By:
P R A U L A I C H A N T A W O N G
Andaman Sea Fisheries Development Center,
77, Tumbon Vichit, Amphoe Maung, Phuket 8300, Thailand e-mail afdec@phuket.ksc.co.th
Status of Small Pelagic Fish Resources and Fisheries in Thai Waters Praulai Chantawong2
A ndam an Sea Fisheries D evelo p m ent C enter,
77 T um bon V ichit, A m phoe M au ng , P h u k et 8300, Thailand e-m ail afdec@ p h u k et.k sc.co .th
Abstract
The status of the pelagic fisheries and resources in Thai Waters are provided basing on the Fisheries Statistic of Thailand for 1980 - 1995 period. An attempt is also made to assess the current status found among major small pelagic stocks, namely Indo-Pacific mackerel, Indian mackerel, round scad, small tunas, anchovies and sardines. Other technical reports pertaining to pelagic fisheries and resources are also reviewed. In the Gulf of Thailand, most of small pelagic fish have been over-fished, except hardtail scad and king mackerel. In the Andaman Sea, the stock of Indo-Pacific mackerel, which located in the lower part of the coast, and banded trevally show indication of overfishing. To date the recovery of these stocks seems to have improved. For Indian mackerel, round scad, sardines, small tunas, hardtail scad, and bigeye scad, no drastic changes in their catches imply sustenance these resources.
1. In tro d u ctio n
R apid d evelopm ent o f Thailand's fisheries in th e past tw o decades has p ro m o ted the cou n try into th e w orld's fron tru n n er in fishery industry. In 1996, m arine fishery acco un ted fo r 78% o f th e to ta l fishery p ro d uctio n, o f w hich 70% w a s th e con trib ution from th e G u lf o f T hailand and th e A ndam an Sea shared the rest. N evertheless, th e leap and b o u n d o f fishery develo pm en t has led to ov er exploitation o f fishery reso u rces, particularly dem ersal fishes and invertebrates. A t th e sam e tim e, th e catch o f pelagic po p ulatio ns has increased significantly as well. T he share o f pelagic catch acco un ted fo r 33 % -3 8 % o f th e to tal m arine fishery yield during 1991-1996, w h ereas this po rtio n w a s only 2 4 % -2 8 % from 1979-1982. D urin g th e period o f 1972-1982, th e pelagic catch from th e G u lf o f Thailand and A ndam an Sea w ere 3 1 3 ,0 0 0 -3 7 9 ,0 0 0 m etric to n nes (m t) and 30 ,0 0 0 -4 4 ,0 0 0 m t, respectively. T hese catches had m arked increased from b o th regions in recen t years as show n by th e catch d a ta during 1989- 1996: 5 5 9 ,0 0 0 -7 0 7 ,0 0 0 m t and 100,000-288,195 m t from th e G u lf and th e A ndam an Sea, respectively.
Small pelagic fishes such as Indo-Pacific m ackerel, small tunas, scads, king m ackerel, etc, are gaining m o re im p ortan t econom ically. They had becom e th e m ain ta rg e t species for T hai fisherm en since 1975 because o f attractive prices offered by dom estic consu m er and fish canneries. A cco rding to th e Fisheries Statistics, th e to ta l catches o f small pelagic fish in T hailand w as 9 17,55 0 m t in 1996 and increasing up to th ree tim es com pared w ith 3 9 5 ,54 0 mt in 1982 (D ep artm en t o f Fisheries (D O F), 1984b and 1999). A t present, Thailand is th e main supplier o f canned fish and o th er fish p ro d u cts to foreign m arkets th ro u g h o u t th e w orld.
A nyhow , th e rapid fisheries developm ent m ay lead to th e d eterio ratio n o f small pelagic stock s
2 Andaman Sea Fisheries Development Center, 77 Tumbon Vichit, Amphoe Maung, Phuket 8300, Thailand e-mail afdec@phuket.ksc.co.th
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in Thailand. Thus, studies on small pelagic sto cks are u rg e n t in finding o u t th e cu rren t problem s, situatio n and status.
2. D evelo p m en t o f Sm all P elagic Fisheries
D ev elo p m en t o f pelagic fisheries in Thailand w as resulted from ad o p tio n o f high efficiency p u rse seines (84 % o f to ta l pelagic catch in 1995 (D O F, 1995b)), ex pansion o f n ew fishing g ro u n d b o th inshore and offshore, and also th e developm ent o f n ew fish-luring techniques. F o r exam ple, Payao o r fish aggregatin g device (FA D ) are applied fo r day-tim e catching w hile lighting tech niq u es especially fo r light luring p urse seine (L P S ) w e re d eveloped in 1973 by installing a p o w e r g e n erato r on board. T he techn iqu e has beco m e a p red om in an t fishing g e a r fo r m ixed ta rg e t pelagic species since 1982. A nchovies p u rse seine (A P S ) w hich com m only u sed to catch anchovies in coastal areas have also b een developed to o p e ra te w ith light luring fo r a ttractin g th e fish school at night tim e as w ell as extending o p e ra tio n ran g e offshore. B esides fro m catching th e ta rg e t species, th e technique is applicable to c atch m ixed small p elagic fish a t night. Subsequently, larg er p u rse seine b o ats (T u n a p u rse seine, T U N ) w ere dev elo p ed as to increase th eir fishing capacity fo r catching coastal tu n a s in d e ep e r w ater.
Since 1985, th e vessels h av e b e en fitted w ith electronic equipm ent such as d e p th reco rd er, sonar, and o th e r equipm ent. In 1990, an installation o f lab or saving devices o n b o a rd has b een very p o p u la r am ong fishing vessels. T he developm ent resulted in a sp ectacu lar in crease in sm all pelagic c ap tu res m o re th re e tim es in 1996 th a n in 1982.
3. F ish in g gears
P u rse seines are basically classified into reg u lar p u rse seines (R PS ), anchovy p u rse seine (A PS ) and C hinese p u rse seine (C PS). R P S consist o f T hai p u rse seine (T P S ), g re e n p u rse seine (G P S ), fish ag greg atin g device (F A D ), light luring p u rse seine (L P S ) and tu n a p u rse seine (T U N ). A pp endix 1 show s th e fishing o p e ratio n m etho ds o f p u rse seines (M u n p rasit and M u ttav ee, 1986).
In general, th e com m on m esh size u sed in T P S , L P S , F A D are approxim ately 2.5 cm;
th e len g th and d e p th o f th e n e t ran g e in b e tw ee n 3 0 0 -1 ,2 0 0 m and 4 0 -1 5 0 m, respectively, and n um ber o f crew is in th e ra n g e o f 2 5 -4 0 persons. F o r C PS, th e m esh size is ab o u t 2.5 cm, 30 0 - 500 m in len gth and 50-70 m in d e p th and n um ber o f crew is ab o u t 2 0 -3 0 persons. T h e length, d ep th and m esh size o f G PS n e t are 5 00 -1 ,3 0 0 m, 60-14 0 m and 3.8-4.3 cm respectively, and n um ber o f crew ran g es b e tw ee n 2 5 -4 0 persons. F o r A PS, th e m esh size is ab o u t 1 cm , 2 0 0 -5 0 0 m in len g th and 15-80 m in depth, and num ber o f crew is a b o u t 5-30 persons. F o r th e T U N , th e b o a t len g th is lo n ger th a n 24 m; th e len g th o f th e n e t is b etw een 1,200-1,600 m w ith th e d e p th o f 120-150 m and th e m esh size is 9.4 cm. T he nu m b er o f crew is b e tw een 35-45 person s. T he g e ar is su b stitutab le to b o th L P S and T P S fo r catching o th e r pelagic species in eith er coastal o r offshore areas by using th e n et w ith m esh size o f 2.5 cm.
R P S , C PS and A PS are largely reg istered g ears along th e G u lf o f T hailand and th e A ndam an Sea. T he re g istered R P S show ed a steady increase from 361 and 63, G u lf o f T hailand and A n d am an Sea, respectively in 1971 and reach ed th e p e ak o f 1,026 in 1991 (G u lf o f Thailand) and 273 in 1994 ( A ndam an Sea). T here w a s a slight d ecrease b e tw ee n 1992 to 1996 (909 to 7 0 7 ) in th e G u lf and 1994 to 1996 (237 to 198) in th e A ndam an Sea. T h e num b er o f reg istered C PS w as b e tw ee n 1- 3 4 units from 1971-1976 in th e G u lf and 12-50 units fro m 1971-1992 in th e A ndam an Sea. T he num ber o f th e gear show ed a steep decline and th e re w as no re c o rd in C PS registered num ber since 1977 in th e G u lf and 1993 in th e A ndam an Sea. T h e reg istered A PS indicated a continuously increase from 42 in 1971 and reached 370 in 1996 in th e G u lf and show n flu ctu ated in th e range o f 2-272 units from 1971-1996 in th e A ndam an
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Sea. T ren d o f registered sh o w ed abruptly decreased from 272 units in 1989 to 30 un its in 1996 (Fig. 1).
F ig . 1 N u m b er o f registered o f purse sein ers (R P S , C P S and A P S ) in th e A n d a m a n Sea (d ash lin e , 1) and th e G u lf o f T h ailan d (th ick lin e, 2) d u rin g 19 7 1-1996.
Source: Thai Fishing V essels Statistics, D O F 1972a-1998a.
4. S p ecies C o m p o sitio n
T he m ain pelagic fishes cau g h t by com m ercial fishing g e a r during 1980-1995 consists o f Indo-P acific m ackerel (R a stre llig e r brachysom a) , Indian m ackerel (R. ka n a g u rta ), ro u n d scad (D eca p te ru s m a ru a d si, D . m a c ro so m a and D. m a c a re llru s), small tu n as ( T hunnus to n g g o l, E u th y n n u s a ffin is , A u x is th a za rd , K a tsu w o n u s p e la m is and S a r d a orien ta lis), anchovies ( E n cra sich o lin a spp. and S to lep h o ru s in d icu s) and sardines (S a rd in ella g ib b o s a and A m b ly g a s te r sirm) . N early sole catch o f certain species (i.e ., K a tsu w o n u s p e la m is , S a rd a o rien ta lis and D. m a ca rellru s) are yielded m erely from th e A ndam an Sea. In th e to ta l pelagic catch from each region, th ese reso u rces share a b o u t 7 8 -8 7 % in th e G u lf and 6 5 -8 9 % in the A ndam an Sea (Saikliang and B o o n rag sa, 1997). O th er p elagic fish species are bigeye scad (S e la r c ru m e n o p th a lm u s), hardtail scad (M e g a la s p is c o rd yla ), and king m ackerel (S c o m b ero m o ru s spp.) o f w hich th eir contribution to th e to ta l c atch is ab o u t 13-22 % and 11- 3 5 % in th e G u lf and th e A ndam an Sea, respectively.
5. F ish in g G rou n d and S easons
Fishing gro u n d o f small pelagic fish have b een expanded extensively o v e r inshore and offshore along th e coast, w h ere th e w a te r dep th is m o re th a n 20 m in th e G u lf and u p to 40 m in th e A n d am an Sea. In th e G u lf o f Thailand, th e fishing g ro u n d o f Indo-Pacific m ackerel is along th e w e ste rn co ast and th e u p p e r p art o f th e Gulf. F o r Indian m ackerel and sardine, the fishing g ro u n d is m ainly lo cated w ithin th e dep th range o f 30-70 m. R o u n d scads distribu te in offsho re area (d ep th o f w a te r m o re th a n 50 m) w hile small tu nas have w idespread distribution in th e w h o le Gulf, especially in the central part. A nchovies are m ainly caug ht in co astal w a te r along th e w e ste rn and eastern c o ast o f th e Gulf. T h e fishing season is all y ear ro u n d w ith th e m ajo r p eak during June to O c to b er ( S ou th w est M on so o n ) and a m inor p e ak during N o v em b er to M ay (Saikliang and B o o nrag sa, 1997). In th e A ndam an Sea, th e m ain fishing g ro u n d o f Indo-P acific m ackerel is lo cated in th e lo w er p art along th e coast. T he fishing gro u n d for Indian m ackerel is scattering along th e coast. T he fishing g ro u n d fo r ro un d scad is m ore o r less w id esp read along th e coast. Sardines and anchovies are w idely distributed in th e inshore and
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offshore along th e coast. T he fishing seasons is ap parent w ith th e p eak confined to N o rth e a st M o n so o n during N o v em b er to M ay (Saikliang and B oonrag sa, 1997).
6. P rod u ction and C atch R a te
G u lf o f Thailand: T he annual p ro d u ctio n s o f small pelagic fish caug h t by com m ercial fishing g ears from 1980-1994 indicated th e increasing trend from 2 8 6,1 0 9 m t in 1980 to 534,599 m t in 1991. T he tren d rises up to the p eak o f 6 7 5,9 04 m t in 1992 then d ro p s to 583,895 m t in 1993 and increases again during 1994-1995 (6 1 4 ,8 1 4 -6 6 1 ,6 8 6 m t) (Fig. 2 and Table 2). T he tren d is conform able w ith th a t o f the num ber o f registered p urse seines (Fig. 1).
A nnual c atch o f Indo-P acific m ackerel fluctuated and slight d ecreased from th e p e ak o f 99,638 m t in 1984 to 7 3 ,7 2 7 m t in 1994 and increased again in 1995 (105,323 m t). B y using m ackerel gill n e t (M E N ) as standard gear, th e C P U E show s th e sam e fluctu atio n as th a t o f pro d uctio n , excep t and u nusual lo w C P U E in 1986 and 1995.
P ro d u c tio n o f Indian m ackerel increased from 29,827 m t in 1984 to 38,803 m t in 1986 then d ecreased to th e lo w est catch o f 16,256 m t in 1991. T he catch increased again to th e p eak o f 49,231 m t in 1994. P u rse seiner is a standard gear. T rend o f catch ra te indicated th e sam e p a tte rn to th a t o f th e p rod u ctio n .
T he ro u n d scads c atch slightly decreased from 27,475 m t in 1984 to 23 ,9 4 7 m t in 1986 then increased abruptly to 4 1 ,8 3 8 m t in 1987, after th a t it expresses sharply d ecreased to th e low est p o in t o f 10,676 m t in 1990. It increased again up to th e p e ak o f 54,633 m t in 1995.
C atch ra te fluctu ates w ith decreasing tre n d fro m 1984 to 1990. T h e increasing tre n d is app aren t from 1990 46 k g/day to 1995 2 6 0 kg/day.
Small tun as p ro d u c tio n increased from 69,355 m t in 1984 to 156,208 m t in 1990. T h e highest p e ak o f catch w as 157,163 m t in 1992 and tend to decrease in th e follow ing years. T he catch ra te show s sim ilar tre n d as com pared to th e p roduction. T he m inim um and m axim um o f catch ra te are 330 k g/day in 1984 and 846 k g/day in 1991, respectively.
T h e catches o f anchovies m arkedly increased during 1988 -1992 (from 66,675 m t to 120,211 m t) and th e n declined to 115,718 m t in 1995. C atch ra te o f this species fluctu ated during th e p eriod o f 1984 to 1995, w ith th e lo w e st ra te o f 1,569 k g /day in 1987 and th e p e ak o f 6 ,282 kg/day in 1992.
P ro d u c tio n o f sardine slightly increased from 83,814 m t in 1984 to 137,965 m t in 1995 w ith th e p e ak o f c atch o f 141,422 m t in 1992. T h e tre n d o f catch ra te w a s sim ilar to th a t o f catch, except from 1994 to 1995.
T he p ro d u c tio n and catch ra te o f o th er pelagic fish species are p resen ted in th e T able 1.
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F ig. 2 T o tal ca tch o f pela gic fish ca u g h t by th e m ain fish in g gears in th e G u lf o f T h ailan d and A n d a m a n Sea, T h a ilan d , from 1980 to 1995.
A ndam an Sea: T he p ro d u c tio n and catch ra te o f pelagic species cau g h t by com m ercial fishing g ears show th e increasing tren d during th e p erio d o f 1984-1995 (Fig. 2 and T able 2).
A nnual c atch flu ctu ates w ithin a ran ge o f 59,960 - 3 0 9 ,8 3 4 m t. B y u sing p u rse seines as stan dard gears, annual C P U E show ed a flu ctuation b e tw een 1,790 and 4 ,0 11 kg/day.
P ro d u c tio n o f Indo-P acific m ackerel increased from 18,675 m t in 1984 to th e p eak o f 66,985 m t in 1993 and decreased d o w n to 46,945 m t in 1995. C atch ra te sh ow ed an increasing tren d b u t flu ctu ated in som e p eriod from th e lo w est o f 23 7 k g /d a y in 1988 to th e p e a k o f 994 k g /d ay in 1993.
R o u n d scad catch in overall view show ed increasing tre n d b u t greatly fluctuated b e tw ee n 2 ,4 6 4 m t (in 1986) and 35,99 4 m t (in 1994). T he annual C P U E sho w ed a sam e flu c tu a tio n as th e p ro d u c tio n tren d , w h ich varied from 102 to 646 k g /day during 1984 to 1995.
T h e annual p ro d u c tio n and C P U E o f small tu n as show ed an increasing tre n d w ith a g re a t flu ctu atio n in som e period, and p ro d u c tio n and catch ra te sho t u p nine tim es in 1995 th a n in l9 8 8 .
P ro d u c tio n o f sardine sh ow ed slightly decreased from 41,641 m t in 1987 to 20,893 m t in 1992 and th e n increased abruptly to th e p e ak o f 54,849 m t in 1995. A nnual C P U E indicated a sam e tre n d as p ro d uctio n . R ange o f C P U E varied fro m 337 to 1,162 kg/day during 1984 to
1995.
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Speciesname/year198419851986198719881989199019911992199319941995Standard gear Indopacificmackerel Total catch(mt)99,63897,85288,76892,15588,82292,68868,16055,18688,30868,02573,727105,323 Catchrate(kg/day)7311,0672751,0761,0191,1426121,4501,2424001,338574MEN Indianmackerel Total catch(mt)29,82732,86238,80336,25918,65326,49820,84416,25629,33733,88249,23143,697 Catchrate(kg/day)187240213185611225886108140278165SEINE Roundscads Total catch(mt)27,47525,66723,94741,83814,01517,26710,67622,74742,52546,28638,39454,633 Catchrate(kg/day)1852061442597310246149181237254260SEINE Smalltunas Total catch(mt)69,35581,20090,22596,131141,274124,899156,208137,869157,163106,79799,81186,863 Catchrate(kg/day)330489426495651681626846617491600355SEINE Anchovies Total catch(mt)88,804103,10157,95955,46665,67594,315118,727110,020120,211116,64897,343115,718 Catchrate(kg/day)2,7222,1001,8081,5691,8951,8141,7542,1196,2824,6772,6801,219APS Sardines Total catch(mt)83,81468,44792,52783,63389,077114,31090,789114,465141,422112,620123,700137,965 Catchrate(kg/day)494520523430410624360730583575795634SEINE Kingmackerel Total catch(mt)8,0998,38010,97811,92412,0509,1819,1536,1106,7119,5638,5379,258 Catchrate(kg/day)899399928278838783949884KMG Bigeyescad Total catch(mt)23,06117,17418,72822,97811,93112,06319,97215,45121,85119,58137,08036,449 Catchrate(kg/day)152136112135526074908795230163SEINE Source: 1984to1994(SaikliangandBoonragsa, 1997);1995(DOF, 1998b)
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Table 1: Total catches and catch rates of commercial important pelagic fish in the Gulf of Thailand from 1994 - 1995.
Table 2: Total catches and catch rates of commercial important pelagic fish in the Andaman Sea 1984 - 1995 Standard gear SEINE SEINE SEINE SEINE SEINE Source: 1984 to 1994 (Saikliangand Boonragsa, 1997); 1995 (DOF, 1998 b)
1995 46,945 731 22,981 443 42,611 802 54,849 1,041 277,957 4,011
1994 65,499 715 35,994 520 31,182 440 29,455 418 309,834 2,916
1993 66,833 994 8,984 143 40,784 634 38,440 596 243,176 2,835
1992 32,863 667 8,434 194 11,903 247 20,893 450 140,969 2,029
1991 38,616 461 23,982 335 14,256 187 24,167 337 176,794 1,888
1990 25,127 378 i______ 22,559 352 6,883 99 27,375 427 146,281 2,152
1989 17,487 366 22,330 494 4,695 94 29,186 632 121,646 2,397
1988 12,044 237 17,747 359 4,845 89 32,619 660 98,912 1,790
1987 15,029 362 14,276 336 6,261 146 41,641 905 120,563 2,263
1986 13,766 548 2,464 102 3,392 124 26,604 1,098 59,960 2,316
1985 13,757 593 8,025 373 5,594 251 27,545 1,162 67,852 2,754
1984 18,675 507 16,777 646 7,369 269 30,563 995 90,846 2,812
Species name/year Indo pacificmackerel Total catch(mt) Catch rate (kg/day) Round scads Total catch (mt) Catch rate(kg/day) Small tunas Total catch(mt) Catchrate(kg/day) Sardines Total catch(mt) Catch rate (kg/day) TotalPelagic Total catch (mt) Catchrate(kg/day)
7. T h e S ta tu s o f Pelagic R esources and F isheries
T h e p elagic fishes re so u rces in T hai W aters have been intensely fished during th e past tw o decades. This is p articu lar fo r th e situation o f b o th Indo-P acific m ackerel and sm all tunas, ones am ong th e m o st econom ically im portant species caught in the G u lf o f Thailand and th e A ndam an Sea. P u rse seine is th e m ost effective g ear used fo r catching th ese ta rg e t species, w h e rea s it is also th e m u ltip urp o se gear used fo r catching pelagic fishes in general. T herefore, this cau ses different effect on each stock and fishing ground. F rom th e G u lf o f Thailand, C hullasorn (1 9 9 8 ) re p o rte d on th e annual production, catch rate o f standard gear, and standard fishing effort fo r small pelagic fish during 1972-1994. By applying Schaefer and F ox m odel to estim ate th e m axim um sustainable yield (M S Y ) and th e optim um fishing effort, th e results
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Species Catch from 1984-1995 (mt)
Average (mt)
MSY (mt)
Indo-Pacific mackerel1 55,186-105,323 84,888 84,500
Indian mackerel2 16,256-49,231 31,346 32,000
Round scads2 10,676-54,633 30,456 49,000
Small tunas2 69,355-157,163 112,316 111,000
Anchovies2 55,466-120,211 95,416 106,000
Sardines2 68,447-137,965 104,397 117,400
King mackerel2 6,110-12,050 9,162 12,400
Bigeye scads2 11,931-37,080 21,360 21,500
Pelagic fish2 286,109-661,686 500,247 594,400
Species Catch from
1984-1995 (mt)
Average (mt)
MSY (mt)
Indo-Pacific mackerel1 12,044-66,833 30,553 23,765
Round scads1 2,464-35,994 17,046 15,728
Small tunas1 4,695-42,611 14,982 8,651
Sardines1 19,874-54,849 31,945 31,641
Pelagic fish1 56,474-286,509 154,566 136.602
show ed th a t m ostly small pelagic fish have b een over-fished, except hardtail scad and king m ackerel (T able 3). F o r th e la tte r species, this m ay be because they are w idely m igratory species w hile th e re is no high effective gear fo r catching them . As notified in the re g istra tio n o f C PS, th e n um ber o f g ears d ecreased in 1973 and th ere w as no m ore reco rd since 1977. This is because th e fisherm en have m ade changes and subsequently registered th eir g e ars in a n o th er ty p e o f p u rse seine. Including fishing g ro u n d o f this g e ar has also b een dim inished by o th e r g ears d estructio n. C hullasorn (1 9 9 8 ) re p o rte d on th e situ atio n o f fisheries and sho w ed overfishing ten d en cy as re sp ec t to th e num ber o f fishing effort (num ber o f vessel) o f T P S , LPS and FA D . T o w a rd th e so lu tion o f this crisis, C hullasorn (1 9 98) suggested th a t perm ission o f th e n e w license fo r p u rse seiner should be lim ited and enforcem ent a decreasing o f n u m ber o f vessel is 2 0 p e rc en t fro m to b e reg istered a t present. In th e A ndam an Sea, th e sto ck o f In d o - Pacific m ackerel, w h ich lo cated in th e lo w er p a rt o f th e coast, and banded trevally (A tu le m a te ) indicated overfishing. A t th e sam e tim e, th e reco v ery o f this stock seem s to b e im proved. F o r Indian m ackerel, ro u n d scad, sardines, small tunas, hardtail scad and bigeye scad have no definite th e sign o f over-fished (T able 4). B esides th e form er results th a t sh ow ed be useful considered concerning th e status o f pelagic reso u rces and fisheries in th e A ndam an Sea such as th e lim ited o f fishing k no w led g e and efficiency o f g e ar fo r Thai fisher into offshore fishery.
A nd, changing o f ta rg e t species o f pelagic fisheries have co ntrolled by th e statu s o f re so u rces and econom ic dem and. T he decreasing o f fishing effort during S o u th w est m o n so o n is a result o f ro u g h sea. In addition, small pelagic fish are w idely m igratory species. They have a b e tte r chance to escape fro m one fishing gro u n d to another. B ase on th ese evidences, th e statu ses o f pelagic re so u rces are satisfactory in th e A ndam an Sea (B o o n rag sa and B oo nsu k, 1998).
Table 3 Catches and maximum sustainable yield of important pelagic species in the Gulf of Thailand.
Remarked: 1 = Chullarson, 1998 and MEN is standard gear by Schaerer's model.
2= Chullarson, 1998 and PS is standard gear by Schaefer's model.
Table 4 Catches and maximum sustainable yield of important pelagic species along the Andaman Sea.
Remarked: 1 = Bhatuyasevi, 1997 and PS is standard gear by Schaefer's model
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8. M A N A G E M E N T O F T H E P E L A G IC F IS H E R IE S
M any g ro u p s o f small pelagic fish have b een subjected to fully ex p lo itation and m ay be over-fished. T his is b ecau se th e rapid developm ent and expansion o f pelagic fisheries have been in th e G u lf o f T hailand and th e A ndam an Sea during th e last tw o decades. It seem s th a t th e ro o m fo r fu rth e r fishery d evelopm ent is very scarce. M any scientists have re p o rte d th e ir statu s and p ro p o se d to se t u p an a p p ro p riate m easu re to conserve, m anage and co n tro l fishing o p e ra tio n w ith a v iew to harm onize fishing activities fo r th e available po ten tial resou rces. It is a k n o w n fa c t th a t w ith o u t system atic m anagem ent, m onitoring, control, surveillance and rehabilitation, it w ill lead to g re a te r conflict in th eir use. In o rd e r to co n serve th e m arine fishery reso u rces, th e D O F o f T hailand has set u p v ario u s m anagem ent m easures th ro u g h th e Fisheries A ct o f 1901 w h ich w a s co n sequently revised in 1947 and 1982 (Saikliang and B o o n rag sa, 1997). T h e reg u latio n s have b een issued, w ith th e objective o f conserving m arine fishery reso u rce s, include: determ ination o f th e size and kinds o f fishing im plem ents th a t are p erm itted in fisheries; prohibiting th e u se o f certain ty pes o f fishing m eth o d o lo g y in certain areas;
establishing spaw ning and nursing seasons and areas o f m arine re so u rce s and prohibiting th e u se o f certain ty p es o f fishing g e a r during th e re seaso n and areas; m esh size re g u la tio n fo r p u rse seining, gill n ettin g and lift netting; lim iting th e new entry o f tra w l and pelagic fisheries and ceasing to g ra n t n ew tra w l and p u rse seine licenses.
In th e case o f P h a n g -n g a B ay, th e co n servatio n m easures hav e established fo r th e p ro h ibit fishing o f tra w le rs and p u sh n e tte rs w ithin a distance o f 3 ,000 m in all y e ar since 1979.
F o r th e b reed in g o f In d o Pacific m ackerel have b e en p ro te c te d by closed seasons since 1985. In addition, th e fisheries p a tro l h av e strictly o n g u ard and fisher folk w h o alive surro u n d in g in th e B ay have also established th e self-enforcem ent and im plem ent since 1 99 3 (C h antaw o ng e t a l., 1996). A fter th a t th e p ro d u c tio n o f m arine reso u rces, especially Indo Pacific m ackerel, has increasing fro m 300 k g /d ay in 1992 to 916 k g/day in 1997 cau gh t by pu rse seiner (B o o n ra g sa e t a l., 1998).
8. C O N C L U S IO N A N D R E C O M M E N D A T IO N
T h e annual p ro d u c tio n o f small pelagic fish in th e G u lf o f Thailand and th e A ndam an S ea varies from 2 8 6 ,1 0 9 to 6 75 ,90 4 m t and 10,800 to 3 0 9,8 34 m t, respectively during 1980- 1995. It shared ab o u t 33 p ercen t in to ta l c atch o f b o th C oasts. T oday, th e p ro d u ctio n s o f small pelagic fish are up 2 tim es in th e G u lf and 26 tim es in th e A ndam an Sea, w hich co m p ared from th e pelagic p ro d u c tio n in 1980. M ain species o f small pelagic fish caug ht in Thai W aters are In d o-P acific m ackerel, Indian m ackerel, ro u n d scad, small tu nas, anchovies and sardines. P u rse seine is th e m ain fishing g ears fo r catching small pelagic fish in T hai W aters, th a t consisted o f L P S , T P S , T U N , G PS, FA D , C PS and A PS o p erated extensively ov er th e inshore and offshore alo ng th e coast. T h e fishing g ro u n d s are average dep th o f sea is m o re th a n 20 m in th e G u lf and m o re th a n 40 m in th e A ndam an Sea. T he fishing season have cau g h t o v er th e w h o le year, w hich th e p e a k consid ered to be high during th e S ou th w est M o n so o n in th e G u lf and N o rth e a st M o n so o n in th e A ndam an Sea.
R esu ltin g fro m th e rapid developm ent and expansion o f pelagic fisheries, it has effected a g re a t p re ssu re o n th e available reso u rces in Thailand. It is clear th a t alm ost all o f pelagic fish sto ck s h av e b een fully exploited and som e sto ck are subjected to overfishing. T he catch co m p ositio n is changing to w a rd sm aller size o f fishes and less in values as clearly observed in sardine sto c k th a t over 4 0 % have been used fo r fish m eal p ro d u c tio n due to small size and u n accep tab le fo r caning factories (Saikliang and B o on rag sa, 1997). It is an ticipated th a t this situatio n will be continued in th e fu ture if an ad eq u ate coun term easu re fo r fishery m anagem ent, re so u rce co n servatio n and utilization have n o t been undertaken.
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