THE LAKES ECO AND GOLF ESTATE HOOGEKRAAL 182 FRESHWATER FISH SURVEY PREPARED FOR STEYN FOURIE: PEBBLE RESORTS JANUARY 2003 CONSERVATION MANAGEMENT SERVICES - KEN COETZEE 4 CHESTNUT STREET, HEATHER PARK GEORGE, 6529 TEL / FAX: 044 - 8708472 FRESHWATER FISH SURVEY LAKES ECO AND GOLF RESERVE DEVELOPMENT PROPERTY: SWARTVLEI ESTUARY, GARDEN ROUTE CONTENTS 1. INTRODUCTION 2. METHOD OF SURVEY 3. RESULTS 4. DISCUSSION 5. FISH SPECIES ACCOUNTS 6. ECOLOGICAL SENSITIVITY 7. CONSERVATION OPPORTUNITIES 8. CONCLUSION 9. MAP 10. LIST OF REFERENCES CONSULTED Swartvlei in the background with the Klein Wolwe entering on the left and the Groot Wolwe River entering on the right. 1. INTRODUCTION The Klein Wolwe River and Groot Wolwe River (also referred to as Diep River on certain maps) are both short coastal acid-water streams, arising on the southern slopes of the Outeniqua Mountains. The natural fish fauna of these rivers are typical of the Cape Fold Mountain Region, being small and naturally restricted in their distribution. Although only 18 species occur naturally in the region, 13 are endemic and until recently not much emphasis was placed on fish conservation or river health. It is therefore not surprising that 9 of these species are threatened with extinction (Skelton 2001). The main threats to the indigenous fish of the region being the introduction of alien fishes and the destruction of river habitats by pollution, over abstraction of water, damming and canalisation and alien plant infestations. Three species of fresh water fishes are found in the coastal streams between Mossel Bay and Knysna namely, Eastern Cape Redfin (Pseudobarbus afer), Cape Galaxias (Galaxias Zebratus), and Cape Kurper (Sandelia capensis). All three being listed in the 2996 IUCN Red Data Book as Near Threatened. Recent genetic studies on the Eastern Cape Redfin and the Cape Galaxias have however indicated that the populations differ significantly throughout their distribution range to the extent that their taxonomical status will have to be re-evaluated. These results unfortunately shift the conservation status of both species to a more vulnerable category than before and thus further emphasises the need to conserve all remaining intact natural fish communities in the region (Pers Comms. E. Swartz). The aim of this study was to survey the Dams and Rivers on the Property of the proposed Lakes Eco and Golf Reserve development, and to determine which freshwater fishes were present as well as to comment on their ecological sensitivity and conservation opportunities. 2. METHOD OF SURVEY 2.1 FISH - Seine net (3x2m, 5 mm mesh size) This method involves a two-man seine net which is pulled through the water three or four times per site. - Hand net (various) This method involves the use of different sized hand nets in the smaller nooks or more vegetated areas, where seine netting is not possible. Hand netting is carried out per site. - Visual observations (Micropterus sp.) This involves looking into the river, usually from an elevated point. Bass and Trout can easily be identified in this manner. The method only works well in clear or shallow water. 2.2 MARCROINVRETEBRATES: MINI SASS (UMGENI WATER 2000) A technique used by the River Health Programme to measure the health of a river and the general quality of the water in that river. It uses the composition of invertebrates living in the rivers based on the sensitivity of the various animals to water quality. Because fish are also dependant on river health and water quality, mini SASS can also be of use when studying fish communities. Two sites in the Groot Wolwe (Sites One and Two) and two sites in the Klein Wolwe (Sites Seven and Eight) Rivers were surveyed. Note: Mini SASS has been tested against the more rigorous SASS method and has been found to be sufficiently close to be of real value (Umgeni Water 2000). Interpretation of the Mini SASS score: 0 - 2 Highly impacted stream 2 - 4 Impacted stream 4 - 6 Slightly impacted stream >6 Good quality stream 3. RESULTS (Refer to attached Map 1 for site references) Site One : Groot Wolwe River, low water bridge 3.1 SITE ONE : GROOT WOLWE RIVER, LOW WATER BRIDGE FISH SPESIES Cape Kurper (Sandelia capensis) Freshwater Mullet (Myxus capensis) Estuarine Round-herring (Gilchristella aestuaria) Mosquitofish (Gambusia affinis) MACROINVERTEBRATES : MINI SASS Total Score : 54 Number of invertebrate groups : 9 Average Score : 6 (Slightly impacted stream) Site two : Groot Wolwe River, below pump house downstream of weir 3.2 SITE TWO : GROOT WOLWE RIVER, BELOW PUMP HOUSE DOWNSTREAM OF WEIR FISH SPECIES Bass (Micropterus sp.) Visual observation Mosquitofish (Gambusia affinis) MACROINVERTEBRATES : MINI SASS Total Score : 53 Number of invertebrate groups : 6 Average Score : 8,8 (Good quality stream) 3.3 SITE THREE : GROOT WOLWE RIVER, UPSTREAM OF WEIR FISH SPECIES Bass (Micropteru sp.) Note : Not confirmed, but a large fish was seen rising in the impoundment above the weir Mosquitofish (Gambusia affinis) MACROINVERTEBRATES : MINI SASS Site Four : Dam (large irrigation dam) No SASS Survey carried out. 3.4 SITE FOUR : DAM ( LARGE IRRIGATION DAM) FISH SPECIES Mosquitofish (Gambusia affinis) MACROINVERTEBRATES : MINI SASS No SASS survey carried out. 3.5 SITE FIVE : DAM (SMALL POND ON PLATEAU) FISH SPECIES No fish were netted although a high density of Ccmmon Platanna (Xenopus laevis) were observed. MACROINVERTEBRATES : MINI SASS No SASS survey carried out Site Six : Klein Wolwe River, tidal influence section downstream of bridge near vlei 3.6 SITE SIX : KLEIN WOLWE RIVER, TIDAL INFLUENCE SECTION DOWNSTREAM OF BRIDGE NEAR VLEI FISH SPECIES Freshwater Mullet (Myxus capensis) Estuarine Round-herring (Gilchristella aestuaria) Mosquitofish (Gambusia affinis) MACROINVERTEBRATES : MINI SASS No SASS survey carried out. 3.7 SITE SEVEN : KLEIN WOLWE RIVER, CONSPIRACY CAVE FISH SPECIES No fish collected or observed MACROINVERTEBRATES : MINI SASS Total Score : 36 Number of invertebrate groups : 8 Average Score : 4,5 (Slightly impacted stream) Site Eight : Klein Wolwe River, uppermost section n property 3.8 SITE EIGHT : KLEIN WOLWE RIVER, UPPERMOST SECTION ON PROPERTY FISH SPECIES No fish collected or observed MACROINVERTEBRATES : MINI SASS Total Score : 25 Number of invertebrate groups : 5 Average Score : 5 (Slightly impacted stream) 4. DISCUSSION Although Eastern Cape Redfin (Pseudobarbus afer) and Cape Galaxias (Galaxias zebratus) were absent from study sites on the Groot Wolwe River and Eastern Cape Redfin (Pseudobarbus afer), Cape Galaxias (Galaxias zebratus) and Cape Kurper (Sandelia capensis) were absent from study sites on the Klein Wolwe River, it cannot be assumed that they are absent from the two river systems altogether. The Eastern Cape Redfin (Pseudobarbus afer) has been recorded from upper reaches of the Karatara River which also feeds into Swartvlei. Easterb\n Cape Redfin (Pseudobarbus afer) are therefore present in the greater system and there is a strong likelihood that they occurred naturally in the Groot Wolwe and Klein Wolwe Rivers. (Pers comms E. Swartz). Cape Kurper (Sandelia capensis) has been recorded from the lower section of the Hoekraal River which also feeds into Swartvlei as well as from Site One in the Groot Wolwe River and hence there is a strong likelihood that it occurred naturally in all the rivers feeding into Swartvlei in the past. (Pers comms E. Swartz). To date, no Cape Galaxias (Galaxias zebratus) have been recorded from the Swartvlei System (Pers comms E Swartz), or the adjacent Wilderness Lakes System (Russell 1999). It is recommended that the upper catchments of both the Groot and Klein Wolwe Rivers be surveyed to confirm the presence or absence of Eastern Cape Redfin (Pseudobarbus afer). These results would contribute towards the future conservation management of the rivers. 5. FISH SPECIES ACCOUNTS (Skelton 2001) 5.1 CAPE KURPER Sandelia capensis (Attains 200mm) Conservation Status (IUCN category: Near Threatened) Occurs in the Eastern and Western Cape Coastal Rivers. This fish is not, as the name suggests, related to the tilapia or kurper family but rather to the Gouramis and Siamese fighters. It favours slow flowing water with plant or root cover, and it preys on insects and other invertebrates or small fish. Many populations have declined and are threatened by habitat destruction and predation from introduced bass. 5.2 CAPE GALAXIAS Galaxias zebratus (Attains 75mm) Conservation Status (IUCN category: Near Threatened) Occurs in the Cape coastal streams and rivers from the Gamtoos to the Clanwilliam Olifants. It favours gentle currents within sheltered banks and feeds on small drifting invertebrates. Threatened by introduced alien predatory fishes and habitat deterioration through water depletion, abstraction and pollution. 5.3 EASTERN CAPE REDFIN Pseudobarbus afer (Attains 110mm) Conservation Status (IUCN category: Near Threatened) Occurs in the coastal rivers from Algoa Bay to Mossel Bay. Prefers clear rocky pools where they tend to shoal in open water feeding mainly from the bottom, on algae and small invertebrates. Many populations of this species have been eliminated by bass. 5.4 LARGEMOUTH BASS Micropterus salmoides (Attains 600mm) •Alien species Introduction to the Cape in 1928. Its natural distribution is North America, but is now widespread in the Western and Eastern Cape Coastal drainages. It favours clear, standing or slow flowing waters with submerged and floating vegetation. Primarily feeds on fish but takes virtually any animal food it can handle including birds, frogs, snakes and small mammals. A major predator of the Western Cape indigenous fishes. 5.5 SMALLMOUTH BASS Micropterus salmoides (Attains 600mm) •Alien species This bass is also native to North America and now occurs in certain rivers in the Western and Eastern Cape as well as KwaZulu-Natal and the highveld region. It favours flowing waters and adults are primarily piscivorus. A major predator of the Western Cape Indigenous fishes. 5.6 MOSQUITOFISH Gambusia affinis (Attains 60mm) • Alien species Introduced into the Cape before 1936 and later bred and distributed by Cape Inland Fisheries Department as a mosquito control agent and forage for bass. This native of North America can tolerate salinities from fresh to higher than seawater. It requires standing water usually with plant cover and feeds on small live organisms, including mosquito and fish larvae. This species proved to ban an aggressive invader species capable of restricting other fish populations by preying on fish larvae. 6. ECOLOGICAL SENSITIVITY The single most important features of Southern African rivers is th degree to which they have suffered anthropogenic disturbances (Davies et. al. 1993). In the case of the Klein and Groot Wolwe Rivers, organic enrichment from agricultural practices in the upper catchment and deliberate introduction of invasive plant and animal species, are the major influencing factors. Bass were introduced widely into streams along the Garden Route. The indigenous fishes lacked natural defences against the large specialised predators and the predators themselves had no natural controls. Consequently the indigenous fishes were quickly eliminated and now survive only in refuge streams beyond the reach of introduced predators. Other introduced species such as the Mosquitofish complete with indigenous fishes for food and space as well as preying on their larvae. Considering the pressure already faced by the indigenous fishes due to the destruction of their habitat, this is often the last shove which is needed to put a population into an extremely vulnerable position. Both Eastern Cape Redfin (Pseudobarbus afer) and Cape Galaxias (Galaxias zebratus) are listed as Near Threatened species and as mentioned have since probably shifted into a more vulnerable category. Cape Kurper (Sandelia capensis) is considered the safest of the three species at this stage. 6.1 GROOT WOLWE RIVER Of the three indigenous freshwater fishes found in the region, only Cape Kurper (Sandelia capensis) - one specimen - was collected at one locality (Site One). The introduced Mosquitofish (Gambusia affinis) was by far the most abundant fish at this site. The presence of Bass (Micropterus sp.) And Mosquitofish (Gambusia affinis) at Sites Two and Three explains the lack of any indigenous fish species as the SASS Results indicated good water quality and the river was ideal fish habitat with continuous flow and large clear pools. 6.2 KLEIN WOLWE RIVER Although a large portion of the river on the property has a very steep gradient and is not ideal fish habitat (no fish located at Sites Seven and Eight), the lower freshwater section just before entering the vlei and the upper catchment are more suitable. Neither were surveyed as the lower freshwater section is inaccessible due to dense alien plants and the upper catchment is not within the study area. The presence of Mosquitofish (Gambusia affinis) in the lower estuarine section (Site Six) is a matter of concern. The SASS results also indicate that the Klein Wolwe is more susceptible to nutrient enrichment as the average scores were lower (4,5 and 5 : slightly impacted stream) and, as well as having a foul smell, the water colour was not natural. The main reason for this is probably due to it having a smaller largely transformed catchment, and therefore a much lower base-flow compared with the Groot Wolwe River. It is of utmost importance that thee freshwater fishes are placed under no additional threat by the further introduction of alien fishes or plants into the dams, rivers, or ponds on the property, be it for recreational or aesthetic purposes. 6.3 GENERAL FACTORS CONSIDERING ECOLOGICAL SENSITIVITY The Freshwater Mullet (Myxus capensis) is a marine species but in the course of its life cycle it enters freshwater rivers. Dams and weirs, obstructing the passage into rivers have caused a decline in populations (Skelton 2001). Similarly due to over abstraction of fresh water, many rivers are no longer suitable corridors for fish migration which also has a detrimental effect on this species. The Swartvlei estuary, which is dependant on an inflow of fresh water from its rivers for normal functioning, is an important habitat and nursery area for estuarine and juvenile marine fish as well as roost and breeding places for a diversity of bird species. The quiet backwaters such as the Klein and Groot Wolwe River deltas, where abundant cover and food in the form of aquatic plants are available, are exceptionally important in this case. Swartvlei is a wetland of international importance and is a designated Ramsar Site (Barnes 1988). Dams, and waterways associated with marinas (part of the planned development), alter the natural flow of estuaries with either favourable or unfavourable consequences. Increased human activities associated with such developments however lead to a deterioration of water quality due to seepage of fertilisers, septic tank effluent, waste discharge and oil spills (Breen and McKenzie 2001). 7. CONSERVATION OPPORTUNITIES 7.1 REMOVAL OF INTRODUCED FISHES FROM DAMS, PONDS AND RIVERS Introduced fish species in ponds or dams are always a threat to the adjacent streams and rivers as there is the likelihood that these impoundments can overflow during floods and the fish may escape. The removal of introduced fishes from the rivers will allow for natural recovery of the indigenous species as both rivers possibly have natural populations in their upper reaches. The introduction of suitable species into dams should be considered. Suggested species in this case would be: Freshwater Mullet (Myxus capensis) and the introduced sterile triploid Grass Carp (Ctenopharyngodon idella), which can be used for weed control in dams. The indigenous species from the Wolwe rivers are a further option. By legislation, any of the above recommendations may only be carried out once consultation with the Western Cape Nature Conservation Board and an aquatic ecologist has taken place and approval has been obtained. The weir in the Groot Wolwe River 7.2 THE WEIR AS A CONSERVATION TOOL The weir could in fact be a valuable conservation tool, as it could act as a barrier to prevent alien fish downstream from moving upstream. Alien fish could be eradicated from the upstream section of the river, which would allow indigenous species to re-colonise from populations in the upper catchment (to be confirmed). In this case it would not be feasible to attempt to rid the downstream section of alien fish species as it would require the entire Swartvlei System to be cleared. Both Bass [personal observation of Bass (Micropterus sp.) in Island Lake] and Mosquitofish (Gambusa affinis) tolerate saline water and could therefore be widespread throughout Swartvlei. A fishway would thus not be recommended to be built into the weir, as it would allow alien fish from downstream to access the upstream section. The Bass (Micropterus sp.) in the lower section of the river could be targeted by sport anglers as a means of keeping the numbers down. 7.3 REMOVAL OF ALIEN VEGETATION IN THE CATCHMENTS OF THE RIVERS It is a well known fact that indigenous vegetation is more water efficient than alien plant infestations such as Hakea, Wattle and Pine. Removal of the thirsty aliens results in a greater water yield which leads to an increase in the base flow of the rivers (Davies et. al. 1993), thereby allowing for their natural functioning to resume. The systematic clearing of alien plant infestation on the property is a priority. 7.4 ALLOW FOR RESERVE LEVEL OF FLOW IN THE RIVERS According to the White Paper published on Water Policy, April 1997; the amount of water abstracted from a river should not exceed the Reserve Level which has the purpose of providing for basic human needs and the environment. (Breen and McKenzie 2001). In the case of the Lakes Eco and Golf Reserve Development, it is essential that the Reserve Level of both the Klein Wolwe and Groot Wolwe Rivers are determined by means of a detailed study in order to ensure that the development needs do not exceed the ecological requirements for the rivers and estuary to perform their natural functions. 8. CONCLUSION There is no doubt that the area earmarked for development is highly sensitive. The purpose of this study was to determine which freshwater fishes are present on the Lakes Eco and Golf Reserve Development property. It would however have been inappropriate to comment on the freshwater fish in isolation as the Swartvlei Estuary and the rivers which feed into it function as an ecological unit and therefore need to be managed as such. Finally, although the property was severely mismanaged in the past due to the extent of the alien fauna and flora infestation, it should be recognised, and absolute care should be taken not to impact on the environment any further but rather to restore it to its former natural state. 10. LIST OF REFERENCES CONSULTED 1. Barnes KN. 1988. The Important Bird Areas of Southern Africa. Birdlife South Africa. Johannesburg. 2. Breen CM and McKenzie M (eds). 2001. Managing Estuaries in South Africa : An Introduction. Institute of Natural Resources, Pietermaritzburg. 3. Davies BR and Day K. 1998. Vanishing Waters. UCT Press. 4. Davies BR, O’Keeffe JH and Snaddon CD. 1993. A Synthesis of the Ecological Functioning, Conservation and Management of South African River Ecosystems. Water Research Commission Report no. TT62/93. 5. Impson ND. 1998. Distribution, Conservation Status and Monitoring Requirements of Southern Cape Freshwater Fishes. Western Cape Nature Conservation Board. Unpublished report. 6. Lubke R and de Moor I. 1988. Field Guide to the Eastern and Southern Cape Coasts. UCT Press. 7. Mini SASS. The South African Scoring System for Monitoring River Health. Umgeni Water. P.O. Box 9, Pietermaritzburg, 3200. 8. Roets W. 2002. Guidelines for Monitoring and Management of Aquatic Ecosystems (Rivers, Estuaries and River Mouths) in the Gouritz Region. Western Cape Nature Conservation Board. Unpublished report. 9. Russel IA. 1999. Freshwater Fish of the Wilderness National Park. Koedoe 42 (1): 73 - 78. 10. Skelton PH. 2001. A Complete Guide th the Freshwater Fishes of Southern Africa. Struik Publishers. 11. Skelton PH. Undated On Bass in Blindekloof - The Impact of an Alien Predator on a Wilderness Stream. J.L.B. Smith Institute of Ichthyology. Unpublished report. 12. Swartz E. 2003. Personal communications. Molecular Ecology and Evolution Program. Department of Genetics. University of Pretoria. 13. Treasure A. Undated. Land Use Impacts on the Aquatic Fauna of the Olifants River, with Particular Attention to the Endangered Endemic Fish Species and Invertebrates. A study submitted to Pretoria Software Solution (Pty) Ltd. Unpublished report.
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