The harvesting of macroalgae in New Zealand

Several species of algae have been commercially harvested in New Zealand, mainly for extraction of agar and alginates. In the past, the harvest was comprised mostly of shore-cast plants. There has been more recent interest, however, in harvesting attached plants of Pterocladia spp., Porphyra spp., Gracilaria sordida, Durvillaea spp., Macrocystis pyrifera, and Ecklonia radiata. The ecological effects of harvesting attached algae depend largely on the sizes of plants, the season of removal, the patch size of clearances, and the proximity and identity of mature plants. These have not been well-studied for seaweeds in New Zealand, but population and life history studies indicate that harvesting methods affect the continuity of algal resources, at least on a local scale, and are crucial factors in their management.