Field Document No. 4
SURVEY OF LIMU TANGA'U (Cladosiphon sp.) IN TONGATAPU, HA'APAI AND VAVA'U ISLANDS IN TONGA: OBSERVATIONS ON GROWTH IN DECEMBER 1996 | |
by
Ed R. Lovell
Project Consultant
Prepared for the Ministry o Fisheries,
Kingdom of Tonga
The designations employed and the presentations of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organisation of the United Nations concerning the legal or constitutional status of any country, territory, city or area or its authorities, or concerning the delimitation of its frontiers or boundaries.
The Food and Agriculture Organization is greatly indebted to the organizations and individuals who assisted in the implementation of the project by providing information, advice and facilities.
During the period of the first phase project (1986–1992), the FAO South Pacific Aquaculture Development Project (SPADP) defined that seaweed would be one of the most appropriate aquaculture commodities for the Pacific islands for export purpose, that are at present limited in number. The second phase of SPADP starting from 1994 followed the strategy of the first phase and generated awareness in exploration of seaweed farming development in the region.
Although SPADP learned through a scientific reference of the existence of useful seaweed (Cladosiphon) in New Caledonia. SPADP was thoughtlessly not aware of the distribution of a similar seaweed in Tonga until Mr.Kikutani, a JICA aquaculture expert sent SPADP Cladosiphon algae sampled from Tonga in 1995 because of its limited appearance in a certain time. No other countries reported this seaweed in the region other than Tonga and New Caledonia.
A brown algae Cladosiphon is called “Limu Tanga'u” in Tonga and is well known by the people as a seasonally edible seaweed, and it is consumed in the domestic market to a limited extent. Cladosiphon algae is being cultured extensively in Okinawa islands, Japan for domestic food market. Its production was about 10,000 tonnes annually and it was a major aquaculture commodity in volume in Okinawa. It is noted that the seaweed farming in Okinawa is contributing not only in generating income of islanders but also in protecting coastal fisheries resources from over-fishing because of observance of fishing restrictions by fishermen owing to the stabilized and increased income from the seaweed farming.
Fortunately, since the quality of Cladosiphon from Tonga was well accepted in the Japanese market and its market is still growing, two seaweed processing companies agreed to conduct a joint harvest trial with the Fisheries Division in 1996. This survey aimed to grasp the biological and ecological features of this seaweed as well as to assess the viability of its commercial harvest.
Mr.Ed Lovell is an experienced Fiji-based reef biologist. He unveiled extensive areas of natural Cladosiphon habitats in Tonga. These areas would suit its farming production in the future, and SPADP wishes Limu Tanga'u could be one of the largest national export commodities similar to that of squash.
Tanaka Hideyuki
Chief Technical Adviser
1997
SOUTH PACIFIC AQUACULTURE DEVELOPMENT PROJECT (PHASE ii)
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
(GCP/RAS/116/JPN)
Suva, Fiji
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3-1. Field Survey
3-2. Growth Assessment
4-1. Distribution of Cladosiphon sp.
4-2. Sites of General Survey
4.2.1 Tongatapu and adjacent areas
4.2.2 Ha'apai group
4.2.3 Vava'u group
4-3. Aerial Photography of the Sites of Known Cladosiphon Occurrence
4.4 The Aerial Extent of Seagrass Habitats
4.4.1 Thalassia hemprichii and Syringodium isoetifolium as habitats for
Cladosiphon sp.
4.4.2 Comparison of Cladosiphon habitats: Estimate of areas, known
harvest and field sample
4.5 Growth Study
5-1. Life Cycle
5-2. Field Appearance
5-3. Seasonality
5.3.1 Potential effect of temperature on the life cycle of Cladosiphon sp.
5.3.2 El Nino - La Nina cycles and regional water temperature fluctuations
5-4. Potential Consequences of Continuous Harvest
Figure 1: Chart of the Kingdom of Tonga with its South Pacific location (inset)
Figure 2a: The area of initial harvest on Tongatapu off Navutoka (located to the right in the photo). Another site of harvest is to the right of Manima and Oneata ls. See Fig. 2b for the charted area
Figure 2b: Charted area of Fig.2a shown in the bold lined section
Figure 3a: Tonga's most extensive Cladosiphon habitat in the bay south of Atata and Toke l. See Fig. 3b for detail of the chartered area
Figure 3b: Charted area of Fig. 3a shown in the bold lined section
Figure 4a: The seagrass beds adjacent to Uiha l., Ha'apai which potentially host commercial quantities of Cladosiphon The charted area of Uiha and adjacent islands are shown in Fig. 4b
Figure 4b: Charted area of Fig. 4a shown in the bold lined box in the center of the page
Figure 5a: Aerial view of reported Cladosiphon habitats in the seagrass beds west of Koloa l. And north of Oloua l. See Fig. 5b for the charted details of the area
Figure 5b: Charted area of Fig. 5a shown in the bold lined box in the center of the page
Figure 6(a-c): Reported Cladosiphon habitats from off-shore reef areas:
Figure 6d: Areas shown in Fig. 6 a, b on the barrier reef north of Tongatapu l.
Figure 7(a-o): Cladosiphon lifecycle, habitat and experimental design
(a,b) Dispersal of Cladosiphon involves two modes:
The settlements of spores on hard surfaces such as the skeletal material of Halimeda spp.
The Cladosiphon colony is often matted amongst the Syringodium seagrass forming dense layers.
The rope culture design in the field at Navutoka, Tongatapu.
Figure 8b: Seasonal diagram of Cladosiphon okamuranus rectified for Tonga for comparison
Figure 9: Comparative temperature data from Tongatapu and Vava'u l.
Figure 13: Predicted sea surface temperature anomalies at 6, 9 and 12 month lead times
Table 1: Summary of information on the sites surveyed