THAILAND

The shellfish industry in Thailand is fairly well developed in both the capture and culture sectors. Total annual mollusc production from 1980 to 1986 is shown in Figure 1. Production from 1980 (110,814 MT) to 1985 (199,749 MT) steadily increased with an average annual growth rate of over 14%, however only 139,510 MT was produced in 1986.

The major bivalve species in Thailand along with their annual yields from 1980 to 1986 are shown in Table 1.
Three commercially important species of oyster are captured from natural beds and cultured : Saccostrea commercialis, Crassostrea lugubris and C. belcheri. The first, a small species, is commonly cultured along the east coast of the Siam Gulf. The other two, which are larger species, are produced naturally and cultured mainly on the west coast of the Siam Gulf and on the west coast of Thailand. They command a higher price than S. commercialis mainly because they are consumed fresh.
Although the production for 1985 (8,757 MT) and 1986 (5,500 MT) were lower than in previous years (possibly due to the limited supply of seed) the output from 1980 to 1984 had steadily increased with an annual growth of 20.5%. The present area under oyster cultivation is reported to be just under 1,000 hectares.
The green mussel Perna viridis is one of the most important species in terms of quantity produced in Thailand. Culture of this species has been practised for more than 60 years. Culture areas are distributed from the east coast to the west coast and the major mussel culture provinces are Chonburi, Chachoengsao, Phetchaburi, Prachuab Khirikhan, Chumphon, Phangnga and Pattani. At present over 658 hectares are being employed for this culture system. Mussel landings from 1980 (38,396 MT) to 1986 (60,010 MT) have increased steadily at an average annual growth rate of 13%.
The blood cockle Anadara granosa is a popular species in Thailand and every year the consumption of this bivalve exceeds local production. Therefore Thailand imports yearly several thousand metric tons of marketable-size cockles and seed from Malaysia. In order to reduce the import of cockles, the Department of Fisheries is trying to encourage cockle culture in many provinces. The production of cockles throughout the last decade has been fluctuating around 20–25,000 MT per year. The lowest production was recorded in 1982 (12,356 MT) whereas the highest annual production was recorded in 1985 when 32,302 MT was produced. Production in 1986 dropped to 16,000 MT.
The carpet clam Paphia undulata is an important species in the Thai fishery industry. Thailand has exported canned clams at a rapidly increasing rate in the last five years. All the clams come from capture fishery and, owing to an increase in fishing effort to meet rising demand, stock depletion is becoming a serious problem. The production of this species has increased from 1980, with the highest annual landing recorded in 1985 when 89,726 MT was produced. Production in 1986 dropped to 50,500 MT. Another important species in terms of quantities landed is the horse mussel Arcuatula arcualata. The highest annual production for this species was in 1982 with 32,919 MT. Since then production has been going down and only 7,500 MT was produced in 1986.
Other important species which are collected as food from natural beds include radiated scallop (Amusium pleuronectes), razor clam (Solen abbreviatus), Jackknife clam (Ensis malaccensis), hard clam (Meretrix lusoria), surf clam (Mactra spp.), wedge shell (Donax faba), and top shell (Trochus sp.).

Figure 1. Total annual production of commercially important bivalve species in Thailand from 1980 to 1986.

Figure 2. Total production figures for the periods 1981–1983 and 1984–1986 of the major bivalve species in Thailand.

Table 1: Annual production of commercially important shellfish in Thailand, 1980–1986. (Values: MT).

The green mussel P. viridis along with the carpet clam, P. undulata are the most important shellfish in terms of quantities landed in Thailand. Their combined production output in 1986 was 110,510 MT which accounted for over 79% of the total country shellfish production. The production figures for the species listed in Table 1 for the periods 1981–1983 and 1984–1986 are shown in Figure 2. It can be observed that the cumulative output during the second period increased for the green mussel, carpet clam and cockle but dropped for the horse mussel and oysters. The production percentages of the above species from their total production for the two periods are shown in Figure 3. Among all the species, the carpet clam shows the highest production increase compared to the total, passing from 31.8% in 1981–1983 to 37.7% in 1984–1986. Similarly green mussel landings increased in the latter period, passing from 33.5% to 36.2%. In contrast, all the other species showed a drop in production in the second period.

Table 2 summarises a number of information on the status of bivalve culture in Thailand. The source of seedling for all species is from the wild, however poor recruitment is a major constraint.
For many reasons capture fisheries is becoming less feasible, and as a consequence, coastal aquaculture is receiving a great deal of attention. The development of mollusc culture is one sector which is rapidly growing. Traditional culture methods are being improved and developed through the introduction of techniques initiated in technologically advanced countries. However, one major factor which will influence the expansion of this activity is the ecology of the coastal areas where mollusc culture is mainly practised. More and more areas are becoming dangerously polluted by industrial and domestic wastes and therefore, in addition to farm management, careful monitoring will be required to maintain healthy environmental conditions.
Although at present no depuration of shellfish is practised in Thailand, the DOF is conducting experiments on technical and economically feasible systems for depuration.

Figure 3. Comparative production percentages of major bivalve species in Thailand for the periods 1981–1983 (A) and 1984–1986 (B).

Table 2: Information on status of mollusc culture in Thailand.