Towards sustainable utilisation of the fishery resources of the Kowie Estuary, South Africa

Nsubuga, Yvonne Nakalo (2004) Towards sustainable utilisation of the fishery resources of the Kowie Estuary, South Africa. Masters thesis, Rhodes University.

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Abstract

The annual biomass of fish caught from estuaries in South Africa is currently estimated at over 24,800 tons. These estuarine fishes are caught by over 73,000 fishers, most of them recreational. Annual income derived from South Africa’s total estuarine fishery was worth approximately R430,000,000 in 1997. There is increasing concern that unless our estuarine fisheries are effectively managed, we will not be able to sustain these benefits into the future. Two factors that contribute to inadequate management of the estuarine fisheries in South Africa are a lack of data on which to base management decisions, and the lack of indicators by which to assess trends towards sustainability. The main aims of this study were to provide a description of the Kowie estuary fishery, identify suitable indicators of sustainability for this fishery, and assess its sustainability. Boat-based and shore-based roving creel surveys were carried out on the Kowie estuary between July 2000 and June 2001; 1,091 interviews were conducted with linefishers, and 277 interviews with bait collectors. In the boat-based interviews, data were collected on fisher demographics, fishing site, fishing method, choice of bait, fishing duration and catch statistics. In the shore-based surveys, additional data were collected from shore-based linefishers and bait collectors on their perceptions, attitudes, and knowledge of fishery regulations. Total annual fishing effort on the Kowie estuary was estimated at 30,952 angler.hours (SD=154); 84% of it recreational, and the rest subsistence. Most fishing occurred during December and January, and decreased during winter, especially June and July. The annual yield of fish from the estuary was estimated at 16,240 fish (SD=667) or 5.99 tons (SD=0.81). By number, recreational anglers caught 69% of the annual catch. Three species dominated the catch by number: Rhabdosargus holubi (62%), Pomadasys commersonnii (17%) and Argyrosomus japonicus (7%). By mass, the dominant species caught were Argyrosomus japonicus (60%) and Pomadasys commersonnii (19%). Overall catch rate on the estuary was 0.57 fish.ang.-1h-1 (SD=0.24), or 0.298 kg ang.-1h-1 (SD=0.31). Overall catch rate by number was highest in the subsistence sector at 1.13 fish.ang.-1h-1(SD=0.70), while the boat-based recreational sector recorded the highest overall catch rate by mass (0.427 kg.ang.-1h-1, SD=0.625). Argyrosomus japonicus had the highest overall catch rate by mass on the estuary (0.496 kg ang.-1h-1), and Rhabdosargus holubi the highest overall catch rate by number (1.233 fish.ang.-1h-1). Only 19% of the catch of R. holubi was above the minimum legal size, while the estimates for P. commersonnii and A. japonicus were 21% and 25%, respectively. The annual number of bait collecting outings on the estuary was estimated at 2,889, of which 75% were subsistence. The highest numbers of bait collecting outings were recorded in December and April. The Bay of Biscay was the most popular site for bait collecting. A total of five invertebrate species were collected from the estuary to be used as bait, of which the mud prawn Upogebia africana was the dominant species. Total annual number of mud prawns collected from the estuary was estimated at 260,648; of which 41% was collected by subsistence bait collectors. Thirteen indicators were selected to assess sustainability in three fishery sectors on the Kowie estuary: namely, the shore-based recreational linefishery, the subsistence linefishery and the subsistence bait fishery. Social sustainability was evaluated on the basis of the use fishery resources to fulfil Maslow`s basic human needs of food and employment, safety and security, affiliation, self-esteem and selfactualisation. Indicators of ecosystem sustainability assessed the productivity, diversity, disturbance and degree of water quality in the estuary. Institutional sustainability was assessed on the basis that management systems in the fishery should be results-oriented, consent-based, truth-seeking and adaptable. Data on indicator performance was collected during the shore-based roving creel survey, and from published literature. Arbitrarily set reference points were used to assess indicator performance, which was graded on a scale from 1 (indicating minimum probability of sustainability) to 4 (indicating maximum probability of sustainability). Sustainability was illustrated with the aid of amoeba plots. Overall sustainability was low in all three fishery sectors investigated. Nine of the 13 indicators in the shore-based recreational fishery performed poorly, while 11 of 13 in the subsistence line fishery, and 10 of 13 in the subsistence bait fishery, performed poorly. In all three fishery sectors all four selected indicators of institutional sustainability performed poorly. The probability of social sustainability was higher in the shore-based recreational line fishery, where the performance of two of the five selected indicators was very good. The probability of ecological sustainability was lowest in the shore-based recreational linefishery, while in the subsistence linefishery only one selected indicator performed very well. Recommendations made towards assessing sustainability in small-scale estuarine fisheries include the formulation of national policy for assessing sustainability in fisheries, the involvement of fishers in the assessment process, use of fisher perceptions where data gaps exist, and the use of research results to guide future management decisions. Management changes recommended for the Kowie estuary fishery include the formulation of an effective and integrated management plan, identification of the key stakeholders in the fishery, inclusion of fishers in management, the protection of the estuary’s Zostera capensis beds, and the establishment of a programme to increase research and monitoring in the fishery.

Item Type:Thesis (Masters)
Uncontrolled Keywords:Estuaries, Fisheries, Kowie, South Africa, Ecology
Subjects:S Agriculture > SH Aquaculture. Fisheries. Angling
Divisions:Faculty > Faculty of Science > Environmental Science
ID Code:2800
Deposited By: Mrs Carol Perold
Deposited On:09 May 2012 14:09
Last Modified:09 May 2012 14:09
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