied. The quantity of fish removed is unknown though is unlikely to be substantial. Sea Fisheries regulations with respect to size and bag limits are enforced.
Non-consumptive utilization
Most forms of boating are permitted on Eilandvlei, with canoeing on the Serpentine channel. Boating is undertaken by both local residents and seasonal visitors, with higher utilization possibly by the latter group. An entrance fee is payable for access to Eilandvlei during peak holiday seasons, and gross income from this source amounted to c. R 24 000 in 1993. Boat numbers on Eilandsvlei are not currently limited. Regulations pertaining to the safe handeling of boats are inforced.
Swimming and picnicking is permitted in demarcated areas at Eilandvlei. Returns associated with these activities are included in assessments for boating described above.
Hiking/walking trails have been laid out in the Touw River/Serpentine area on the floodplain, in the forest above Eilandvlei and in the fynbos area east of Rondevlei. Bird hides have been constructed at Rondevlei and Langvlei, and there are numerous points on the water between the Touw River estuary and Langvlei for birding. Trails and hides are utilised free of charge by both local residents and seasonal visitors.
Resorts, NPB and private, providing camping and accomodation facilities are locate on Eilandvlei and the Touw River estuary/ Serpentine. The two resorts operated by National Parks Board are utilised primarily by seasonal visitors, and gross income in 1993 amounted to c. R 1 200 000.
DISTURBANCES AND THREATS INCLUDING CHANGES IN LAND USE AND MAJOR DEVELOPMENT PROJECTS
AGRICULTURE:
Abstraction:
The impoundment and abstraction of waters in the catchment, and hence reduction in the amount of fresh water entering the lakes poses the single greatest threat. Present abstraction is approximately 30% MAR (forestry = 3.7 x 10 6. m3, +/-15% MAR; agriculture = 2.9 x 106 m3, = +/- 12% MAR; domestic = 0.5 x 106 m3, = +/-2% MAR) which is likely to increase to 40% due to envisaged future developments.
Eutrophication:
The catchment of the Duiwe River which enters the eastern end of Eilandvlei near Langvlei is highly developed agriculturally and could be an important source of nitrate and phosphate that could lead to eutrophication. Until recently eutrophic conditions have been of short duration, but increased inputs from the Duiwe River catchment could cause longer-term eutrophic conditions with consequent water quality problems.
Developed properties surrounding the wetland utilize soak-away sewage disposal systems, and hence are a likely source of nutrients. Installation of a reticulated sewage system at Hoekwil in the Duiwe River catchment necessitated the routing of a sewage pipeline through the Serpentine channel. Failure of this pipeline would result in the inflow of substantial volumes of raw sewage into the wetland.
Suspensoids:
The Duiwe River, and to a lesser extent the Town River, carry high suspensoids loads during floods. The problem is a reflection of poor farming practices in the catchment and the degree of deforestation. Siltation of the channels and lakes, results in shallowing and a reduction in water clarity.
Pesticides:
Past studies of the levels of chlorinated hydrocarbon insecticides (DDT and its metabolites and Dieldrin) and polychlorinated biphenyls (PCBs) in African marsh harrier Circus ranivorus eggs have indicated than there is a source of these compounds.
Deforestation:
Deforestation in surrounding areas to provide agricultural land is leading to increasing fragmentation of the natural vegetation and thus indirectly to the fauna.
Alien invasive
Over 35 alien plant species have been identified in the Wilderness National Park and immediate surroundings. The majority of these are terrestrial species with some (eg. black wattle Acacia meransii, rooikrans Acacia cyclops, sesbania Sesbania punicca, stinkbean Albizia lopantha) posing a threat to the indigenous flora. Concerns have been expressed about the invasion of alien grass species, such as Paspalum vaginatum and kikuyu Pennisetum clandestinum on the sand- and mud-flats. The water fern Azolla filiculoides has recently become established on Eiland vlei, where dense mats form around the margins of the lake. Spread of azolla to Langvlei and Rondevlei has occurred though infestation levels are currently not high.
DEVELOPMENTS:
No further development on the floodplain below the 1:50 year and ideally 1:100 year floodline should occur. This relates to structures, notably permanent structures, but exceptions could be made for structures such as bird hides.
No further roads should be constructed on the floodplain and some existing roads could be deproclaimed to reduce traffic.
No further bridges across connecting channels should be permitted nor should existing ones be widened. Bridges should only be modified (e.g. changing the height of the bottom of the culvert) if research has indicated that changes are desirable.
The natural beauty of the area coupled with its uniqueness make it very attractive as a holiday destination and retirement centre. A result is escalating prices of real estate which in turn is making it increasingly difficult to acquire additional land for incorporation into the WNP.
Private housing developments and facilities for tourism are posing an increasing threat to the aesthetic beauty of the lakes and surroundings. This has led to calls for vetting the design of new structures to ensure they blend in.
Activities:
In the development of walking/hiking trails caution should be exercised to ensure that the siting of the trail is not ecologically and aesthetically detrimental.
Groups sizes and general carrying capacity of trails will have to be worked out with appropriate research. It may prove necessary to limit use of trails in certain areas or at certain times.
The ecological implications of a proposed canoe trail through Langvlei and Rondevlei should be thoroughly investigated before it is implemented. Of particular concern is the impact of disturbance on waterbirds, especially when they are breeding. It may be found desirable to limit activity to certain areas and to certain periods if the canoe trail is to proceed.
AQUACULTURE:
Alien organisms:
Alien organisms enter the system when they escape from farm dams or when dams break during floods. The Mozambique tilapia Oreochromes mossambicus, which is widespread in the wetland, is thought to have been artificially introduced. The mosquitofish Gambusia affinis has recently (1994) been recorded in Rondevlei. There is concern that aquaculture on private land using the alien freshwater crayfish or marron Cherax tenuimanus could result in this species becoming established in the Wilderness lakes.
HYDROLOGICAL AND BIOPHYSICAL VALUES
Not available.
SOCIAL AND CULTURAL VALUES
Current
Principal social values are those of ecotourism, outdoor recreation, education, scientific research and flood control - presently none are significantly detrimental to ecological processes. In the immediate surroundings residential, retirement and holiday housing and small-scale agriculture - increasingly detrimental to aesthetic beauty, natural vegetation and fauna.
History
The history of the area is poorly documented and scattered in various narratives, often as anecdotal accounts. Prior to the arrival of the first westerners the area was inhabited by Khoisan peoples, some of whom possibly had cattle. It is known that groups of Khoi at Mossel Bay (460 km west of the Lakes) had large herds of cattle and sheep. In the surrounding areas there were groups of San hunter-gatherers.
The first groups of people of Negroid descent appear to have entered the area in about 1802.
The fist westerners to see the area were Portuguese mariners on exploratory voyages and the first of these was Dias in 1488. They laded on the coast near the Lakes but did not venture inland. About 200 years later staff of the Dutch East India Company (VOC), carried out exploratory visits but only some 100 years later were outposts established, primarily for harvesting the indigenous woods. On account of inaccessibility the area remained largely isolated even into the 1800's when there was a gradual increase in settlement, primarily for the purposes of farming. Following the completion of the road in 1883 the Wilderness Lakes became more accessible. A railway line was completed in 1928 and a coastal tarred road was built in 1948.
The initial settlers were wood cutters, followed by farmers (cattle farmers and limited cultivation) and latterly the area has become as a holiday resort and retirement area.
Archaeology:
There are no archaeological sites known on the floodplain of the Wilderness lakes area, but there are two sites in the forest above the lakes. These are the Oakhurst shelter and the Glentyre shelter about 400 m from Eilandvlei. The sites are of similar age, extending from about 12 000 years B.P. to very recent.
Remains of mammals like hippopotamus Hippopotamus amphibius, buffalo Syncerus caffer, bushpig Potamochoerus porcus and zebra Equus sp. amongst others were excavated at the Glentyre shelter.
There are also so called "Strandloper middens" in the area. These are essentially piles of mulluscs, mostly bivalves, that accumulated where coastal Khoi people worked food collected in the intertidal zone of the seashore. The upper date of these middens is about A.C. 1 800.
Palaeontology:
There are no palaeotological deposits known within the area of the Wilderness lakes.
NOTEWORTHY FAUNA
For convenience the fauna is divided into two broad categories, viz. aquatic and terrestrial.
AQUATIC:
The aquatic component has received the bulk of the research effort and is better documented and understood.
Invertebrates:
The zooplankton fauna is dominated by typical estuarine species that rely on a marine link and higher salinities for their existence. Copepods (eg. Acartia natalensis and Pseudodiaptomus hessei) and larvae of the bivalve Musculus virgiliae are the dominant species in the zooplankton. Freshwater organisms (eg. Cladocera) are washed down into the system following rainfall in the catchment area and marine species enter the estuary when the mouth is open to the sea. Measurements of standing crop in daytime showed that Langvlei had the greatest biomass, followed by Rondevlei and Eilandvlei.
Macro-invertebrates of the lakes are essentially estuarine and require a marine link. Dominant species are amphipods (Corophium triaenonyx, Grandidierella lignorum and Melita zeylanica), isopods (Exosphaeroma hylecoetes, Cyathura estuaria), bivalve (Musculus virgiliae), polychaete (Ficopomatus enigmatica), crab (Hymenosoma orbiculare) and prawn (Callianassa kraussi). Chironomidae are the most important freshwater group. All of these invertebrates feed predominantly on detritus, consequently submerged macrophytes are vital to them as a source of detritus and for some as attachment sites.
Fish:
The fish fauna is dominated by euryhaline marine migratory species and the diversity is low (32 spp). The diversity is greatest near the Touw River mouth (23 spp) and decreases towards Rondevlei (12 spp). With nine exceptions fish species occurring in the Wilderness Lakes System have a marine phase in their life cycle. The most abundant of these exceptions are estuarine round herring Gilchristella aesturius, Cape silverside Atherina breviceps, both estuarine species, and Mozambique tilapia Oreochromis mossambicus, an introduced freshwater cichlid. The euryhaline marine species enter the estuary as juveniles. They migrate up into the lakes, which function as nursery areas, and mature, before they return to the sea again to spawn. The most abundant examples of this group are mullets (eg. Liza richardsonii, L. dumerilii, Mugil cephalus), sparids (Rhabdosargus holubi, Lithognathus lithognathus, Pomadasys commersonnii) and soles (Heteromycteris capensis).
Of the dominant fish fauna mullets and Mozambique tilapia are detritivores; estuarine round-herring, Cape silverside and white steenbras L. lithognathus feed on invertebrates; Cape stumpnose R. holubi feeds on invertebrates and aquatic plants; leervis Lichia amia is the only fish predator.
Most juvenile fish recruitment occurs during the austral summer. The extent of the recruitment was demonstrated in February 1984 during a mouth-open phase when 52000 fish were estimated to have migrated up the Serpentine to the lakes.
Avifauna:
Some 57 species of "waterfowl" (defined as any of the taxa Accipitriformes, Podicipedidae, Pelecanidae, Phalacrocoracidae, Ciconiiformes, Anatidae, Falconiformes, Sternidae, Charadriidae) or 72 species of "waterbirds" (defined by Boshoff & Palmer 1990 as non-passerines relying entirely on permanently or temporally inundated or semi-inundated areas) have been identified at the Wilderness lakes (Table 1).
The number of waterfowl fluctuates considerably from year to year on account of water conditions (eg. some species such as Cape shoveller Anas smithii and the other dabbling ducks prefer low water levels) and from season to season on account of migration (there is an influx of Palaearctic migrants in summer and local migrants at various times through the year). From counts in 1983 and 1984 maximum numbers counted and average numbers, which underestimate the migrants, yielded figures of about 23 000 and 10 500 waterbirds respectively.
There are two species of waterfowl occurring at the Wilderness lakes that are classified as Rare. One of these is the little bittern Ixobrychus minutus payesii which appears to be a resident as immatures have been seen at Rondevlei and these are records from all months of the year. There are thought to be less than 100 breeding pairs in South Africa.
The second Rare species is the Caspian tern Hydroprogne caspia that occurs as an irregular non-breeding visitor with less than five together at any one time. There are thought to be about 150 breeding pairs in South Africa.
There are significantly large populations of two duck species. At times 5 % of the total population of Cape shovellers and 3 % of the South African population of Yellowbilled duck Anas undulata occur at the Wilderness lakes. The Cape shoveller is a Southern African endemic that is regarded as potentially the most vulnerable of the waterfowl species on account of its restricted range, small population and specialized habitat and feeding requirements.
The lakes appear to function as a valuable refuge out of the breeding season for some species of waterfowl (eg. blacknecked grebe Podiceps nigricollis, darter Anhinga melanogaster) that breed inland at annual pans and small waterbodies which tend to dry up periodically. There is also evidence to suggest that the lakes are used by several species of the Anseriformes (eg. spurwinged goose Plectropterus gambensis, Egyptian goose Alopochen aegypticus, yellowbilled duck, Southern Pochard Netta erythropthalma) as a stopover point on their moult migration.
TERRESTRIAL
Comparatively little research has been undertaken on the terrestrial fauna.
Invertebrates:
Representatives of nine of the ten families of butterflies (Lepidoptera) that occur in Southern Africa have been identified on the floodplains and immediate surroundings. In all, 48 species have been identified from the area. None of these is recognized as Rare, Threatened of Endangered.
Avifauna:
Apart from waterbirds about 170 species of birds have been recorded for the floodplain and the surrounding area. One of these, the grass owl Tyto capensis, is known to breed on the floodplain. The species is decreasing in number and the southern Cape population is becoming increasingly isolated. The status of the species is described as "Indeterminate" as there is insufficient information available, but it will probably rank as Rare.
Mammals:
Bushbuck Tragelaphus scriptus still occur in the forest on the slopes just north of the lakes and bontebok Damaliscus dorcas dorcas have been introduced to the coastal fynbos near Rondevlei, but otherwise there are no large mammals in the area. A surprising variety of small carnivores are present: caracal Caracal caracal, large-spotted genet Genetta tigrina, white-tailed mongoose Ichneumia albicauda, large grey mongoose Herpestes ichneumon, Cape grey mongoose H. pulverulentus, water mongoose Atilax paludinosus, Cape clawless otter Aonyx capensis. Limited surveys of small mammals showed that there are vlei rats Otomys irroratus, striped mice Rhabdomys pumilio, red musk shrews Crocidura flavescens and forest shrews Myosorex varius, on the floodplain. Cape dune molerats Bathyergus suillus occur on the coastal fynbos where they are regarded as important in maintaining the plant communities through their disturbance and activity.
22.1 Species counts
What species groups counted
All waterbids.
Frequency of counts
Quarterly counts (January, April, July, October) of eight abundant species (great crested grebe Podicepts cristatus, reed cormorant Phalacrorax africanus, darter Anhinga melangaster, grey heron Ardea cinerea, Cape shoveler Anas smithii, yellowbilled duck Anas undulata, Cape teal Anas capensis and redknobbed coot Fulica cristata) on all waterbodies in the Wilderness National Park.
Biannual counts (January, July) of all waterbirds in the Wilderness National Park.
Methods used
All counts are undertaken from a boat following a fixed route.
Date of last count
July 1995
Results
Some 11 000 birds of 45 species were counted. Although coots were the most numerous species, a spectrum of ducks and piscivores formed important components of the waterbird fauna. The Wilderness Lakes continue to be significant refuges for several species (eg great crested grebes). The biomass of waterbirds (1992 to 1995) was highest on Langvlei (10.03 kg ha-1), followed by Rondevlei (6.78 kg ha-1), and Eilandvlei (6.57 kg ha-1).
Trends
The mean biomass for the period 1992 to 1995 was substantially higher that recorded during a previous study from 1980 to 1984. Seasonal changes occur in the abundances of several species: reed cormorant, darter, grey heron and redknobbed coot are more abundant in the winter months, and Cape shoveller in the summer months.
NOTEWORTHY FLORA
The vegetation (aquatic and terrestrial) of the lakes and the surrounding area has been studied in some depth and there are a number of publications including annotated checklists, vegetation maps, biomass and production estimates.
About 320 species of plants have been identified from the Wilderness Lakes and immediate surroundings. Three easily identifiable vegetation components exist at the Wilderness lakes, and a fourth above the 5 m contour a.m.s.l. on the northern side.
23.1 Aquatic:
The surface waters of the Wilderness lakes have clear open water in the central areas and fringing beds of macrophytes in the littoral zone. For convenience the macrophytes can be separated into submerged and emergent units.
The dominant submerged macrophytes of the Wilderness lakes are Ruppia cirrhosa, Potamogeton pectinatus and Characeae (e.g. Chara globularis, Lamprothamunium papulosum). The biomass of submerged macrophytes varies greatly from year to year; for example virtually the entire lake bottom of Langvlei was covered by Characeae in 1975 but this died off almost completely by 1978 following a dinoflagellate bloom which dramatically reduced water clarity. The submerged macrophytes carry most of the zoobenthos and are vital to the system on account of their organic matter production, via particulate-feeding invertebrates, to the detritus food web. Furthermore the submerged macrophytes are important attachment sites for suspension-feeding invertebrates.
The dominant species of emergent macrophytes are reeds Phragmites australis, bulrushes Typha latifolia and sedges Scirpus litoralis. Reeds and bulrushes undergo seasonal fluctuations in biomass, but there is comparatively little year to year change. Emergent macrophytes produce over 80 % of the organic matter and, although only a portion of this enters the lakes as detritus, they are important to Macro-invertebrates feeding on detritus.
23.2 Semi-aquatic:
This vegetation unit occurs on the low-lying areas of the floodplain adjacent to the lakes and channels, where it is subject to inundation at high water levels. Dominant species are rushes Juncus kraussii and sedges Cyperaceae. In slightly higher-lying areas the rushes and sedges are bordered by buffalo grass Stenotaphrum secundatum. Plants growing in this area are tolerant of short-term fluctuations in water levels, but sensitive to long-term alterations in water supply.
23.3 Coastal fynbos: (coastal macchia)
Coastal fynbos is confined to the slightly higher-lying areas bordering the floodplain. This vegetation unit grows on well-drained sandy soils and is regarded as a variant of dune fynbos. Relative to other fynbos types it contains a strong component of shrubs and trees which indicates that fires do not occur regularly. Dominant shrubs are Metalasia muricata, Passerina spp. and Rhus spp., and there is a large number and variety of fynbos annual herbs.
A mixture of coastal fynbos and dune forest is present on the old dunes to the south of the lakes.
23.4 Forest:
Evergreen forest with a closed canopy occurs immediately to the north of the lakes on the south-facing slopes of Tertiary-age sea cliffs and at places extend to within 300 m of Langvlei. These forests have a very high species diversity of woody plants in comparison with other forest types in the area, and also more creepers, geophytes, herbs and grass-like plants but fewer epiphytes and ferns.
There are as yet no recognized Rare, Threatened of Endangered plant species in the area, but there are some endemics in the coastal fynbos component that have very specialized habitat requirements. These include Satyrium princeps, Gladiolus vaginatus and two species that remain to be described, viz. Silene sp. nov. and Herschelianthe sp. nov. Further research on these plants is required but is likely that most, if not all of them, will be found to qualify for one of the three categories.
SCIENTIFIC RESEARCH FACILITIES
The National Parks Board has an aquatic biologist stationed at the Regional Centre of the Scientific Services Section at Rondevlei whose main responsibility is conducting the monitoring programme for the Wilderness National Park. A further responsibility is to undertake research relevant to the management of the Wilderness National Park.
The Rondevlei Regional Centre has laboratories where water quality analyses are undertaken, as well as general laboratories, offices, computer facilities (including GIS). Vehicles, boats and sampling gear are also located at the centre. A university researcher is also working there while undertaking a study of rivers and streams in the catchment.
24.1 Projects in progress
- Sedimentation in the lower estuary in relation to management activities.
- Reassessment of the impact of the sluice, other constrictions and general management on fish populations.
- Basic inventories of such faunal components as amphibians, reptiles and small mammals.
- Investigate disturbance of waterbirds by boating activities, notably canoeing.
Researcher: Y.E. van Wijk
Duration: 5 years Title: Monitoring water-bird abundances in the lakes and estuaries of the Wilderness National Park.
Researcher: I.A. Russel
Duration: On-going Title: Monitoring water quality in the lakes, rivers and estuaries of the Wilderness National Park and Knysna estuary.
Researcher: I.A. Russel
Duration: On-going Title: The standing biomass of submerged aquatic plants in the littoral zone of the saline waterbodies of the Wilderness National Park.
Researcher: I.A. Russel
Duration: On-going Title: Monitoring fish communities in the saline lakes and estuaries of the Wilderness National Park.
Researcher: I.A. Russel
Duration: On-going Title: Effects of land-use changes on the rivers of the Wilderness lakes.
Researcher: E.S. Filmalter
Supervisor: J.H. O'Keeffe
Duration: 3 years24.2 Projects just completed
Title: Application of the estuarine health index to South African estuaries.
Researcher: T.D. Harrison
Duration: 4 years Title: Geomorphic evolution of the Wilderness dune cordons.
Researcher: W.K. Illenberger and I.C. Rust
Duration: 2 years Title: Wilderness, Swartvlei and Groenvlei catchment areas: Water management Strategy.
Researcher: GF & J Inc.
Duration: 2 years24.3 New findings
Salinities in Langvlei and Rondevlei continued to show downward trends (annual average from 1991 to 1994 in g kg-1 : Langvlei = 10.5, 10.0, 8.6, 7.8; Rondevlei = 13.9, 14.1, 13.4, 12.6), with average salinity in Eilandvlei during 1994 (5.7 g kg -1) also being lower than in previous years. In contrast, average salinity in the Touw River continued to show an upward trend (annual average from 1991 to 1994 in g kg-1 = 9.2, 9.9, 13.6, 16.4) as a consequence of increasing duration of tidal conditions. Dissolved oxygen concentrations were generally above 7 mg l-1 though low concentrations (<6 mg 1-1) were periodically recorded in most waterbodies for short August 1994, resulted in the input of large concentrations of sediments into the lake systems, evidenced solids, increases in turbidity and declines in secchi disk readings.
Increases in the above ground biomass of aquatic plants was found to have occurred in all waterbodies with the exception of Eilandvlei, where a significant decline was recorded. The possible shading effect of the exotic fern Azolla sp. on aquatic plants in Eilandvlei remains a concern.
The recruitment of most marine fish into the Wilderness lakes is unlikely to have been negatively affected by the recorded fluctuations in salinity of turbidity. Recent senescence of macrophytes, however, may have increased exposure of recruiting phytophyllic species to piscivorous birds and fish.
The Touw and Hoëkraal rivers were found to have retained more than 60% of the natural vegetation compared to less than 50% for the Karatara and Wolwe rivers, and less than 40% for the Diep and Duiwe rivers. Forestry consumes the highest fraction of water resources in all except the Diep River. The Touw River is the least impacted of the Wilderness catchments with total abstraction accounting for less than 15% MAR.
Brief investigations of water quality, fish community diversity and aesthetic conditions of the Touw River estuary were undertaken with the objective of applying the Estuarine Health Index. Water quality was considered acceptable for aquatic life. Aesthetic condition was considered to be moderate due to shoreline development. Eighteen fish species were collected. Overall, the system was regarded as being in moderately good condition, with a composite score of 7 out of a possible 9.
24.4 Proposed new projects
Undertake an assessment of long-term changes in the distribution of emergent aquatic plant communities in the Wilderness lakes.
CONSERVATION EDUCATION
The area is suitable for environment education programmes and low-key programmes during peak tourist periods are already in progress. These take the form of guided tours on foot by a fully qualified Information Officer of the National Parks Board.
There is a passive education programme in the form of displays, labelled plant samples, etc. Brochures incorporating maps and depicting the zoning are available.
Present facilities are inadequate for environmental education programmes but there are plans to establish an information centre in an old building which will be properly renovated. This will ensure continuity, more comprehensive displays and better information. Above all, it will then be possible to run environmental education programmes in situ.
The majority of conservation/ management staff of the National Parks Board responsible for law enforcement are required to have bachelor degrees, and preferably post graduate degrees. They are expected to perform the role of extension officers and to educate rather that prosecute.
RECREATION AND TOURISM
The WNP and surrounding area is a popular tourist destination. It experiences a short summer season of high activity but has the potential for a more extended period of activity. The major forms of recreational activity are water related. In view of the pressure from various interest groups the WNP has been zoned for different activities.
Zoning:
Zoning of the WNP has been planned to accommodate high, medium and low intensities of activity. The high intensity areas are: the Touw River lagoon and most of the estuary as well as most of Eilandvlei. The medium intensity areas are the upper Touw river estuary and the Serpentine. The low intensity areas are the Eilandvlei/Langvlei channel, Langvlei/Rondevlei channel and Rondevlei. (Figure 1)
Boating:
Most forms of boating are permitted on Eilandvlei (high intensity zone), with canoeing allowed on the Serpentine channel (medium intensity zone). Boating is undertaken by both local residents and seasonal visitors, with higher utilization possibly by the latter group. An entrance fee is payable for access to Eilandvlei during peak holiday seasons, and gross income from this source amounted to c. R 24 000 in 1993. Boat numbers on Eilandvlei are not currently limited. Regulations pertaining to the safe handling of boats are enforced.
In the low intensity zone no boating is permitted.
Fishing:
Fishing with hook and line is permitted in Eilandvlei and portions of the Serpentine channel (high intensity zone). Fishing is undertaken primarily by local residents and no charge is levied. The quantity of fish removed is unknown though is unlikely to be substantial. Sea Fisheries regulations with respect to size and bag limits are enforced.
Swimming:
Swimming is permitted in demarcated areas at Eilandvlei (high intensity zone).
Walking/hiking:
Hiking/walking trails have been laid out in the Touw River/Serpentine area on the floodplain, in the forest above Eilandvlei and in the fynbos area north of Rondevlei. A board walk of 1 km has been constructed in the north shore of the Touw River lagoon. There are numerous points on the water Trails and hides are utilised free of charge be both local residents and seasonal visitors.
Birding:
Birders have access to hides at Rondevlei and Langvlei and there are numerous points on the water between the Touw River and Langvlei for birding. The construction of more bird hides for Langvlei and Rondevlei is planned.
Picnicking:
Apart from the camping sites there are several points in the high intensity area where facilities exist for picnicking.
Returns associated with above mentioned activities are included in assessments for boating described above.
Camping and accommodation:
Resorts, NPB and private (high intensity area), providing camping and accommodation facilities are located on Eilandvlei and the Touw River estuary/Serpentine and lagoon. The two resorts operated by National Parks Board are utilised primarily by seasonal visitors, and gross income in 1993 amounted to c. R 1 200 000.
MANAGEMENT AUTHORITY
National Parks Board, PO Box 176, SEDGEFIELD, 6573, RSA
JURISDICTION
National Parks Board
REFERENCES
ALLANSON, B.R. 1981. The coastal lakes of southern Africa. In: Day, J.H. (Ed.) Estuarine Ecology with particular reference to southern Africa. Balkema, Cape Town. pp. 331-344
ALLANSON, B.R. & WHITFIELD A.K. 1983. The limnology of the Touw River Floodplain. South African national Scientific Programmes report no 79, 35 pp.
BIRCH, G.R., DU PLESSIS, A. and WILLIS J.P. 1978. Offshore and inland geological and geophysical investigations in the Wilderness lakes region. Trans. geol. Soc. S. Afr. 81: 339-352
BOSHOFF, A.F. & PALMER, N.G. 1989. Management recommendations for waterbirds in the Wilderness-Sedge- field lakes complex, southern Cape Province. C.P.A. Nature & Environmental Conservation, Int. rep. 1: 28 pp.
BOSHOFF, A.F., PALMER, N.G. & PIPER, S. 1990. Spatial and temporal abundance patterns of waterbirds in the Wilderness-Sedgefield lakes complex, southern Cape Province. Ostrich (in press).
BOSHOFF, A.F. & S.E. PIPER. 1993. An ordination study of the waterbird community of a coastal wetland, southern Cape Province. South African Journal of Wildlife Research 23(1): 17-25.
BREYTENBACH, G.J. 1990. Master plan: Wilderness National Park. Mammals. Unpublished presentation read at workshop on master plan for Wilderness National Park, 6 pp.
COETZEE, D.J. 1983. Zooplankton and environmental conditions in a southern Cape coastal lake system. J. Limnol. Soc. sth. Afr. 9: 1-11.
COETZEE, D.J & PALMER, N.G. 1982. Algemene fisiese en chemiese toestande in Eilandvlei, Langvlei en Rondevlei gedurende 1978. Bontebok 2: 9-12.
CSIR 1981. Wilderness Report no. 1. Evaluation of prototype data and the application of a numerical model to the Wilderness Lakes and Touws River floodplain. CSIR rep. C/SEA 8113. National Research Institute Oceanology, CSIR, Stellenbosch, South Africa.
CSIR 1982. Wilderness Report no. 2. Evaluation of prototype flood conditions and the application of the numerical model to conditions when the estuary mouth was opened. CSIR rep. C/SEA 8255. National Research Institute Oceanology, CSIR, Stellenbosch, South Africa.
DAY, J.H., BLABER, S.J.M. & WALLACE, J.H. 1981. Estuarine fishes. In: Day, J.H. (Ed.) Estuarine Ecology with particular reference to southern Africa. Balkema, Cape Town. pp. 197-221.
DAY, J.H. 1981. Summaries of current knowledge of 43 estuaries in southern Africa. In: Day, J.H. (Ed.) Estuarine Ecology with particular reference to southern Africa. Balkema, Cape Town. pp. 251-329.
DE KOCK, A.C. & BOSHOFF, A.F. 1987. PCBs and chlorinated hydrocarbon insecticide residues in birds and fish from the Wilderness lakes system. Mar. Poll. Bull. 18 413-416.
DE KOCK, A.C. & SIMMONS R. 1988. Chlorinated hydrocarbon residues in African marsh harrier eggs and concurrent reproductive trends. Ostrich 59: 180-181.
DONNELLEY, F.C. 1994. Butterflies of the Wilderness Lakes Area in the southern Cape, South Africa. Metamorphosis 5(4): 155-158.
FAGAN, B.M. 1960. The Glentyre Shelter and Oakhurst re-examined. S. Afr. arch. bull. 15: 80-94.
GELDENHUYS, C.J. 1989. Conservation status of coastal and montane evergreen forest: In: Huntley, B.J. (Ed.). Biotic Diversity in southern Africa: concepts and conservation. Oxford University Press, Cape Town. pp. 224-238.
GOODWING, A.J.H. 1937. Archaeology of the Oakhurst Shelter, George, Trans. Roy. Soc. S. Afr. 25: 229-324
HALL, C.M. 1985. The limnology of the Touw River floodplain. Part II. Aspects of the ecological structure subject to floods, drought and human interference. Rhodes University,Institute Freshwater Studies, investigational rep. no. 85/1: 138 pp.
HALL, C.M., WHITFIELD, A.K. & ALLANSON, B.R. 1987. Recruitment, diversity and the influence of constrictions on the distribution of fishes in the Wilderness lakes system, South Africa. S. Afr. J. Zool. 22: 163-169.
HARRISON, T.D., COOPER, J.A.G., RAMM, A.E.L. & SINGH, R.A. 1995. Application of the estuarine health index to South Africa's estuaries, Palmiet - Sout. Technical Report. Catchment and Coastal Environmental Programme Report. CSIR, Durban.
HARRISON, T.D., COOPER, J.A.G., RAMM, A.E.L. & SINGH, R.A. 1995. Health of South African estuaries, Palmiet - Sout. Executive Report. Catchment and Coastal Environmental Programme Report. CSIR, Durban.
HOWARD-WILLIAMS, C. 1980. Aquatic macrophyte communities of the Wilderness lakes: community structure and associated environmental conditions. J. Limnol. Soc. sth. Afr. 6: 85-92.
HUGHES, D.A. & GORGENS, A.H.M. 1981. Hydrological investigations in the southern Cape coastal lakes region. Rhodes University, Dept Geography, Hydrological Research Unit, rep. no. 1/81.
ILLENBERGER, W.K. In press. The geomorphologic evolution of the Wilderness dune cordons and lakes. Quaternary International.
JACOT GUILLARMOD, A. 1979. Report to the Lakes Area Development Board, George, on invasive weed species in the area of the Wilderness lakes. Rhodes University, Institute Freshwater Studies, special rep. no. 79/3: 18 pp
JACOT GUILLARMOD, A. 1982. Checklist of the aquatic and floodplain vegetation of the Wilderness lakes, southern Cape. Bontebok 2: 41-51
MARTIN, A.R.H. 1962. Evidence relating to the Quaternary history of the Wilderness lakes. Proc. Geol. Soc. S. Afr. 65: 19-42.
McLACHLAN, A., ILLENBERGER, W.K., BURKINGSHAW, J.R. & BURNS, M.E.R. 1994. Management implications of tampering with littoral sand sources. Journal of Coastal Research Special Issue No. 12: Coastal Hazards. 51-59.
ODENDAL, A.W. & KRIGE I.M. 1988. Social science research projects in South African National Parks: introductory notes. Koedoe 31: 105-114.
SCHRIRE, C. 1962. Oakhurst: Re-examination and vindication. S. Afr. Arhaeol. Bull. 17: 181-195.
SIMMONS, R.E. & BARNARD, P.E. 1985. African marsh harriers: requirements for breeding and foraging habitat. Unpubl. rep., Dept. Zool., University Witwatersrand, 4 pp.
REDDERING, J.S.V. 1994. Supply of land-derived sediment and its dispersal in the Knysna estuary: and environmental appraisal. Council for Geoscience Geological Survey Report No. 1994-0024.
RUSSEL, I.A. 1991. Monitoring programme for the Wilderness National Park. Unpublished Internal report, National Parks Board.
RUSSEL, I.A. 1994. Mass mortality of marine and estuarine fish in the Swartvlei and Wilderness lake systems. Southern African Journal of Aquatic Sciences 20(1/2): 93-96.
RUST, I.C. & ILLENBERGER, W.K. In press. Coastal dunes - sensitive or not? Proceedings of Dunes '94 Conference, Port Elizabeth and Stellenbosch.
ROBINSON, G.A. 1985. Management of the Wilderness coastal lakes system. Unpublished paper presented 4 th Symposium Coastal & Ocean Management, Baltimore, Maryland, USA. July/August 1985.
TYSON, P.D. (Ed.) 1971. Outeniqualand: the George-Knysna area. The South African Landscape, monograph no 2. South African Geographical Society, 23 pp.
UNDERHILL, L.G., COOPER, J. & Waltner, M. 1980. The status of waders (Charadrii) and other birds in the coastal region of the southern and eastern Cape, summer 1978/79. Western Cape Wader Study Group, Cape Town, 248 pp.
VLOK, J. 1989. Master plan - Wilderness National Park - the fynbos vegetation. Unpublished presentation read at workshop on master plan for Wilderness National Park, 4 pp.
WEISSER, P.J. & Howard-Williams, C. 1982. The vegetation of the Wilderness lakes system and the macrophyte encroachment problem. Bontebok 2: 19-40.
WEISSER, P.J., WHITFIELD, A.K. and C.M. HALL. 1992. The recover and dynamics of submerged aquatic macrophyte vegetation in the Wilderness lakes, southern Cape. Bothalia 22(2): 283-288.
WHITFIELD, A.K. & H.M. KOK. 1992. Recruitment of juvenile marine fishes into permanently open and seasonally open estuarine systems on the southern coast of South Africa. Ichthyological Bulletin of the J.L.B. Smith Institute of Ichthyology. No. 57. Grahamstown.
REASONS FOR INCLUSION
1. The Wilderness lakes are one of the few coastal lake systems in southern Africa. Geomorphologically their closest counterparts in southern Africa are those on the coast of the Mozambique Plain. Biogeographically three main biotic provinces are generally recognized for southern African estuaries: subtropical, warm-temperate and cold-temperate. The Wilderness lakes belong to the warm-temperate division and together with the nearby Swartvlei system are the only warm-temperate coastal lakes having a marine connection. An indication of the rarity of coastal lakes can be gauged by the fact that in the area there are only 2 coastal lake systems with a marine connection, whereas there are over 20 estuaries. Of the Wilderness Lakes Langvlei and Rondevlei are in the most pristine condition. 2.c The Wilderness Lakes form an important wetland for several species of waterbird during the winter months as conditions deteriorate at the inland wetlands where they breed, usually because these wetlands dry up. These waterbirds are then compelled to move to the coast where wetlands like the Wilderness lakes form a valuable refuge. Three categories of waterbirds that use the wetland in this manner can be recognized: non-breeders, non-breeders with resident breeding populations and moult migrants.The non-breeding category covers those species that visit the area seasonally but do not breed there. Examples are blacknecked grebe Podiceps nigricollis, spoonbill Platalea alba and threebanded plover Charadrius tricollaris.
The second category are those species of waterbirds that enter the Wilderness lakes seasonally, usually winter, where they join the resident population of the same species. It is believed that these migratory individuals breed elsewhere, probably at inland wetlands that dry up seasonally, thus compelling the waterbirds to move to more stable wetlands at the coast. Examples of these species are dabchick Tachybaptus ruficollis, whitebreasted cormorant Phalacrocorax carbo, reed cormorant Rhalacrocorax africanus, darter Anhinga melanogaster, redknobbed coot Fulica cristata, Kittlitz's plover Charadrius pecuaris and blackwinged stilt Himantopus himantopus.
The third category is based on the mounting evidence to indicate that the wetland is an important refuge for several species of Anseriformes during their moult migration. Examples of species that appear to use the wetland as a moult stopover point are spurwinged goose Plectropterus gambensis, Egyptian goose Alopochen aegyptiacus, yellowbilled duck Anas undulata, redbilled teal Anas erythrorhynca, Cape shoveller Anas smithii, southern pochard Netta erythropthalma, maccoa duck Oxyura maccoa and whitebacked duck Thalassornis leuconotus.
Several species of fish use the lakes as a nursery area. Examples are spotted grunter Pomadasys commersonnii, Cape stumpnose Rhabdosargus holubi, white steenbras Lithognathus lithognathus, Cape moony Monodactylus falciformis, leervis or garrick Lichia amia, Knysna halfbeak Hyporhampus capensis and the mullets Mugil cephalus, Myxus capensis, Liza dumerili, Liza tricuspidens and Liza richardsoni. They enter the estuary as juveniles and migrate up interconnecting channels to the lakes where they mature, before migrating back to sea again to spawn. Three of these species (viz. spotted grunter, white steenbras and leervis) are prized angling fish.
3.b The Wilderness lakes regularly support a wide variety of waterbirds (max. = 72 species) or waterfowl (max. = 57 species). Particularly well-represented are the anatidae: 14 of the 17 species resident in southern Africa have been recorded and 10 of these use the area on a permanent or seasonal basis.
3.c Cape shovellers Anas smithii and yellowbilled duck A. undulata occur regularly at the Wilderness lakes in significantly large numbers. The Cape shoveler is a southern African endemic and at times 5 % of their world population occurs at the Wilderness lakes. Yellowbilled duck are more widespread but at times 3 % of their population in southern African occurs at the Wilderness lakes.
30.1 Conservation importance
The Wilderness Lakes form an important wetland for several species of waterbirds during the winter months as conditions deteriorate at the inland wetlands where they breed. The lakes support a wide variety of waterbirds (max. 72 species) or waterfowl (max. 47 species). Three categories of waterbirds can be recognised: non-breeders such as blacknecked grebe Podicpes nigricollis; non-breeders with resident breeding populations for example reed cormorant Phalacrocorax africanus; and moult migrants such as the yellowbilled duck Anas undulata and the Cape shoveller Anas smithii. Large numbers of the yellowbilled duck Anas undulata and the Cape shoveller Anas smithii, which is a Southern African endemic, occur on the lakes. There are two species of waterfowl occurring at the lakes that are classified as rare, namely the little bittern Ixobrychus minutus payesii and the Caspian tern Hydroprogne caspia. Several species of fish use the lakes as a nursery area. Examples are spotted grunter Pomadasys commersonnii, Cape stumpnose Rhabdosargus holubi and Knysna halfbeak Hyporhampus capensis, besides many others. They enter the estuary as juveniles and migrate up inter-connecting channels to the lakes where they mature, before migrating back to sea again to spawn. The surface waters of the lakes have clear open water in the central areas and fringing beds of macrophytes in the littoral zone. Coastal fynbos and evergreen forests border on the lakes.
There are no recognized rare, threatened or endangered plant species in the area but there are some endemics such as Gladiolus vaginatus and Satyrium princeps, among others.
OUTLINE MAP OF SITE
(To be appended)
Degree of Protection
All the area of the lakes, with the exception of Rondevlei form part of the Wilderness National Park. Rondevlei forms part of The Lakes Nature Reserve. Due to the pressure of recreation, the area has been zoned for different activities.
Site Description
The Wilderness Lakes are one of the few coastal lake systems in Southern Africa. The Wilderness Lakes comprise a lagoon and floodplain of the Touws River, linked by a natural channel (the Serpentine) to the tree lakes, Elandsvlei, Langvlei and Rondevlei. The lakes belong to the warm-temperate biotic province and together with the nearby Swartvlei system are the only warm-temperate coastal lakes having a marine connection. Geomorphologically, the lakes are regarded as an example of a barrier lake coast formed by high dunefields because they are coastal lakes connected to an estuary that periodically closes to form a lagoon.
| If you have any comments on this page, or need more information, please contact John Dini at nat_jd@ozone.pwv.gov.za. |
| This page is maintained by the South African Wetlands Conservation Programme and was last updated on 12 January 1999. |