This manual has been prepared for the training course on Gracilaria culture under the Regional Seafarming Development and Demonstration Project (RAS/90/002) to be held at Zhanjiang Fisheries College, Zhanjiang, China in August, 1990. The training course includes processing of seaweeds, thus the manual devotes a chapter on the properties, manufacture and application of agar, algin and carragenan. This valuable resource is available for online viewing at fao.org.
Gracilaria is a group of warm water seaweeds. There are more than one hundred species in the world, some of which have very important economic value. Gracilaria is used as food and in the preparation of food products. It is also an important raw material in agar-agar production. At present, the world’s annual output of Gracilaria is about 30,000 tons, dry weight, most of which comes from natural production. For example, the natural production in Chile, Argentina, and Brazil accounts for one third of this total output. With the increasing demand for Gracilaria, greater attention has been focused on the development of its artificial culture by many countries, especially those in Southeast Asia. China is the earliest country that artificially cultured Gracilaria. Today, the culture area in South China is about 2,000 ha producing 3,000 tons dried material annually. Taiwan produces 1,000 tons dried Gracilaria yearly from 400 hectares under cultivation.
Nowadays, Gracilaria is cultured mainly using the following methods: bottom culture, raft culture, stake-rope culture and pond culture. Pond culture can be divided into two systems, monoculture and polyculture with shrimp and other species. The varieties of culture methods can be adapted for different areas.