(Population 45000)
As on Upolu Island, much of the south and extreme west coast of Savaii Island, particularly where there are no fringing reefs with inshore moats, is considered too wave-exposed for viable cottonii farming.
On the eastern shore between Salelavalu and Tuasivi there are moat areas inside the reef with sufficient water at low tide for off-bottom farming. Similarly, on the north coast between Saleaula and Sasina (Fig. 5), there are lagoon moat areas with suitable water depth. However, these areas are susceptible to disruptive wave damage and trials are not recommended until commercial production can be established at more favourable wave protected sites. Asau Harbour on the north coast (Fig. 5) is sheltered from the prevailing winds and is a preferred site for initial trials. On the north side of the harbour the reef forms a natural barrier, although the old air strip and road (Fig. 6) were washed away in a cyclone several years ago. At high tide there is now an exchange of ocean water over parts of the Asau reef and into the harbour. Inside the reef on the harbour side there are more than 5 hectares of shallow water reef-flat area suitable for off-bottom farming, and further inside the harbour, the deeper water is suitable for floating raft or long-line farming (Fig. 6). The southern coast of Asau Harbour is considered less suitable because of fresh water inflows around Matavai.
Floating long-line farming may be possible on the south coast, inside the reef at Satupaitea Bay, but trials are not recommended until production can be established at less wave-exposed sites such as Asau harbour.
The first trial established by the author and Fisheries Division at Saluafata was made using the floating raft method (Fig. 7), to minimise the potential loss of the new ‘seed’ stock to fish grazing. It is recommended that this same method be used to establish trial rafts at Mulifanuaa and in Asau Harbour with the remaining ‘seed’ stock from Fiji. Culture lines should be removed after four to five weeks, and the plants divided and replanted on more floating rafts to increase stock volume.
As stock volume increases it is recommended that some cuttings be transferred to the Aleipata area (Fig. 4), and again initial plantings should be made using the raft method to minimise the potential loss of stock to fish grazing. Once the initial stock has been increased, it is recommended that the off-bottom farming method be used for pilot scale farming. The recommended construction method for off-bottom farming is detailed in Figure 8.
The floating raft and floating long-line farming techniques are generally less resilient to wave action damage and storm destruction than the off-bottom method. Consequently, suitable sites for long-line farming in Samoa are located where there is sufficient current and wave exposure to promote viable growth rates but some degree of protection from direct exposure to prevailing south-easterly and easterly trade winds. The long-line method has resulted in production from regions where no suitable shallow water areas exist for off-bottom constant depth farming. There is only one advantage of these floating methods over the off-bottom technique, and that is a decrease in fish grazing damage. The comparative disadvantages are as follows:
The economic viability of long-line and raft farming in Samoa can only be assessed by a pilot scale production units at one of the recommended sites shown in Figures 2 and 6. Mr. Peter Meredith's earlier farming trial suggests that the off-bottom method can be successfully used, at least in the Aleipata region. If commercially viable production can be established using the off-bottom method there would be little need to develop floating methods in Samoa.
The use of cages, which were used in earlier Fisheries Division trials, is not recommended. The impact of herbivorous fish can only really be assessed when commercial farming is attempted. A small number of adult fish can be very destructive to an initial small trial, but may have an insignificant impact on several hectares of commercial farms. It is important to realise that all the major cottonii production areas in Asia and the Pacific have some level of crop loss to fish grazing, and that it is the intensity of the grazing pressure that may determine the viability of any particular site.
Siganid fish (rabbitfish) are know to be very destructive grazers of cottonii. In some cases these fish will completely inhibit the development of commercial off-bottom farms, as was the case in Vava'u, Tonga, during a four-year farming programme in the 1980s. The Vava'u programme provided useful information on the impact of rabbitfish which may be relevant to any development programme in Samoa. In Fiji, where the same species occurs, rabbitfish grazing has never been a significant problem at farming sites.
One shoaling species of rabbitfish is well known and common in Samoan waters, Siaganus spinus (spinefoot), known locally as ‘Lo’. This species is also common in Tonga. There may well be other species of rabbitfish occuring in Samoa. One of the earlier Fisheries Division cottonii trials reported the loss of stock to rabbitfish, although it was not known whether adult or juvenile fish were responsible. Shoals of juvenile and young rabitfish are seen annually in January and February in Vava'u, after spawning in late November and December. These shoals are comprised of small fish only 30 – 80 mm in total length but they can destroy considerably more cottonii than a few adults, which can be up to 200 mm in total length. The juvenile and young fish graze just the surface cells of plants. This causes the outer pigmented (coloured) cells to quickly die, resulting first in a white mottled plant appearance, progressing within days to an overall whitening of dead and decaying plants. The sudden appearance of white branches and decaying white whole plants is often mistakenly identified as a disease. If the numbers of juvenile rabbitfish are high enough, several off-bottom planted hectares of cottonii can be lost in a matter of weeks, and even the protection of ‘seed’ stock with netting is considered impractical and uneconomic for commercial farms.
The appearance of juvenile rabbitfish damage should not be confused with a loss of pigmentation due to ‘ice-ice’, which is incorrectly referred to as a disease. ‘Ice-ice’ is a response to an unfavourable change in environmental conditions, often associated with a lack of water movement and lower than normal salinity. Good farming practices and management can often minimise the overall impact of unfavourable periods when plants are stressed and growth is poor. Many of the most productive farming areas in the world experience some seasonality in growth rates, and periods of unfavourable weather conditions when production is reduced.
The records indicate cyclones have had an impact on all the previous attempts to establish trial cottonii production in Samoa. The loss of small growth trials during cyclones is probably inevitable, but the impact on several hectares of commercial farms is, as yet, unknown in Samoa. In Fiji cyclones have previously hit farming areas in 1984 and in 1990/91, and in both cases farmers collected up sufficient ‘seed’ stock to re-build production after re-constructing farms. The capital required for farm construction is relatively small, and if farmers have experienced a period of cash income from production before the destructive impact of a cyclone, it is likely some producers will be motivated to re-start. Provided some ‘seed’ material can be found, some cash income can be re-generated within two to four months after a cyclone has hit the area.
Developing production at two or more geographically separated sites will also minimize the potential for a complete loss of production over the whole country.
