Gillnetting in nature reserves: a case study from the Kosi Lakes, South Africa

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Abstract

When the Kosi Bay Nature Reserve was proclaimed in 1986 there was a thriving traditional fishery, based on trapping fish, and a growing recreational fishery. In 1992 the Reserve Authorities instituted an experimental gillnet fishery to establish if it were possible to develop and implement a new fishery targeting fish species thought to be able to sustain further fishing pressure. The results and implications of the fishery were analysed both in terms of fish catches and broader conservation goals.The fishery was begun in one area and apparent success there led to its expansion and by the end of 1995 there were four gillnet committees issuing a total of 35 permits to their communities. Various problems arose during the development of the project and these were dealt with through the committees. Of the 88,964 fish caught during the period April 1992 to December 1995, 84.6% were of species designated as “target” as they were perceived to be able to sustain increased fishing pressure. Catch levels appeared to be sustainable and impacts on conservation priority species, such as crocodiles, Crocodilus niloticus, and ecological factors such as annual fish spawning migrations, were assessed and found to be minimal. Communities within and surrounding the Nature Reserve were initially neutral or hostile to the Reserve authorities but by December 1995 relations had imroved considerably and a degree of joint management had been achieved. ©

Introduction

The Kosi Lakes, situated on the east coast of South Africa just south of the Mozambique border, are a series of water bodies about 10 km in length (Fig. 1). The lakes run parallel to the Indian Ocean immediately behind high, vegetated, coastal dunes and the mouth has closed only once in living memory, in 1965 for 106 days. The lakes and much of the surrounding wetland were proclaimed a Nature Reserve in 1987 and listed under the RAMSAR Convention as a wetland of international importance in 1991. Various aspects of the lakes and their fisheries have been described (Tinley, 1964, Begg, 1978, Begg, 1980, Blaber, 1978, Blaber and Cyrus, 1981, Kyle, 1986).

For many generations indigenous people have fished in the lakes (Tinley, 1964, Felgate, 1965) using traps and traditional spears, while in the last 30 years recreational angling has become increasingly popular. Traditional fishing is controlled by the local community, whereas recreational angling is controlled by Provincial regulations (Natal Nature Conservation Ordinance, No 15 of 1974). Other fishing methods, including gillnetting, were termed illegal. Harvested fish species are primarily of estuarine or marine origin (Blaber and Cyrus, 1981, Kyle, 1986).

The Nature Reserve is administered by the KwaZulu Department of Nature Conservation (KDNC) whose policy is to promote the wise use of renewable natural resources. The KDNC saw traditional fishing by indigenous people as an inalienable right of the community while recreational angling, as a tourism attraction, was considered desirable. In the 1980s it was suggested (Kyle, 1986) that extant legal fishing methods did not compete greatly with each other and overall exploitation levels were low.

A tagging study (Kyle, 1986) estimated that traps caught c.5% of the adult fish populations and recreational angling <1%. In 1992, the KDNC proposed an experimental gillnetting project to determine if there was scope for further sustainable utilisation of the fish resources of the lakes. Gillnetting had been carried out illegally in the lakes since the early 1950s (Tinley, 1964) but was suppressed by the authorities as it was believed to interfere with fish migrations, catch too many fish and be difficult to control, being principally a night time activity. Kyle (1992)suggested that if effort and area of operation were controlled, gillnetting could be used to sustainably exploit certain targeted fish species to the benefit of reserve neighbours. Certain fish species, such as spotted grunter Pomadasys commersonni, river snapper Lutjanus argentimaculatus, river bream Acanthopagrus berda, Natal stumpnose Rhabdosargus sarba, sea pike Sphyraena spp. and the kingfishes Carangidae were caught in numbers by both recreational and traditional fishermen but freshwater fish in Lake Nhlange such as the sharptooth barble Clarias gariepinus, and the Mozambique tilapia Oreochromis mossambicus, (Fig. 1) were rarely caught in traps or by rod and line. Largescale pursemouth Gerres rappi, a species abundant in the lakes, was not caught by recreational anglers and only in low numbers in traps. Mullets Mugilidae, were abundant and, although caught in numbers by the traps, were thought to be able to sustain greater fishing pressure. For these reasons freshwater fish, G. rappi and Mugilidae were designated target species for the gillnetting. The ethic behind the project was to sustainably benefit as many local residents as possible and involve them in the management of the fish resource of the lakes. The KDNC decided to implement an experimental gillnet fishery in Lake Nhlange and a phased approach was devised.

It was unlikely that fish migrations would be severely impacted if nets were kept away from channels. Experimental gillnet fishing results indicated that netting in the shallows of Lake Nhlange caught a high proportion of target species (G. rappi and Mugilidae). Netting was considered inappropriate north of Lake Nhlange (Fig. 1) as there were many traps in the lower part of the estuary, which provided a legal, sustainable and controlled way of fishing (Kyle, 1986). Conflict between illegal netters and trap owners had arisen several times in the lower estuary, when the netters were believed to have stolen fish or damaged traps. Netting south of Lake Nhlange was not allowed because of a higher density of crocodiles Crocodylus niloticus and hippo Hippopotamus amphibius. Gillnetting intensity and area of operation were decided upon by the KDNC while implementation was carried out through the local community. This paper describes the evolution of the project and summarises results, progress and problems from inception in 1992 until December 1995.

Section snippets

Methods

Thirty metres of netting were allocated per permit following agreement between the potential netters and the KDNC. No restrictions were imposed on mesh sizes or on the material (monofilament or multifilament) from which the net was made. Mesh size restrictions were considered but a large amount of data from nets confiscated by the KDNC showed that stretched meshes used ranged 60–110 mm, with a mode of about 80 mm, and these were considered appropriate for the fishery.

Kyle (in press)showed that

Effort

There was a progressive increase in the number of permits issued throughout the study (Table 1). Initially the recorded net settings rose in a similar manner and then declined after mid 1994 (Fig. 2). The total monthly catch divided by the number of settings (CPUE) showed no clear overall annual increase or decrease (Fig. 3) suggesting that the “catchability” of fish remained similar throughout the study. On an annual basis there was a tendency for lower CPUE in winter. During the four years of

Discussion

Although traditional fishing has been allowed in marine and other reserves elsewhere (Ramos-Espla and Bayle-Sempere, 1989) gillnetting has not been permitted in such reserves in Africa before 1992. Subsequently it has been tried in the St. Lucia lakes but as yet with inconclusive results (Mann, 1996). Since 1992 the method has been used, on a controlled basis, in the Kosi Bay Nature Reserve to selectively exploit certain fish populations (Kyle, 1994). Gillnetting has been the subject of

Acknowledgements

I thank the KwaZulu Department of Nature Conservation for permission to publish this paper, Diane Kyle, Rudy van der Elst, Bruce Mann and Peter Rutsch for support and assistance with the project and Lynnath Beckley and Pete Fielding for assistance in preparing this paper.

References (42)

  • Anon, 1990. Integrated development of small scale fisheries in West Africa. Model project. Benin. Project findings and...
  • Begg, G., 1978. The estuaries of Natal. Natal Town and Regional Planning Report 41....
  • Begg, G., 1980. The Kosi system: aspects of its biology, management and research. In: Bruton, M.N., Cooper, K.H....
  • Blaber, S.J.M., 1973. Temperature and salinity tolerance of juvenile Rhabdosargus holubi (Teleostei: Sparidae). J. Fish...
  • Blaber, S.J.M., 1978. Fishes of the Kosi system. Lammergeyer 24,...
  • Blaber, S.J.M., Cyrus, D.P., 1981. A revised checklist and further notes on the fishes of the Kosi system. Lammergeyer...
  • Blaber, S.J.M., Whitfield, A.K., 1976. Large scale mortality of fish at St. Lucia. S. Afr. J. Sci. 72,...
  • Bennet, B.A., Hamman, K.C.D., Branch, G.M., Thorne, S.G., 1985. Changes in the fish fauna of the Bot river estuary in...
  • Clover, C., 1992. Plunder of our oceans. Reader's Digest, December,...
  • Compagno, L.J.V., Smale, M.J., Davis, B., Cliff, G., Dudley, S.F.J., 1989. Sharks and the Natal Sharks Board. In:...
  • Cyrus, D.P., 1980. The biology of the Gerreidae, Bleeker 1859 (Teleostei), in Natal Estuaries. MSc. Thesis: University...
  • Cyrus, D.P., Blaber, S.J.M., 1982. Species identification distribution and abundance of Gerreidae (Teleostei) Bleeker,...
  • Felgate, W.S., 1965. An ecological study of the Tembe-Thonga of natal and Mozambique. University of Witwatersrand....
  • Garratt, P.A., 1992. Spawning of riverbream Acanthopagrus berda, in Kosi estuary. S. Afr. J. Zool. 28 (1),...
  • Hardin, G., 1968. The tragedy of the commons. Science 162,...
  • Kothias, J.B.A., Ecoutin, J.M., Gerlotto, F., Hie-Dare, J.P., Lae, R., Durand, J.R., 1981. Fishery statistics in lagoon...
  • Kyle, R., 1986. Aspects of the ecology and exploitation of the fishes of the Kosi bay lakes system, KwaZulu, South...
  • Kyle, R., 1992. Final report and proposal: KwaDapha Gillnetting. KwaZulu Department of Nature Conservation. Unpubl....
  • Kyle, R., 1994. Nhlange gillnetting project. Kosi bay Nature Reserve. Annual report 1993. KwaZulu Department of Nature...
  • Kyle, R., 1996a. A mass incursion and mortality of the Cape cormorant, Phalocrocorax capensis, in the Kosi Bay lakes,...
  • Kyle, R., 1996b. Factsheet on resource utilisation during 1995 in the Kosi Bay Nature Reserve. Internal report. KwaZulu...
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