At present, there are about 48 species of Eucheuma world wide (Dawes, 1974), but only Eucheuma spinosum and E. cottonii (Plate 1) are the main commercially cultivated seaweed in Philippines, Indonesia, and Fiji. Eucheuma culture has been proved technically and commercially feasible, and technology has improved during the last two decades. For instance, in 1978–79, the Philippines had an annual yield (dry weight) of Eucheuma of about 6,272 kg/ha. Ten years later, the production was 3,276 kg/ha/month or approximately 36,036 kg/ha/yr (for a typical 11-month operation). Changes in planting and harvesting methods contributed to this dramatic increase in productivity.
Table 2. Estimated carrageenan production capacities of various countries in 1988.
| COUNTRY | Carrageenan | |
| Quantity (MT) | No. of factories | |
| Argentina | small | 1 |
| Denmark | 3 400 | 2 |
| France | 2 800 | 2 |
| Japan | 400 | 4 |
| Korea (Rep.) | 100 | 1 |
| Portugal | 100 | 1 |
| Spain | 500 | 2 |
| United Kingdom | 100 | 1 |
| United States | 4 500 | 2 |
| TOTAL | 11 900 | 16 |
Source: INFOFISH Fact Sheet, November 15, 1989.
In the early years of seaweed culture, the plant was pruned for harvesting, while the remaining part was allowed to regenerate. Later, the practice was changed to harvesting the entire plant and restocking the farm with vegetative fragments. This selection procedure improved crop quality because mature thalli yield better quality gel and more carrageenan per unit weight of seaweed. Also dry-weight conversion ratio is higher for mature seaweed. With the new method, plants grow faster as indicated by the shorter 40-day culture period in 1988 compared to about 90 days a decade earlier. The shorter culture period enables more frequent harvesting. Other recent practices are rotational stocking and streamlined operations. At any given time, a farm has several “month-classes” of seaweeds; harvested lines are immediately restocked enabling weekly or more frequent harvesting.
