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Commercial seaweeds

Gelidium picker

The south coast is notable for its commercial quantities of the intertidal red seaweed Gelidium pristoides, which has been harvested there since the 1950s for the extraction of agar (Anderson et al. 1989). The agar is of a high quality, and the content varies between 30 and 48% of dry weight (Carter & Anderson 1986). Harvesting is done during Low Water Spring (LWS) tides, by labourers who walk slowly over the rocks and pick the largest tufts by hand. About 100 t dry weight of Gelidium (mainly G. pristoides, but also small amounts of G. pteridifolium and G. abbottiorum) is collected annually between Kei Mouth and Cape St. Francis. The effects of this harvesting on G. pristoides and other intertidal organisms has been investigated and shown to be ecologically minimal (see review by Anderson et al. 1991). The other two species are mainly found in the sublittoral fringe and shallow sublittoral zone, and so the commercial harvesting from the intertidal zone is thought to have little effect on their populations as whole.


Anderson, R.J., Simons, R.H. & Jarman. N.G. (1989). Commercial seaweeds in southern Africa: utilization and research. South African Journal of Marine Science 8: 277-299.

Anderson, R. J., Simons, R. H., Jarman, N. G. & Levitt, G.J. (1991). Gelidium pristoides in South Africa. Hydrobiologia 221: 55‑66.

Carter, A.R. & Anderson, R.J. (1986). Seasonal growth and agar contents in Gelidium pristoides (Gelidiales, Rhodophyta) from Port Alfred, South Africa. Botanica Marina 29: 117-123.

Citing this publication:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town,; Accessed on 19 July 2024