Trends in seaweed resource use and aquaculture in South Africa and Namibia over the last 30 years

Abstract

Abstract The seaweed industry of temperate Southern Africa was last reviewed in 2003. Since then there have been considerable changes. There are three main uses of kelp (mostly Ecklonia maxima, with some Laminaria pallida) in South Africa. The collection of wash-up for drying and exporting for alginate extraction has drastically reduced to very small amounts in recent years. The boat harvest of fresh kelp for abalone feed in land-based farms has reached a plateau of between 4000 and 5000 t fresh per annum. The diver harvest of E. maxima for agricultural liquid plant growth enhancer shows a constant increase over several years, is still growing, and is currently over 3000 t fresh per annum. The small intertidal collection of Gelidium pristoides as export for agar production has maintained a small, sustainable production of around 100 t dry for many years. Former Gracilaria industries in sheltered bays in both South Africa and Namibia have collapsed, and there is currently no commercial collection. There was commercial raft aquaculture production of Gracilaria in Lüderitz Bay, Namibia for a number of years, but this is no longer practised. Currently, the only commercial seaweed use in Namibia is of L. pallida. Annually, ca. 150 t of fresh wash-up is collected, in Lüderitz, to be used as feed in land-based abalone aquaculture. There are a number of small start-up companies experimenting with seaweed products for cosmetics and nutritional products in both countries, some involving species of Ulva and Porphyra. The former species is a major aquaculture product, with around 2000 t fresh yr–1 being produced in integrated land-based systems with abalone.