Somsak Chullasorn
Phuket Marine Biological Center, Department of
Fisheries
P.O. Box 60
Phuket 83000 Thailand
ABSTRACT
This report presents an overview of tuna fisheries in the Gulf of Thailand. The data on small tunas, mainly longtail tuna (Thunnus tonggol), kawakawa (Euthynnus affinis) and frigate tuna (Auxis thazard), caught by drift gillnet and purse seine are examined for possible interactions between these two fishing methods. The report also provides information about research on small tunas, fishery development, and prospects for further development. Additionally, problems are identified and recommendations made.
1. INTRODUCTION
Until 1979 tunas were a relatively minor part of the pelagic fisheries of Thailand. The catch statistics of Thailand classified tunas collectively as "bonito" without a breakdown into species. Tunas are caught by purse seines and drift gillnets year-round. The development of a fish canning industry in Thailand during the late 1970s increased the demand for mackerel, scad, sardine, and especially tuna. By 1982 tunas had become the main target species of Thai fishermen (Figure 1) because of the high price offered by the tuna canneries. This demand encouraged Thai fishermen to seek tunas as their target species and to increase the catch through improvement of fishing gears, as well as expanding the fishing grounds farther offshore. The rapid development of tuna fisheries has resulted in a spectacular increase of tuna production, from 3,300 mt in 1971 to 156,208 mt in 1990. Presently, Thailand is the main supplier of canned tuna to foreign markets throughout the world.
2. RESOURCES
2.1 Exploited Species
There are three main species of small tunas caught commercially in Thai waters - longtail tuna (Thunnus tonggol), kawakawa (Euthynnus affinis) and frigate tuna (Auxis thazard). The predominant species, longtail tuna, is preferred by canners and commands the highest price among the three species; the higher price is due to the preferred lighter colour of longtail tuna as a canned product. Besides these three species, skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus), dogtooth tuna (Gymnosarda unicolor) and oriental bonito (Sarda orientalis) are also caught occasionally in small quantities in neritic waters.
2.2 Distribution
Small tunas are migratory and widely distributed along the continental shelf at depths ranging from 20 to 75 m. They occur in large schools in offshore waters and are seasonal visitors to coastal areas. The small tunas concentrate in the inner neritic waters.
Longtail tuna are found farther offshore than kawakawa and frigate tuna. Longtail tuna moves into the Gulf of Thailand and enter the fishery as recruits at a size of 20 cm during October to February; fish larger than 40 cm generally remain in the outer neritic waters. During the northeast monsoon, longtail tuna are abundant in the eastern coast of the Gulf until January. Later they move to the western coast to feed, and by June-July longtail tunas disappear from the west coast, possibly migrating to the South China Sea area to spawn.
Kawakawa are also distributed along the continental shelf throughout the year. Small kawakawa (from 18 cm in length) are captured in the coastal areas in the inner and outer neritic waters and over the continental slope during October-January. Available evidence suggests that this species is not as segregated by size as is the case with longtail tuna.
Frigate tunas are principally distributed in the inner neritic waters. Frigate tuna move to offshore waters during February-May when they reach lengths of about 30 cm.
3. FISHERIES
The purse seine and Spanish mackerel drift gillnet fisheries contribute more than 95% of the total tuna catch (Table 1). The Thai purse seine evolved from the Chinese purse seine and became widely used in Thailand, particularly after 1957. The Thai purse seine has developed as a unique style of seining appropriate to conditions in Thai waters. This gear was developed initially to catch small pelagic fish other than tunas. The targeting of small tunas by the Thai purse seine fishery started in 1982 with the expansion of the tuna canning industry. Thai purse seining is labour-intensive with 30-40 crew members working on vessels ranging in size from 25-30 m. The length of nets range from 800-1,250 m, while net depths range from 70-120 m, and mesh sizes range from 2.5-9.7 cm. Modern purse seiners are equipped with radar, depth sounder, sonar transceiver and satellite navigational instruments. Recently, some purse seiners have been equipped with power blocks to reduce labour and to permit use of longer and deeper nets with large meshes in the wings and bunt.
Spanish mackerel drift gillnets have played an important role in these tuna fisheries, especially in the early period of development. At present, the drift gillnets are less important for capturing tunas when compared to purse seines. The fishing boats used by this type of gear are mostly small to medium-sized vessels ranging from 14-18 m in length. The length of the gillnet varies from 1-12 km, and the depth is usually 7.5 m. The mesh size is rather large, ranging from 9-11 cm stretched. The gillnet are usually operated around islands or near seamounts. The gillnet fishery for small tunas has not changed much; exceptions are an increase in net length resulting from the adoption of mechanised haulers, and a movement farther.
Table 1. Species compositions of tunas caught from the Gulf of Thailand and the South China Sea, 1979-91. LOT=longtail tuna, KAW=Kawakawa, FRI=frigate tuna. Source: Marine fisheries statistics (Department of Fisheries, 1979-91).
Unit: %
|
Year |
Purse Seine |
Drift Gillnet |
||||
|
LOT |
KAW |
FRI |
LOT |
KAW |
FRI |
|
|
1979 |
77.0 |
23.0 |
- |
54.0 |
46.0 |
- |
|
1980 |
62.7 |
37.3 |
- |
54.3 |
45.7 |
- |
|
1981 |
47.8 |
52.2 |
- |
50.3 |
49.7 |
- |
|
1982 |
24.7 |
75.3 |
- |
52.1 |
47.9 |
- |
|
1983 |
64.5 |
25.7 |
9.8 |
43.6 |
56.4 |
- |
|
1984 |
62.6 |
37.4 |
- |
38.1 |
61.9 |
- |
|
1985 |
59.1 |
40.9 |
- |
39.2 |
60.8 |
- |
|
1986 |
54.9 |
45.1 |
- |
42.2 |
57.8 |
- |
|
1987 |
57.1 |
21.4 |
21.5 |
26.9 |
43.1 |
30.0 |
|
1988 |
77.5 |
12.5 |
10.0 |
78.1 |
12.6 |
9.3 |
|
1989 |
68.0 |
18.5 |
13.5 |
50.1 |
39.0 |
10.9 |
|
1990 |
66.0 |
21.7 |
12.3 |
47.9 |
42.0 |
10.1 |
|
1991 |
58.5 |
25.9 |
15.6 |
39.8 |
39.0 |
21.2 |
|
Average |
60.0 |
33.6 |
6.4 |
47.4 |
46.3 |
6.3 |
There are two types of purse seine registered in the Gulf of Thailand - Thai purse seine and luring purse seine. Luring purse seines are modified from Thai purse seines and involve the use of coconut leaves as fish attraction devices. In recent years, the luring purse seines began using modern equipment such as generators, colour echo-sounders, sonar, radar and satellite navigational devices to increase fishing efficiency.
The number of registered Spanish mackerel drift gillnets (Figure 2) showed an increasing trend from 1971 to 1988, with slight declines noted in 1978, 1982 and 1989. The number of Thai purse seines showed a decreasing trend from 1973 to 1983 and, subsequently, they increased dramatically and reached a maximum in 1991. The number of luring purse seines showed a trend that was opposite to the Thai purse seines. However, it is difficult to accurately separate the Thai and luring purse seines because identification of those two types of purse seines is not clear, and the final gear designation is left to the fishermen's discretion during registration. With regard to the number of combined Thai and luring purse seines, the total shows a steady increasing trend from 1971 to 1991 with a marked drop in 1989 (Figure 2).
3.2 Species Composition
The longtail tuna is the dominant tuna species landed by the purse seine and drift gillnet fisheries. During the period 1979 to 1991 longtail tuna made up an average of 60% and 47.4% for the annual catch of the two gears, respectively; the rest of the catch consisted mainly of kawakawa and frigate tunas (Table 1). Skipjack and yellowfin tunas are found farther south in the Gulf of Thailand and in the South China Sea. Presently, fisheries targeting skipjack and yellowfin do not exist.
The percentage of small tunas caught by purse seine and Spanish mackerel drift gillnet are shown in Figure 3. It appears the small tunas were an important part of the Spanish mackerel drift gillnet fishery, even prior to the dramatic increase in demand for tuna in the early 1980s. Small tunas comprised 30-50% from 1972-80, and 60-70% from 1982-91. It may be possible that the increase in the catch of small tunas since 1982 is due to movement offshore by the drift gillnet fishery in response to higher prices offered for tunas. Small tunas caught by purse seines showed a gradual increasing trend throughout the period from 1976-91, and the increase in the tuna portion of the catch has been steady since 1981. In 1981 small tunas comprised only 3% of the total catch, and by 1990 had reached a high of 31%. The non-tuna component of the purse seine catch was comprised mostly of small pelagic fish, i.e., mackerel, sardine, round scad and other carangids.
3.3 Production
The catch of tunas by purse seines showed an increasing trend throughout the period. In 1972, tuna landings by purse seine was only 2,600 mt; annual landings increased gradually to a high of 8,700 mt in 1981. Subsequently, there was a dramatic increase in tuna landings that reached a high of 145,000 mt in 1990. In 1991, the catch declined slightly, accounting for 129,500 mt (Figure 4).
The annual catch of the Spanish mackerel drift gillnet fishery showed an increasing trend from 1971-82. From 1982 to 1988 the catch stabilised at about 11,000-19,000 mt; thereafter, the catch declined and accounted for less than 10,000 mt in 1991 (Figure 4). Since 1982, the catch of small tunas by the Spanish mackerel drift gillnet fishery and the purse seine fishery appear to be headed in opposite directions. The tuna catches of drift gillnets and purse seines were of equal magnitude up to 1982; thereafter, production by purse seines exceeded that of gillnets. The increase was due to improvements in fishing efficiency, expansion of fishing grounds into deeper waters, and an increase in effort by purse seiners. It may be possible that interaction between these two types of fishing gears exists.
Figure 4. Catch of small tunas by species and gear type in the Gulf of Thailand, 1971-91. TUN=total tunas, LOT=longtail tuna, KAW+FRI=kawakawa and frigate tuna.
3.4 Catch and Effort
Catch and effort statistics of Spanish mackerel drift gillnet and purse seine are available from 1972 to 1991. The units of fishing effort used to observe trends in catch are the number of boats and the number of fishing days.
Except for 1991, the number of fishing boats and number of fishing days for the Spanish mackerel drift gillnet fishery showed similar increasing trends throughout the period 1971-91 (Figure 5). Fishing effort reached a maximum of 398 boats, or 76,915 days, in 1988. Catch increased from 2,200 mt in 1972 to a peak of 19,400 mt in 1982, and stabilised until 1988. After 1988 the catch dropped to 10,000 mt, corresponding to the lower level of fishing effort.
The catch of tunas by purse seines showed an increasing trend from 3,200 mt in 1971 to a maximum of 145,000 mt in 1990 (Figure 6). The number of purse seiners showed a gradual increase from 328 boats in 1971 to a maximum of 1,026 boats in 1991. By comparison, the number of fishing days showed wider fluctuations than effort, as measured by the number of boats. It was observed that an increase in purse seine effort occurred during the period from 1975 to 1978, while tuna catches increased remarkably after 1982. The reason for the increase in effort from 1974-78 does not appear to be tuna-related.
3.5 Catch Per Unit of Effort
The catch per unit of effort (CPUE, in kg/day) of combined Thai purse seine and luring purse seine from 1980 to 1991 shows increasing trends for both longtail tuna and small tunas (kawakawa/frigate tuna), especially after 1982 (Figure 7). This increase may be due to increase in fishing efficiency of purse seining due to experience, and also to expansion of the fishery into more productive fishing grounds in offshore waters.
The CPUE (kg/day) of the gillnet fishery shows declining trends for both longtail tuna and small tunas (Figure 8). The declines could be attributed to gear interaction. The trend in the gillnet catch rate contrasts with that of the purse seine fishery. It may be possible that the purse seine is much more efficient, thus making small tunas less available to gillnet that operated in the same area. Another possibility is that the purse seines by fishing further offshore catch the small tunas before they become available to the gillnets which normally operate in more coastal waters.
Figure 6. Catch and fishing effort of purse seine for small tunas in the Gulf of Thailand, 1971-91.
3.6 Change in Size Composition
The data on length frequencies distribution of small tunas had been collected through the sampling surveys at various fish landing sites since 1978. Analyses of size composition for each tuna species have been reported by Klinmuang (1981), Chuenpan (1985), Supongpan and Saikliang (1987), Yesaki (1994) and Pramokchutima (1993). The analyses indicated that the mean size of longtail tuna in the catch from drift gillnet decreased from 40.7 cm in 1979 to 38.5 cm in 1984, 38.7 cm in 1989 and 35.8 cm in 1993. The mean size in the purse seine catch decreased from 41.4 cm in 1983 to 38.8 cm in 1989. It was observed that the mean size and the decrease in size of longtail tuna caught by purse seines and drift gillnet was almost the same. The mean size of kawakawa caught by drift gillnet declined by 4.7 cm from 38.7 cm in 1979 to 34.0 cm in 1993. The mean size of frigate tuna captured by drift gillnet in 1979 was 35.9 cm; the mean size decreased to 32.2 cm in 1993.
The mean length in the catch of small tunas has declined throughout the period for which data are available. Longtail tuna showed the greatest effect from the fisheries. It may be possible that tuna resources have been heavily exploited, suggested by the decline in catch per unit of effort of both purse seine and drift gillnet. Other reasons for the difference in fish size may be the movement of the purse seine fleet to fishing grounds that are farther offshore, or the use of fish aggregating devices.
4. INTERACTION BETWEEN FISHERIES AND RESOURCES
Prior to 1980 the drift gillnet fisheries traditionally focused on Spanish mackerel, especially narrow-barred Spanish mackerel (Scomberomorus commersoni), while the purse seine fishery sought a variety of small pelagic species such as the Indo-Pacific mackerel (Rastrelliger brachysoma), Indian mackerel (Rastrelliger kanagurta), round scad (Decapterus spp.), sardines (Sardinella spp.) and other small pelagic fish. Purse seines and drift gillnet fisheries started to seek small tunas after 1980 to meet the demand of tuna processing plants.
Table 2 shows that the percentage of Spanish mackerel caught by drift gillnet showed a decreasing trend from 53.2% of the total catch in 1972, to a low of 12.7% in 1982 when fishermen began targeting small tunas. From 1983 to 1991, the percentage of Spanish mackerel ranged between 16.5 and 29.3%, while the small tunas showed an increasing trend over the years from 28.5% in 1972 to a high of 79.6% in 1982; thereafter small tunas ranged between 66.0 and 77.3%. The increase in the catch of small tunas in the latter period may be due to the expansion of fishing ground into the deeper waters where small tunas are more abundant than in shallow waters.
Small tunas caught by purse seines from 1972 to 1982 contributed less than 10% of the total catch. After 1982, small tunas became the target species and their percentage in the catch increased, reaching a high of 30.8% in 1990; subsequently, the catch of small tunas dropped slightly to 27.9% in 1991 (Table 3).
It was noted in general that the catch of small tunas by drift gillnets declined after 1982. This decline may be attributed to the low availability of small tunas to this fishing gear due to the increase in exploitation by purse seiners after 1982. The purse seiners gain an advantage over drift gillnetters because they are able to exploit small tunas farther offshore, catching these tunas before they become available to the drift gillnet fishery in coastal waters.
Taking into consideration that the CPUEs of longtail tuna and kawakawa/frigate tunas (Figures 7 and 8) show opposite trends between the drift gillnet and purse seines, it may be possible that interaction between these two fishing gears has occurred as a result of competition for the same resources in the same or adjacent areas.
The data on catch and CPUE between species groups of fish caught by purse seines and drift gillnet have been used to study the dynamics of these fisheries by applying the principal component analysis to assess the impact of the recent expansion of small tuna fisheries (Yanagawa, 1990). The correlation coefficients of catch and CPUE values, factor loading, eigenvalue, and factor score coefficient matrix were calculated.
The results of the analysis of the relationships between tunas and other species caught by purse seines showed that the increase in small tunas catch had a positive impact on anchovy, Indian mackerel, hardtail scad, black pomfret and Indo-Pacific mackerel, and it had negative effects on sardine and round scad. For drift gillnets, the catch of small tunas had a positive impact on Indo-Pacific mackerel and black pomfret, but it had a negative impact on Spanish mackerel and the jack-cavalla-trevally group.
It is presumed that the impact of catches of small tunas on other species can be attributed to difference in fish prices and structure of fisheries. The sardine fishery suffered the greatest negative effect from the increase of tuna fishery because of the change in target species of purse seines. Thai fishing vessels are designed for multi-purpose fisheries, thus it can easily change the target species and fishing gear depending on fishing conditions, fish prices and quantities of catch.
It should be stressed that the interaction between fisheries for small tunas using different fishing gears in the Gulf of Thailand is a growing problem. There seems to be a conflict between purse seiners and gillnetters that fish for small tunas in the same areas. Moreover, analyses of small tunas in Thai waters showed that they are widely distributed and the relative density appears to be greater in oceanic waters. This phenomenon may support the hypothesis that small tunas stocks in Thai waters may be from a common stock, or that they are from an intermingling of fish from waters of neighbouring countries. A careful examination of the catch, effort, CPUE, and species and size composition is planned to address the problem of interaction.
5. RESEARCH
Catch and effort statistics on small tunas have been collected from commercial purse seine and drift gillnet fisheries by the Fishery Statistics Sub-Division of the Department of Fisheries since 1972. The data have been separated into longtail and other small tunas (mainly kawakawa and frigate tuna) since 1979. The available statistics are not reliable enough for the studies on the status of stocks due to the multi-gear nature of the fisheries and the fact that different types of purse seines have been grouped together; these variables make allocation of effort for small tunas difficult. Another problem in gear classification is that the gear, and purse seines in particular, has been modified throughout the period, and this has created confusion for fishermen when registering their fishing gear with the Department of Fisheries. Many of the active purse seiners are not registered, so it may be presumed that fishing effort is underestimated.
Sampling of the commercial small tuna catch was initiated in 1977. Studies on the identification of tuna species found in Thai waters, distribution, species and size composition, mean length in the catch, reproduction, food and feeding, age and growth, and fisheries dynamics, have been made since that time. The results of those studies were compiled by Chullasorn and Martosubroto (1986). At present, attempts are being made to assess the state of tuna stocks based mainly on available catch and effort data.
Another source of information is the tuna sampling programme initiated in May 1987 with assistance from the Indo-Pacific Tuna Development and Management Programme (IPTP). The data collected for 2-1/2 years have been published in "Tuna sampling programme in Thailand" (IPTP, 1990).
Tuna resources have assumed a very important role for the marine capture fisheries of Thailand, especially since the increase in demand for tunas by the canning industry. Previous technical studies on the tuna resources that have been carried out do not seem to be adequate for present management and development purposes. Therefore, particular attention has to be taken on the study on biology and other relevant information upon which to base as assessment on the state of exploitation of tuna stocks in Thai waters and high seas. As a general strategy, the Department of Fisheries continues to focus on research, development, extension, training, statistics, resource management and quality control for export development.
Since tunas are highly migratory and move from waters of one country to another, its stock must be shared by more than one country. Studies on the distribution and migration of tuna resources through tagging programme should be considered necessary. A joint tagging programme between Thailand and Malaysia was discussed at the second meeting of the Tuna Research Groups in 1987 and tagging was implemented in 1990 with the assistance of IPTP. Although the recovery rates of the tagged fish have been very low, the cooperation between countries of this tagging programme should be continued. International organisations in the region, e.g., SEAFDEC, should collaborate to achieve success of the tagging programme.
The study of the effects of environmental factors on the abundance of tunas was also conducted during the survey cruises involving purse seine operations. The results showed that temperature is an important factor in the aggregation of tunas schools. Schools were abundant in the upper boundary of the thermocline layers where temperatures varied from 13-30ºC in depths ranging from 50-220 m. Such environmental studies should be continued and extended to the entire EEZ waters of Thailand to collect the basic information needed for future tuna fisheries development.
6. FISHERIES DEVELOPMENT AND PROSPECTS
The canning industry requires a substantial quantity of raw material (Table 3). With a view to develop the oceanic tuna fisheries by increasing production to meet the canneries' demand, fishing experiments have been conducted using pole-and-line, tuna longline and purse seining methods. During 1978 to 1981 an experimental pole-and-line fishing program was carried out by R/V PRAMONG 10 off Phuket, in collaboration with the FAO/UNDP. The results showed some promise for the development of tuna pole-and-line fishing in Thai waters. Experimental tuna longline surveys were also made off Phuket and Satul provinces, and in the Andaman Sea. The results obtained from these surveys revealed that there are sufficient tuna resources in the oceanic regime to encourage further development of tuna fisheries in the Thai EEZ. To date, Thai fishermen have paid little attention to these other fishing methods; purse seining is still the most popular fishing method.
Table 2. Catch composition by species groups of Spanish mackerel drift gillnet and purse seines in the Gulf of Thailand, 1972-91.
|
Year |
Drift Gillnet |
Purse Seine |
||||||
|
Total Catch (tons) |
Spanish Mackerel |
Small Tunas |
Total Catch (tons) |
Small Tunas |
||||
|
Catch |
% |
Catch |
% |
Catch |
% |
|||
|
1972 |
2,194 |
1,167 |
53.2 |
646 |
28.5 |
24,675 |
2,579 |
10.4 |
|
1973 |
7,633 |
3,496 |
45.8 |
2,880 |
37.7 |
44,286 |
2,190 |
4.9 |
|
1974 |
4,758 |
2,127 |
44.7 |
1,775 |
37.3 |
69,217 |
3,915 |
5.7 |
|
1975 |
6,556 |
3,101 |
47.3 |
2,632 |
40.1 |
74,979 |
4,124 |
5.5 |
|
1976 |
6,393 |
2,596 |
40.6 |
2,385 |
37.3 |
185,432 |
3,321 |
1.8 |
|
1977 |
9,796 |
4,009 |
40.8 |
4,577 |
46.7 |
421,728 |
5,925 |
1.4 |
|
1978 |
6,020 |
2,576 |
42.8 |
2,873 |
47.7 |
347,135 |
3,800 |
1.1 |
|
1979 |
9,432 |
3,914 |
41.5 |
4,328 |
45.9 |
261,457 |
7,547 |
2.9 |
|
1980 |
11,505 |
4,496 |
39.1 |
5,722 |
49.7 |
231,381 |
6,225 |
2.7 |
|
1981 |
18,434 |
5,082 |
27.6 |
11,218 |
60.8 |
312,353 |
8,691 |
2.8 |
|
1982 |
24,348 |
3,086 |
12.7 |
19,376 |
79.6 |
259,713 |
18,123 |
7.0 |
|
1983 |
18,523 |
3,738 |
20.2 |
13,105 |
70.7 |
369,535 |
67,314 |
18.2 |
|
1984 |
24,627 |
4,097 |
16.6 |
18,261 |
74.1 |
345,619 |
48,658 |
14.1 |
|
1985 |
25,172 |
4,158 |
16.5 |
18,694 |
74.3 |
418,106 |
60,758 |
14.5 |
|
1986 |
25,081 |
5,577 |
22.2 |
17,004 |
67.8 |
496,615 |
70,969 |
14.3 |
|
1987 |
23,541 |
5,273 |
22.4 |
15,735 |
66.8 |
493,188 |
80,042 |
16.2 |
|
1988 |
25,924 |
6,307 |
24.3 |
17,114 |
66.0 |
475,203 |
123,670 |
26.0 |
|
1989 |
14,999 |
3,617 |
24.1 |
10,000 |
66.7 |
449,270 |
113,939 |
25.4 |
|
1990 |
15,596 |
3,796 |
25.4 |
10,275 |
65.9 |
471,298 |
145,382 |
30.8 |
|
1991 |
10,740 |
3,150 |
29.3 |
8,304 |
77.3 |
464,083 |
129,461 |
27.9 |
Unit: tons
|
Year |
Total Tuna Used |
Domestic Catches |
Imported Tuna |
|
1982 |
40,320 |
27,722 |
12,598 |
|
1983 |
82,844 |
36,823 |
46,021 |
|
1984 |
146,120 |
60,420 |
85,700 |
|
1985 |
185,577 |
65,577 |
120,000 |
|
1986 |
288,724 |
83,346 |
205,378 |
|
1987 |
287,603 |
92,357 |
195,246 |
|
1988 |
357,087 |
82,176 |
274,910 |
|
1989 |
436,543 |
111,364 |
325,179 |
|
1990 |
474,107 |
114,768 |
359,339 |
|
1991 |
630,627 |
134,369 |
496,258 |
|
1992 |
530,259 |
100,149 |
430,110 |
7. REFERENCES CITED
Cheunpan, A. 1985. Present status of tuna fishery resources in the Gulf of Thailand. Paper presented at the Technical Seminar of the Department of Fisheries, Bangkok, Thailand, 16-18 September 1985: 27 p. [in Thai]
Chullasorn, S., and P. Martosubroto. 1986. Distribution and important biological features of coastal fish resources in Southeast Asia. FAO Fish. Tech. Pap. (278): 84 p.
Department of Fisheries, 1971-1991. Thai marine fisheries statistics based on the sampling survey, 1971-1991. Fisheries Economic and Planning Sub-division, Department of Fisheries, Thailand.
IPTP. 1990. Tuna sampling programme in Thailand. Indo-Pacific Tuna Programme, Columbo, Sri Lanka. IPTP/90/THA/SP. 67 p.
Klinmuang, H. 1981. Studies on the size frequency distribution and length-weight relationship of the tunas in the Gulf of Thailand. Pelagic Fish. Rep. Mar. Fish. Div., Department of Fisheries, Bangkok 24: 39 p. [in Thai]
Pramokchutima, S. 1993. Catch composition of fishes from King mackerel driftnet. Southern Marine Fisheries Development Center, Songkhla, Thailand, Technical Paper No. S/1993: 28 p. [in Thai]
Supongpan, S., and P. Saikliang. 1987. Fisheries status of tuna purse seiners (using sonar) in the Gulf of Thailand. Rep. Mar. Fish. Div., Department of Fisheries, Bangkok 3: 78 p. [in Thai]
Yanagawa, H. 1990. Notes on the situation of the small tuna fishery in the Gulf of Thailand during the decade from 1978 to 1987. Paper presented at the Fourth Southeast Asian Tuna Conference, 27-30 November 1990, Bangkok, Thailand. 19 p.
Yesaki, M. 1994. Interactions between Fisheries for small tunas off the South China Sea coast of Thailand and Malaysia. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 300-319.
