Interactions of longtail tuna fisheries in the western South China Sea

T. Yonemori, H. Yanagawa and Lui Yean Pong
Marine Fishery Resources
Southeast Asian Fishery Development Center
Chendering Fisheries Complex
21080 Kuala Ternegganau, Malaysia

ABSTRACT

Longtail tuna (Thunnus tonggol) inhabit the coastal waters from the western Pacific Ocean to the northwestern Indian Ocean. The species mainly occurs in waters of northern Australia, East and South China Sea and North Indian Ocean (including the Red Sea and Gulf of Aden). In the South China Sea area, longtail tuna are found in abundance in the Gulf of Thailand and along the east coast of Peninsula Malaysia. Longtail tuna are caught by Thai purse seine and drift gillnet fisheries and by Malaysian purse seine, drift gillnet and hook-and-line fisheries. The total catch of longtail tuna from this general area has increased rapidly from 14,300 mt landed in 1980 to more than 100,000 mt in recent years; the increase has been the result of a dramatic increase in Thai purse seine landings. Presently about 90% of the longtail tuna catch is from the purse seine fisheries.

Intensive exploitation of longtail tuna by the purse seine fishery in the western part of the South China Sea (especially in the Gulf of Thailand) indicates a possible interaction between the purse seine fishery and other fisheries. This view is suggested by recent decreasing trends in CPUE in all of the other fisheries targeting longtail tuna in the area.

1. DISTRIBUTION AND CATCH OF LONGTAIL TUNA

Longtail tuna (Thunnus tonggol) is one of the typical neritic tuna species which inhabit the coastal waters from the western Pacific Ocean to the northwestern Indian Ocean including the Red Sea and Gulf of Aden (Fischer and Bianchi, 1994). Estimated catches of longtail tuna by FAO statistical areas are shown in Table 1. The annual total catch exceeded 150,000 mt in recent years. The central west Pacific Ocean (Area 71) which includes the South China Sea (Figure 1) recorded the bulk of the longtail tuna catch; the landings from this area exceeded 60% of the total catch.

The catches of longtail tuna in the South China Sea by country are shown in Table 2. The recorded catches include only those for Taiwan, Thailand and Malaysia fisheries. Considering the general continuity of distribution of a migratory species such as longtail tuna, it is suspected that the longtail tuna may not be reported properly in the catch statistics of some countries.

The western part of the South China Sea (Gulf of Thailand and coastal areas off East Peninsular Malaysia) has been known for its abundance of longtail tuna and this species is one of the most important commercial species in this area. Although tagging experiments involving small tunas (kawakawa, Euthynnus affinis, and longtail tuna) have been carried out in waters of the east coast of Peninsular Malaysia since 1990, the recaptures of longtail tuna have not been sufficiently large enough to estimate movements and migration patterns (Raja Bidin, 1990). However, based on the relative differences in catch per unit effort (CPUE) of Thai fisheries and Malaysian fisheries in the area, the main concentration of longtail tuna appears to be in the Gulf of Thailand.

Table 1. Catch of longtail tuna, by FAO Fishery Statistical Area, 1982-91.

Unit: 1,000 M/T

	1982	1983	1984	1985	1986	1987	1988	1989	1990	1991
NW Indian Ocean (FAO 51)* (Iran, Oman, Pakistan)**	13.9	12.6	13.5	36.8	31.3	37.3	40.1	35.6	33	29.4
NE Indian Ocean (FAO 57)* (Thailand, Australia, India)**	7.1	6.7	6	2.5	2	1.5	1.4	1.5	1.1	1.1
CW Pacific Ocean (FAO 71)* (Thailand, Malaysia)**	16.5	50.5	39.2	46.4	47.1	38.2	92.5	82.3	104.9	115.3
NW Pacific Ocean (FAO 61)* (Taiwan)**	6.5	6.1	5.6	5.8	5.5	6.3	6.9	13.2	26.8	17.4
Total	44	75.8	64.4	91.5	85.9	83.2	140.9	132.7	165.8	163.2

*FAO Fishery Statistical Area
**Major Fishing Countries

Figure 1. South China Sea.

2. FISHERIES FOR LONGTAIL TUNA IN THE WESTERN SOUTH CHINA SEA

2.1 Thai Fisheries

The Thai fisheries operating in the Gulf of Thailand and connecting off-shore areas include the purse seine and drift gillnet fisheries. The longtail tuna caught by these fisheries comprise more than 99% of the total longtail tuna caught by Thai fisheries in this area.

Table 2. Catch of longtail tuna, by country, 1976-92.

Unit: Metric tons

		1976	1977	1978	1979	1980	1981	1982	1983	1984
Taiwan		74	420	253	208	179	259	366	323
Philippines
Hong Kong
Kampuchea
Vietnam
Thailand					(12,503)	(8,671)	(11,564)	(23,416)	(53,805)	(44,374)
	Gulf of Thai				10,583	7,962	9,958	16,306	50,449	38,556
	Indian Ocean				1,920	709	1,606	7,110	3,356	5,822
Malaysia			(12,446)	(12,147)	(8,902)	(11,087)	(17,725)	(14,603)	(18,838)	(17,723)
	West Peninsula		2,344	3,191	2,024	4,701	2,632	1,713	2,680	3,075
	East Peninsula		10,102	8,956	6,878	6,386	15,093	12,890	16,158	14,648
	Sabah
	Sarawak
Singapore
Brunei
Indonesia
Total		74	12,866	12,400	21,613	19,937	29,548	38,385	72,966	62,101

		1985	1986	1987	1988	1989	1990	1991	1992
Taiwan					7,290	5,876	5,754	3,624
Philippines
Hong Kong
Kampuchea
Vietnam
Thailand		(48,000)	(48,299)	(65,911)	(92,925)	(82,125)	(102,436)	(84,847)
	Gulf of Thai	45,589	46,404	63,877	91,628	80,596	101,397	79,227
	Indian Ocean	2,411	1,895	2,034	1,297	1,529	1,039	5,620
Malaysia		(19,151)	(16,590)	(25,484)	(26,641)	(17,123)	(17,812)	(28,058)	(35,003)
	West Peninsula	4,551	4,036	6,719	5,035	3,666	4,626	5,051	8,194
	East Peninsula	14,600	12,554	18,765	15,695	9,959	10,014	9,890	8,002
	Sabah				5,101	1,986	721	11,124	16,698
	Sarawak				810	1,512	2,451	1,993	2,109
Singapore
Brunei
Indonesia
Total		67,151	64,889	91,395	126,856	105,124	126,002	116,529	35,003

Fishery Statistical Bulletin for South China Sea Area (Edited by SEAFDEC)

Until 1993, catch statistics of the Government of Thailand sub-categorized the purse seine fisheries into Thai purse seine, anchovy purse seine and luring purse seine fisheries. After 1994 the fisheries were categorized into only two types; the purse-seine and anchovy purse-seine fisheries.

The Thai purse seine operates in the daytime; fish schools are located visually and/or with the aid of sonar before the net is encircled around the school. The luring purse-seine uses electric lamps to attract fish schools at night or use fish shelters (payaos) which do the attracting of the schools (Okawara et al., 1986). The fisheries using these two types of purse seines usually target longtail tuna. The anchovy purse seine is made up of small-mesh netting and operates mostly in nearshore waters (Okawara et al., 1986). The catch of longtail tuna by the anchovy purse-seine is negligible.

Table 3 shows the number of purse seine vessels (Thai purse seine and luring purse seine vessels combined) by size of boat. About 650 purse seine boats are in operation annually; vessels make repeated fishing trips of 3-4 days duration. The most common size vessel is 20-100 tons and the average vessel is generally equipped with modern fishing gear. As shown in Table 4, the purse seine fishery catches a wide range of species. Although sardines, scads and Indo-Pacific mackerel were principal species landed in earlier years, the longtail tuna has become the first or second highest ranking species landed by the purse seine fishery in recent years.

2.1.2 Thai drift gillnet fisheries

The two types of drift gillnets are the Spanish mackerel gillnet (mesh size of 6-10 cm) and the mackerel encircling gillnet (mesh size of 4-4.5 cm). Both types of drift gillnets catch longtail tuna in this area; however, the longtail tuna catch by the mackerel encircling gillnet is a very minor component of the total catch (Okawara et al., 1986).

Table 3 shows the number of Spanish mackerel gillnet vessels by size; the majority of the vessels range in size from 10-50 tons. Approximately 250 of these gillnet vessels operate in the area with vessels making repeated fishing trips of 2-5 days duration. The catch by species of Spanish mackerel gillnet vessels is shown in Table 4; the longtail tuna accounts for about 30% of the catch.

2.2 Malaysian Fisheries

The three types of fishing gears operated by the Malaysian fisheries in waters off the east coast of Peninsular Malaysia include the purse seine, drift gillnet and hook-and-line. The longtail tuna caught by these three types of gear comprise more than 99% of the total longtail tuna catch in this area.

2.2.1 Malaysia purse seine fisheries

The purse seine fisheries of Malaysia can be classified into several groups according to methods of fishing and species targeted (Munprasit et al., 1989). The Statistical Bulletin issued by the Government of Malaysia, however, lists only the purse-seine and anchovy purse-seine fisheries. The catch of longtail tuna by the anchovy purse seine is very small.

Table 3. Number of fishing units targeting longtail tuna, by country, gear type and size of vessel.

Thai Fisheries (Gulf of Thailand)	Gear type	Size	1980	1985	1990
		< 10 (tons)	77	28	47
		10-20	131	69	45
	Purse	20-50	288	348	203
	Seine	50-100	111	206	287
		100 <	2	16	75
		Sub-total	609	667	657
		<10 (tons)	94	29	29
		10-20	107	82	51
	Drift	20-50	66	124	119
	Gillnet	50-100	5	20	34
		100 <			6
		Sub-total	272	256	239
		< 10 (tons)		1	2
		10-20		53	30
	Purse	20-50		72	73
	Seine	50-100		109	140
		100 <		6	3
		Sub-total	320	241	248
Malaysia		<10 (tons)
Fisheries		10-20
(East Coast of Peninsula Malaysia)	Drift	20-50	Majority: 5-10 tons
	Gillnet	50-100
		100 <
		Sub-total	1,487	879	1,053
		< 10 (tons)
		10-20
	Hook &	20-50	Majority: 5-15 tons
	Line	50-100
		100 <
		Sub-total	1,791	877	(1,300;

Fishery Statistical Bulletin for South China Sea Area (Edited by SEAFDEC)

The purse seiners usually operate at night using luring lights to attract fish; the principal species caught include scads, sardines and Indian mackerels. Longtail tuna are caught incidentally; thus, the longtail tuna catch from the Malaysia purse seine fishery makes up a substantially smaller fraction of the catch than the Thai purse seine fishery.

Table 4. Catch of major species by purse seine, drift gillnet and hook and line fisheries in the Western China Sea.

Unit: Metric tons

			1980	1985	1990
Purse Seine	Gulf of Thailand	Total	231,381	418,106	471,298
		Longtall Tuna	3,906	37,973	95,914
			(2%)	(9%)	(20%)
		Scads	53,719	47,202	40,651
		Jack, Trevallies	11,928	41,734	29,319
		Sardines	75,575	64,535	83,555
		Anchovies	1,914	14,827	432
		Eastern Longtall Tuna	2,319	22,785	49,468
		Indian Mackerel	17,104	29,775	15,718
		Indo-Pacific Mackerel	16,925	47,341	42,487
		Others	47,991	111,934	113,754
	East Coast Peninsula Malaysia	Total	50,487	59,381	78,183
		Longtail Tuna	890	2,961	3.671
			(2%)	(5%)	(5%)
		Scads	13,955	28,005	5,046
		Jack, Trevallies	393	131	264
		Sardines	6,572	4,678	8,383
		Anchovies	1,893		3,855
		Eastern Longtail Tuna
		Indian Mackerel	19,331	20,819	8,488
		Indo-Pacific Mackerel
		Others	7,453	2,787	48,476
Drift Gillnet	Gulf of Thailand	Total	11,505	25,172	15,595
		Longtail Tuna	3,108	7,327	4,919
			(27%)	(29%)	(32%)
		Jack, Trevallies	16	1	3
		Scads	245	60	54
		Black Pomfret	95	556	335
		Eastern Longtail Tuna	2,614	11,367	5,356
		Indian Mackerel		25	25
		Indo-Pacific Mackerel		19	17
		N-B King Mackerel	4,486	4,158	3,796
		Others	931	1,650	1,090
	East coast Peninsula Malaysia	Total	14,059	9,905	9,683
		Longtail Tuna	2,465	5,076	1,708
			(18%)	(51%)	(18%)
		Jack, Trevallies	61	45	408
		Scads	1,078	252	904
		Black Pomfret	355	58	69
		Eastern Longtail Tuna
		Indian Mackerel	2,254	497	597
		Indo-Pacific Mackerel
		N-B King Mackerel		1,613
		Others	7,846	2,364	5,997
Hook &Line	East coast * Peninsula Malaysia	Total	14,440	15,616	14,305
		Longtail Tuan	2,833	6,242	4,558
			(20%)	(40%)	(32%)
		Jack, Trevallies	223	425	363
		Scads	2,430	3,594	2,261
		Billfishes	579	146	85
		Indian Mackerel	480	772	138
		N-B King Mackerel	2,633	1,776	1,515
		Sharks	193	291	128
		Rays	173	129	155
		Others	4,896	2,241	5,102

Fishery Statistical Bulletin for South China Sea Area (Edited by SEAFDEC)

While there are several types of drift gillnets used in Malaysia, the Spanish mackerel gillnet (mesh size of 6.5 cm) is the most common gillnet used to catch longtail tuna; this is a similar situation as in Thailand.

Table 3 shows the number of vessels that use the Spanish mackerel gillnets; about 1,000 of these vessels operate in the area annually. The common size of vessel in this fishery is 5 to 10 tons. Fishing is carried out during the day and fishing trips are usually of one day duration. The catch by this fishery is shown in Table 4; longtail tuna make up a substantial part (18-51%) of the total catch.

2.2.3 Malaysia hook-and-line fisheries

The hook-and-line fisheries include handline, bottom longline and trolling. Longtail tuna are caught exclusively by troll lines and surface handlines. Data of the number of vessels fishing for longtail tuna are not available; however, the Malaysian Statistics lists more than 1,000 unclassified hook-and-line vessels. Most of these boats are 5-15 tons in size; fishing trips are from 5-6 days duration. The catch by these boats are shown in Table 4. The catch of longtail tuna comprises a substantial part (20-40%) of the total catch.

3. SIZE SELECTIVITY FOR LONGTAIL TUNA BY FISHERY

The size of longtail tuna caught differs according to the fishing gear used. Figure 2 shows the wide range of longtail tuna taken by the purse-seine fishery; fish range in size from 18 cm to over 50 cm. While the handline fishery also catches longtail tuna ranging in size from 15 cm to 50 cm, the majority of fish is from 25 cm to 40 cm. Since drift gillnets use a restricted net-mesh size, the range in size of longtail tuna caught by the drift-gillnet fishery is narrow; for 1989 the range was from 28 cm to 39 cm.

4. CATCH TRENDS OF LONGTAIL TUNA BY FISHERY

The total catch of longtail tuna from the area increased rapidly from about 10,000 mt in the late 1970s to more than 100,000 mt in recent years; a historical high in catch of 111,000 mt was landed in 1990 (Table 5 and Figure 3). In recent years the purse seine catch has accounted for nearly 90% of the total longtail tuna catch; the drift gillnet catch for 5-8% and the hook-and-line catch for 4-6%.

4.1 Purse Seine Fisheries

The combined catch of longtail tuna by the Thai and Malaysian purse-seine fisheries increased abruptly from several thousand tons landed annually prior to 1983 to 45,496 mt landed in 1983 (Table 5). Since 1983 the longtail tuna catch has shown a remarkable increasing trend, reaching a peak of more than 99,000 mt landed in 1990 (Table 5 and Figure 3). The dramatic increase has been primarily due to the increase in Thai catch; the Malaysian catch has remained at a relatively low level of less than 10,000 tons landed annually.

Figure 2. Length frequency distribution of longtail tuna caught by the Malaysian fishery, by gear type, in 1989 (sampling site: Kuala Terrenganu, Malaysia). (A)

Figure 2. Length frequency distribution of longtail tuna caught by the Malaysian fishery, by gear type, in 1989 (sampling site: Kuala Terrenganu, Malaysia). (B)

Figure 2. Length frequency distribution of longtail tuna caught by the Malaysian fishery, by gear type, in 1989 (sampling site: Kuala Terrenganu, Malaysia). (C)

Figure 3. Catches of longtail tuna in the western part of the South China Sea, by gear type, 1979-91.

Table 5. Catch of longtail tuna in the western South China Sea, by gear type, 1979-92.

		1979	1980	1981	1982	1983	1984	1985
Purse Seine	Gulf of Thailand	5,811	3,906	4,102	4,841	44,017	30,628	38,022
	East P. Malaysia	1,936	890	1,330	490	1,479	2,045	3,275
	Sub-Total	7,747	4,796	5,432	5,331	45,496	32,673	41,297
Drift Gillnet	Gulf of Thailand	4,679	3,734	5,689	11,441	6,372	7,815	7,540
	East P. Malaysia	1,652	2,465	5,413	4,054	5,850	6,130	5,077
	Sub-Total	6,331	6,199	11,102	15,495	12,222	13,945	12,617
Hook & Line	East P. Malaysia	3,098	3,833	8,320	8,346	8,818	6,472	6,242
Other Gears	Gulf of Thailand	93	322	167	24	60	113	27
	East P. Malaysia	162	197	30		11	1	6
	Sub-Total	255	519	197	24	71	114	33
Grand-total		17,431	14,347	25,051	29,196	66,607	53,204	60,189

		1986	1987	1988	1989	1990	1991	1992
Purse Seine	Gulf of Thailand	39,131	57,721	82,929	75,199	95,914	75,802
	East P. Malaysia	1,327	2,721	8,529	2,737	3,670	4,080	3,299
	Sub-Total	40,458	60,442	91,458	77,936	99,584	79,882
Drift Gillnet	Gulf of Thailand	7,232	6,149	8,670	5,372	5,119	3,304
	East P. Malaysia	2,842	4,303	872	1,848	1,708	1,297	1,091
	Sub-Total	10,074	10,452	9,542	7,220	6,827	4,601
Hook & Line	East P. Malaysia	8,348	11,699	6,258	5,351	4,558	4,456	3,574
Other Gears	Gulf of Thailand	41	7	29	25	364	121
	East P. Malaysia	37	42	36	23	78	57	37
	Sub-Total	78	49	65	48	442	178
Grand-total		58,958	82,642	107,323	90,555	111,411	89,117

The marked increase in the Thai purse seine catch has been attributed to increase in catch efficiency; the efficiency gained from the use of fish shelters (payaos), luring light and advanced electronic equipment, e.g., radar, sonar, echo-sounder and satellite navigation (Pramokchutima, 1992). The principal species caught by the Thai purse seiners has shifted gradually from round scads and sardine to Indo-Pacific mackerel, longtail tuna and kawakawa (Yanagawa, 1989; 1992). The shift in target species has been attributed to the increased demand by tuna canneries, especially for white meat tuna such as the longtail tuna. The tuna canneries developed in Thailand in the mid-1980s (Table 6) probably accelerated the targeting of longtail tuna by the Thai purse seiners.

4.2 Drift Gillnet Fisheries

The combined longtail tuna catch by the Thai and Malaysian drift-gillnet fisheries increased to more than 10,000 mt in the early 1980s; the peak catch of 15,500 mt occurred in 1982 (Table 5, Figure 3). Since 1982 the longtail tuna catch by drift gillnets has declined. It was noted that much of the decline in recent years has been due to the general acceptance of the United Nations Resolution of 1992, which called for a ban on large-scale drift gillnet fishing.

Although small-scale drift gillnet fisheries still operate in the western part of the South China Sea, some parts of Malaysia’s EEZ waters in the area have become off-limits for fishing with gillnets; the restrictions were a means to protect marine turtles. The banning regulation went into effect in 1990. While banning of drift gillnets may have contributed to the low catches of longtail tuna by drift gillnets, other factors may be involved. It was noted that the declining trend in longtail tuna catches started earlier than the banning effort; the decline has been noted in the Thai drift gillnet fishery as well as the Malaysian drift gillnet fishery.

4.3 Hook-and-Line Fishery

The longtail tuna catch by the Malaysian hook-and-line fishery increased moderately up to 1987 when a catch of 11,700 mt was reported. However, since 1987 the longtail tuna catch has shown a decreasing trend (Table 5, Figure 3).

5. LONGTAIL TUNA CPUE BY FISHERY

The CPUE of longtail tuna by fishery are shown in Table 7 and Figure 4. The following sections describe the trends in CPUE by fishery.

5.1 Purse Seine Fisheries

The CPUE of longtail tuna by the Thai purse-seine fishery increased sharply in 1983 and continued to show a general increase until 1991 (Figure 4). The increase has been attributed to a shift in target species from scads and anchovy to longtail tuna and to improved fishing technology. The change in target species is shown by the sharp increase in longtail tuna as a percent of the total catch (Figure 5). Evidence that improved fishing technology is responsible for the increase in CPUE of longtail tuna is that the CPUE of other species also increased.

Table 6. Number of canning plants and quantity of tuna products, 1980-90.

Year	1980	1981	1982	1983	1984	1985	1986	1987	1988	1989	1990
No of canning plants	-	14	24	26	38	39	41	41	45	43	42
Quantity (mt) of Little tuna	-	-	-	36,823	60,420	65,577	83,346	92,357	82,176	111,363	114,767
Tuna	-	-	-		85,700	106,325	191,418	195,246	274,911	331,953
Total	-	-	-	36,823	146,120	171,902	274,764	287,603	357,087	443,316

Somsak Pramokchutima (1992): Tuna Fishery Status: Thailand

5.2 Drift Gillnet Fisheries

Similar to the purse seine fisheries, the Thai and Malaysian drift-gillnet fisheries show a marked difference in CPUE (Table 7 and Figure 4). The reason for the difference may be due to differences in operational pattern or to factors such as differences in density of fish in the two fishing areas or differences in mesh-size used by the two fisheries. However, it is notable that a steady decline in the CPUE is observed for both fisheries in the late 1980s.

5.3 Malaysian Hook-and-Line Fishery

The CPUE of the Malaysian hook-and-line fishery increased moderately up to 1987; thereafter, the CPUE showed a steady decline (Table 7 and Figure 4).

6. POSSIBLE INTERACTION BETWEEN FISHERIES

Although some of the differences in CPUE between the Thai and Malaysian fisheries (purse seine and drift gillnet fisheries) may be due to differences in species targeted and in differences in fishing method and pattern, the large differences in CPUE levels cannot be explained very well without referring to other possible factors, e.g., differences in density or being the effects of interaction between the fisheries. If longtail tuna are concentrated in the Gulf of Thailand, an intensive effort by a highly mechanized fishery such as the purse seine fishery may have an effect upon the catch of other fisheries, especially if the resource is being exploited at a level that cannot be sustained. The exploitation rate of longtail tuna in Malaysian waters was estimated at 0.63, whereas the optimum exploitation rate was reported to be 0.49 (Raja Bidin and Rumpet, 1992). Considering the present high catch level of longtail tuna by the Thai purse seine fishery, over-exploitation of longtail tuna may have occurred in Thai waters, as well. The decreasing trends in CPUE of all of the other fisheries in the area in recent years indicate a possible effect of interaction between the purse seine fishery and the other fisheries.

7. DISCUSSION

Changes in the catch of longtail tuna in the western part of the South China Sea suggest that the Thai purse seine fishery may be affecting the other fisheries for longtail tuna in the area. To date, this view is only suggestive based on some catch and CPUE trends. Additional information is needed including evidence of longtail tuna movements in the area and basic population dynamics parameters, e.g., mortality and growth rates.

Presently SEAFDEC plans to aid in the improvement of collection systems for necessary fishery statistics. Plans are also being developed to undertake joint tagging programmes with countries fishing in the area. Finally, a modelling study of interaction among longtail tuna fisheries in the area is being considered for implementation.

Table 7. CPUE of longtail tuna in the western South China Sea, by gear type, 1979-91.

			1979	1980	1981	1982	1983	1984	1985
Purse Seine	Gulf of Thailand	Catch (ton)	5,811	3,906	4,102	4,811	43,916	30,455	37,973
		Fishing day	116,429	117,385	126,567	121,828	118,691	147,566	124,159
		Catch/Day	0.050	0.033	0.032	0.040	0.370	0.206	0.306
	East Coast	Catch (ton)		3,906	1,331	478	1,479	2,045	3,275
	Peninsula	Fishing day		117,385	58,590	47,341	44,318	48,878	47,458
	Malaysia	Catch/Day		0.033	0.023	0.01	0.033	0.042	0.069
Drift Gillnet	Gulf of Thailand	Catch (ton)	2,336	3,108	5,640	10,174	5,711	6.961	7,327
		Fishing day	39,926	35,515	44,478	40,302	47,253	47,457	44,862
		Catch/Day	0.059	0.088	0.127	0.252	0.121	0.147	0.163
	East Coast	Catch (ton)		2,645	5,413	4,054	5,850	6,130	5,077
	Peninsula	Fishing day		269,147	360,476	292,284	216,693	195,392	151,188
	Malaysia	Catch/Day		0.010	0.015	0.014	0.027	0.031	0.034
Hook & Line	East Coast	Catch (ton)		2,833	8,320	8,346	8,818	6,472	6,242
	Peninsula	Fishing day		385,065	412,828	304,560	223,745	193,620	187,897
	Malaysia	Catch/Day		0.007	0.02	0.027	0.039	0.033	0.033

			1986	1987	1988	1989	1990	1991
Purse Seine	Gulf of Thailand	Catch (ton)	39,131	57,721	82,929	75,188	95,914	75,764
		Fishing day	166,639	195,972	189,957	167,285	232,212	152,949
		Catch/Day	0.235	0.295	0.437	0.449	0.413	0.495
	East Coast	Catch (ton)	1,327	2,721	8,529	2,737	3,671	4,021
	Peninsula	Fishing day	37,736	43,245	42,051	45,586	58,034	565,632
	Malaysia	Catch/Day	0.035	0.063	0.203	0.06	0.063	0.007
Drift Gillnet	Gulf of Thailand	Catch (ton)	7,172	6,112	8,426	4,784	4,919	3,304
		Fishing day	56,609	57,485	76,915	46,571	60,377	36,078
		Catch/Day	0.127	0.106	0.11	0.103	0.081	0.092
	East Coast	Catch (ton)	2,842	4,303	872	1,848	1,708	1,297
	Peninsula	Fishing day	180,690	195,972	181,295	199,454	200,968	171,955
	Malaysia	Catch/Day	0.016	0.022	0.005	0.009	0.008	0.008
Hook & Line	East Coast	Catch (ton)	8,348	11,699	6,258	5,351	4,558	4,456
	Peninsula	Fishing day	135,180	169,187	183,160	260,210	308,455	240,622
	Malaysia	Catch/Day	0.062	0.069	0.034	0.021	0.015	0.019

Figure 4. Longtail tuna CPUE trends in the western South China Sea, by gear type, 1979-91.

Figure 5. Change in proportion of longtail tuna in the total Thai purse seine catch, 1979-91.

8. REFERENCES CITED

Fischer, W., and G. Bianchi (eds.). 1984. FAO species identification sheets for fishery purposes, western Indian Ocean, Vol IV (FAO Area 51). FAO Fisheries Department, Rome, Italy.

Munprasit, A., Y. Theparoonrat, Sijin See-Ung, S. Soodhom, Y. Matsunaga, B. Chokesanguan and S. Siriraksophon. 1989. Fishing gear and methods in southeast Asia: II Malaysia. (SEAFDEC, Training Department)

Okawara, M., A. Munprasit, Y. Theparoonrat, P. Masthawee and B. Chokesanguan. 1986. Fishing gear and methods in southeast Asia: I. Thailand. SEAFDEC, Training Department.

Pramokchutima, S. 1992. Tuna fishery status: Thailand. Paper presented at the Fifth Southeast Asia Tuna Conference, General Santos, Philippines, September 1992.

Raja Bidin B. Raja Hassan. 1990. Preliminary results of tuna tagging programme in Malaysia. Paper presented at the Fourth Southeast Asian Tuna Conference, Bangkok, Thailand, November 1990.

Raja Bidin B. Raja Hassan, and R. Rumpet. 1992. Some aspects on longtail and kawakawa in Malaysia. Paper presented at the Fifth Southeast Asian Tuna Conference, General Santos, Philippines, September 1992.

Yanagawa, H. 1989. A preliminary report on the influence of the increase in tuna fisheries upon the other marine fisheries in the Gulf of Thailand. Paper presented at the Third Southeast Asian Tuna Conference, Bali, Indonesia, August 1989.

Yanagawa, H. 1992. The situation of small tuna fishing in the Gulf of Thailand from 1978 to 1988 based on multivariate analysis. SEAFDEC TD/RES/31.