Stock Assessment of Oceanc Tuna n South Chna Sea off Sarawak and Sabah Malaysa. Fsheres Research nsttute Malaysa Sarawak Branch PG.Box 2243 93744 Kuchng Sarawak. Malaysa. Abstract.-Catch data of a commercal purse sener operatng n South Chna Sea off Sarawak and Sabah were analyzed to determne the speces composton dstrbuton fshng ground abundance productvty level and bomass of oceanc tuna. t was found that the catch of oceanc tuna per trp ranged from 80.0 to 400.0 tonnes wth an average of 23.8 tonnes and the trp duraton was between 7 and 27 days. The catch rate of oceanc tuna ranged from 2.4 to 52.8 tonneslhaul and regstered an average of 0.9 tonnes/haul. The catch of skpjack (Katsuwonus pelams) and yellowfn (Thunnus albacares) per trp ranged from 55.0 to 369.4 tonnes (average of 55. tonnes) and 20.0 and 62.0 tonnes (average of 70.4 tonnes) respectvely. The catch rate of skpjack ranged from.8 to 52.8 tonneslhaul wth an average of 7.9 tonneslhaul whereas for yellow fn t was between 0.6 and 7.4 tonneslhaul and averaged at 3.0 tonneslhaul. The speces composton of the total catch comprsed 72.5% skpjack and 27.5% yellowfn. Skpjack and yellowfm were dstrbuted all over the deeper waters of Sarawak and Sabah however the man fshng ground were areas around North Lucoma Shoal Lousa Reef Royal Charlotte Reef Swallow Reef Amboyna Cay Barque Canada Reef and Erca Reef. The most productve areas were Barque Canada Reef Erca Reef and Amboyna Cay where the catch rate was over 50.0 tonnes/haul. The densty of oceanc tuna ranged from 2.5 to 22.8 tonnes/n.m. 2 wth an average of7.6 tonnes/n.m. 2. The total bomass of oceanc tuna over the study area of 39600 n.m. 2 was estmated at 299790 tonnes. of )ck 90. of Abstrak.-Data tangkapan sebuah kapal pukat jerut komersal yang beroperas d Laut Cna Selatan d peraran Sarawak dan Sabah telah danalsa dengan tujuan untuk menentukan komposs spess taburan kawasan penangkapan kan kepadatan tahap produktvt dan bomas kan tuna lautan. Adalah ddapat bahawa tangkapan kan tuna lautan bag setap pejalanan alah dalamjulat darpada 80.0 sehngga 400.0 tan dengan purata 23.8 tan dan tempoh trp d antara 7 dan 27 har. Kadar tangkapan tuna lautan alah dalam d antara julat darpada 2.4 sehngga 52.8 tan/operas dan mempunya purata 0.9 tan/operas. Tangkapan kan tuna skpjack (Katsuwonus pelams) dan yellowfm (Thunnus albacares) alah masngmasng dantara 55.0 dan 369.4 tan/pejalanan (purata 55. tanlpejalanan) dan d antara 20.0 dan 62.0 tan/pejalanan (purata 70.4 tanlpejalanan). Kadar tangkapan skpjack alah dalam julat.8 sehngga 52.8 tanloperas dengan purata 7.9 tan/operas manakala untuk yellowfm kadar alah dantara 0.6 dan 7.4 tan/operas dengan purata 3.0 tan/operas. Komposs spess tangkapan terdr darpada 72.5% skpjack dan 27.5% yellowfn. Skpjack dan yellowfn adalah ddapat d keseluruhan peraran laut dalam Sarawak dan Sabah. Walaubagamanapun kawasan utama penangkapan kan alah d kawasan sektar North Lucona Shoal Lousa Reef Royal Charlotte Reef Swallow Reef Amboyna Cay Barque Canada Reef dan Erca Reef. Kawasan yang sangat produktf alah Barque Canada Reef Erca Reef dan Amboyna Cay dmana kadar tangkapan adalah melebh 50.0 tanloperas. Denst kan tuna lautan adalah dalam julat 2.5 sehngga 22.8 tanln.m. 2 dan mempunya purata 7.6 tanln.m. 2. Jumlah bomas kan tuna lautan d kawasan kajan yang seluas 39600 n.m. 2 telah danggarkan sebanyak 299790 tan.
The Exclusve Economc Zone (EEZ) of Malaysa that stretches across the South Chna Sea offers great opportuntes for the development of offshore fsheres. The Department of Fsheres encourages the development of offshore fsheres n order to reduce ntensve fshng effort n the nshore waters. Oceanc tuna s one of the target speces that could be further exploted especally off the coast of Sarawak and Sabah; At the moment there s only one commercal purse sener operatng n the offshore waters of Sarawak and Sabah. The purse sener EBONY LADY (EL 326405) s a steel-hull vessel 5.0 m n length 0.6 m n breadth and 5.0 m n depth. The 779.28 GRT vessel s powered by a 2200 h.p. desel engne. The purse sene net used n the fshng operaton s 200 m long and 00 m deep wth.5-6.0 cm mesh sze. The purse sener s operated n conjuncton wth lures or fsh aggregatng devces (FADs). The use of FADs facltates fshng efforts by concentratng the fsh n a partcular area. Several FADs were nstalled along trenches (mostly over a 00 fathoms n depth) and as near as possble to the reefs. Ths takes nto account the tendency of tuna to be assocated wth reefs. The other types of fsh school targeted are those found around drftng logs and those assocated wth brds. Ths study on oceanc tuna resources n Sarawak and Sabah waters was conducted n 995. The objectve of ths study was to assess the resources of oceanc tuna n terms of ther speces composton dstrbuton fshng ground abundance productvty level and bomass. The catch and effort data of the commercal purse sener and the nformaton on the vessel were obtaned from Labuan's Fsheres Department. The data had been recorded n the catch and effort data sheet. The total landngs number of fshng trps number of fshng days and number of hauls of the purse sener operatng snce February 992 to March 995 were extracted for data analyss. n the data analyss the overall catch rates (catch per haul) were obtaned by dvdng the total catch wth the number of hauls. The catch rate by speces was calculated by dvdng the total catch of each speces wth the number of hauls. The catch rates were obtaned for all the months of fshng operaton. To determne the average catch rates of each fshng grd (.e. 30 n.m. by 30 n.m.) the total catch were dvded by the number of hauls wthn that partcular grd. The speces composton was determned by takng the rato of skpjack to yellowfn. The dstrbuton of the productve ground for skpjack and yellowfn was dentfed based on the catch rates dstrbuton. Estmaton of fsh densty was based on the fndngs that yellowfn were consdered to be assocated wth fsh aggregatng devce (FAD) f they were caught wthn.6 km (or 0.86 nautcal mles) of FAD buoy (Buckley et al. 989). The area delneaton for FAD (.e. <.6 km) was based on the observed behavor of FAD assocated schools of tuna to reman relatvely close to the buoy durng the day. Calculaton of the densty of ndvdual grd was by dvdng the catch rate wth the area wthn 0.86 nautcal mles radus of FAD buoy. Bomass per grd was calculated by multplyng densty wth the area of the grd (.e. 900 n.m. 2 ). The bomass of the fsh n the study area was estmated by summng up the bomass of ndvdual grd.
Results Catch and Effort The catch data of the purse sener operatng n Sarawak and Sabah waters are shown n Table. A total of 8 fshng trps were made n the waters ofsarawak and Sabah snce February 992 untl March 995. The duraton of each trp ranged from 7 to 27 days wth an average of 6 days per trp. For each trp the number of fshng ope~atons was between 7 and 55 hauls wth an average of 9 hauls/trp. Durng these trps a total of354 hauls were carred out wthn 44 grds of30 n.m. 2 each (.e. coverng an area of39000 n.m. 2 ) rangng from to 8 hauls/grd square. Table : ndex of catch for a commercal purse sener Ebony Lady from 992 to 995 Date No. of trp Catch (tonne) Total catch Fshng No. of hauls Catch rates (tonne/haul) (tons) Skpjack YeUowfn Days Total Skpjack Yellowfn Feb '92 369.4 369.4 7 7 52.8 52.8 Mar '92 96.0 96.0 5 8 24.5 24.5 Apr '92 96.0 00.0 96.0 23 4 4.0 6.9 7. May '92 96.0 04.0 200.0 6 4 4.3 6.9 7.4 lull '92 26.0 26.0 9 9 4.0 4.0 Aug '92 84.0 23.0 07.0 0 9 5.6 4.4.2 Apr '93 238.0 62.0 400.0 27 55 7.3 4.3 2.9 lull '93 96.7 43.3 240.0 22 30 8.0 3.2 4.8 30 '94 60.0 20.0 80.0 5 33 2.4.8 0.6 Mar '94 20.0 40.0 60.0 6 20 8.0 6.0 2.0 May '94 55.0 75.0 30.0 9 3 0.0 4.2 5.8 lun '94 5.0 70.0 85.0 6 20 9.3 5.8 3.5 lul '94 75.0 40.0 5.0 6 20 5.8 3.8 2.0 Sep '94 205.0 50.0 255.0 9 24 0.6 8.5 2. lall '95 50.0 54.0 204.0 8 7 2.0 8.8 3.2 Feb '95 250.0 00.0 350.0 20 2 6.7.9 4.8 Mar '95 250.0 55.0 305.0 4 2.8 7.9 3.9 Mar '95 20.0 20.0 230.0 4 6 4.4 3..3 Overall catch rates The analyss showed that the total catch of tuna per trp ranged from 80.0 to 400.0 tonnes wth an average of23.8 tonnes. The overall average catch rates of tuna ranged from 2.4 to 52.8 tonneslhaul wth an average of 0.9 tonneslhaul. The catch of skpjack and yellowfm per trp ranged from 80.0 to 369.4 tonnes/trp (average of 55. tonnes) and ranged from 20.0 to 62.0 tonnes/trp (average of 70.4 tonnes/trp) respectvely. The catch rates of skpjack ranged
from.8 to 52.8 tonneslhaul wth an average of7.9 tonneslhaul. As for yellowfn the catch rates were between 0.6 and 7.4 tonnes/haul wth an average of 3.0 tonnes/haul. Speces composton The catch comprsed of only two speces of oceanc tuna that s skpjack (Katsuwonus pelams) and yellowfm (Thunnus albacares). Skpjack was the most domnant speces formng about 72.5% of the total catch and yellowfn contrbutng the remander 27.5%. Dstrbuton and productvty level of oceanc tuna Skpjack are present n all the catches of the purse sener but yellowfn were mssng from the catches of February March and June 992. The range of catch rates of tuna vares from grd to grd as shown n Fg.. The overall average catch rates of tuna wthn ndvdual grd are as shown n Fg. 2 and t ranged from 5.9 to 52.8 tonneslhaul. The productvty levels of oceanc tuna were grouped nto four categores n terms of ther average catch rates (Fg. 3). Catch rates offsh between 5.0 and 0.0 tonneslhaul were mostly found n areas around Lousa Reef. Catch rates that ranged from.0 to 20.0 tonneslhaul were found all over the deeper waters of Sarawak and Sabah. However most of these catches were obtaned n areas around Swallow Reef Royal Charlotte Reef and north of Labuan and Kota Knabalu. Catch rates between 2.0 and 30.0 tonneslhaul were obtaned n areas adjacent to Amboyna Cay. Catches n areas around Barque Canada Reef Erca Reef and Amboyna Cay regstered a catch rate of over 50.0 tonneslhaul. Densty and Bomass Estmaton The densty of oceanc tuna by grd ran~ed from 2.5 to 22.8 tonnes/n.m. 2 as shown n Fg. 4. The average densty was 7.6 tonnes/n.m.. The bomass of oceanc tuna by each grd ranged from 2250 to 20520 tonnes (Fg. 5) and has an average of 683 tonnes per grd of900 n.m. 2. Based on the total area of study.e. 39600 n.m. 2 the bomass of oceanc tuna was estmated to be 299790 tonnes. The commercal purse sener regstered an average catch rate of 0.9 tonneslhaul and ths was comparatvely smlar to that recorded by the department's research vessel K.L. PADS.e. 8.9 tonneslhaul fshng n the same area (Mansor and Hamd 997). The K.L. PADS used a slghtly smaller and shallower purse sene net wth dmensons of 650 ll long 80 m deep and 0 cm n mesh sze. Skpjack and yellowfn were the only two speces of tuna found n the catch. Ths ndcates that skpjack and yellowfn does co-exst n a school. Ths fndng confrms the observaton by Hadl and Rchard (99) that yellowfn schools were frequently assocated wth skpjack n Sarawak waters. n the present study the catch percentage proporton of skpjack to yellowfn was found to be 72.5% to 27.5%. Ths s qute smlar to the observaton made by Mansor and Hamd (997) where skpjack and yellowfn formed 76.4% and 9.9% of the total catch respectvely. Skpjack and yellow fn are dstrbuted all over the deeper waters of Sarawak and Sabah. Oceanc tuna speces are caught n great quanttes n areas more than 60 nautcal mles from the shore of Sarawak. n Sabah waters skpjack are caught more frequently due to the deepsea condtons found closer to the shore (Hamd 987). Catches n areas around Barque Canada
09 9"< 8'< L on 5'< --- ; -+-l : ~~. vj;~.""./ 52.8..tgalor-can~ \ -+-.---t / (). 52.8 reef '<eef \ 'f =;t2 : ~Cna~l ()Erca~ ~ ~;~2.8 :;(; -r;2~y" h;e\es ~t)v C4'''Tl~ :2.0.~t~:L.--."._....-L- L ----+ () '( _~ ".6-24.5 4.0 4.3. : 4.4 6.".Pj: "......; () (2) (). :). ' () () \ - ~. L ' "Roya.O>arlott. ~';;f-j-. 'V~ "' :: 24.5 p.6-4.0 5.a-a.0 '5.6-24.5'5.6-4.0: 4.4-". 0.6 d.-----" ; () (2) (2) (4) (J) '(2) () B: ""~s ref"--:---' t.--------------f.ll---.- -.----f-. :':"'_'.7.-... ~...:. _ : j: 24.5 Swau reefc -r 6.' p.6-2.8 / ~ } (8) (2\ () (3).t: -_ '~5.6-24. KOTA KlNABALU.\ 4. - t;' f'-"'c::-~ (l) '~ \N. w: NA SKl.lS '. '. lo2j l/". J')l"\ t~o.o 2 4-~~\;a =~ 0.6 (t' 0 (8) ~;~ 2.0-. ' g;rbuan ----... ~ '\ " j 4.4 ". J 0. ; () s. llmf-. SllAl.S.:;. "... :.:..../.(.'}. -. - ~~ SA B A H /_td"".. --// 4.4 2.8 9.3.'. /-~.' -; \. ; (l) () () \\ ~RU"E ~ \.\ :'.;.F..--... /..-.~~-_... ;;;.""'-...~"'r";f '2~:8' '~;-:8- ' '... ' 'Ft.-re' () () V (' 0.6 ) () \ " 2 0 E ON : 8 "N : "N 0. en... 6 0 (') X ;J> en en 5 'N t en en ~ z... "N 0 4.4 'Tj... () 2.0 ~ ()."N
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Reef Erca Reef and Amboyna Cay regstered catch rates of over 50.0 tonneslhaul and were consdered as very productve. t appears that the man fshng grounds for oceanc tuna are n areas around North Lucona Shoal Lousa Reef Royal Charlotte Reef Swallow Reef Amboyna Cay Barque Canada Reef Erca Reef and north of Labuan and Kota Knabalu. Ths s because tuna resources are confned only to the hgh salne water around reef complexes as noted by Hadl and Rchard (99). Furthermore larvae of yellow fn had been found n areas adjacent to the Swallow Reef (Boonragsa 987). n fact skpjack and yellowfn were found mostly towards the northeastern part of Sarawak waters whch are adjacent to the southern part of Phlppnes waters (Sulu Sea) and the northeastern part of ndonesan waters (Celebes Sea). Accordng to Hampton (993) catches from these Phlppnes and ndonesan waters were predomnantly skpjacks and yellowfns. Tuna are hgwy mgratory speces and renders them qute dffcult to assess. However ths study provdes ntal nformaton on the dstrbuton man fshng grounds and estmates of productvty level and bomass of oceanc tuna n Sarawak and Sabah waters. A more comprehensve study should be carred out n future where a seres of catch and effort data for longer perods of tme are avalable. Meanwhle t s recommended that more commercal purse seners should venture nto the tuna fsheres snce the resource has hardly been exploted. The author wsh to express my sncere grattude to Y.Bhg. Dato' Mohd. Mazlan bn Jusoh the Drector General of Fsheres Department of Malaysa Mr. Junadb. Che Ayub the Drector of Marne Fsheres Department of Sarawak and Mdm. Faazaz bt. Abd. Latff the Chef of Fsheres Research nsttute of Malaysa Sarawak Branch Kuchng for ther encouragements and nvaluable support n conductng ths study. My deep apprecaton also goes to Mr. Henry Opang Luhat the former Chef of Fsheres Research nsttute of Malaysa Sarawak Branch Kuchng for hs support n carryng out the study and n preparng ths paper. My sncere' apprecaton also goes to Mr. Albert C. Gambang and Mr. Hadl Rajal for ther crtcal comments on the paper. Boonragsa V. 987. Tuna resources n the Tha waters Andaman Sea. n: Collectve volume of workng documents presents at the Expert Consultaton on Stock Assessment of Tunas n the ndan Ocean Colombo Sr Lanka 4-8 December 986. ndo-pacfc Tuna Development and Management Programme 267-280. Buckley R. M. tano D. G. and Buckley T. W. 989. Fsh aggregatng devce (FAD) enchancement of offshore fsheres n Amercan Samoa. Bulletn of Marne Scence 44(2): 942-949. Hadl R. and Rchard R. 99. Dstrbuton and bologcal status of the pelagc resources of Sarawak Malaysa. Fsheres Bulletn No. 68. Department of Fsheres Mnstry of Agrculture Malaysa. 23 p.
Hamd A. Y. 987. Tuna fsheres n Sarawak and Sabah. n: Report of the Second meetng oftuna research groups n the Southeast Asan Regon Manla Phlppnes 25-28 August 987. ndo-pacfc Tuna Development and Management Programme. Hampton J. 993. A revew of tuna fshery-nteracton ssues n the Western and Central Pacfc Ocean. n: nteractons of Pacfc tuna fsheres. Proceedngs of the Frst FAa Expert Consultaton on nteractons of Pacfc Tuna Fsheres edted by R.S. Shomura J. Majkowsk and S. Lang 3- December 99. Noumea New Caledona. Volume : Summary report and papers on nteracton. FAD Fsheres Techncal Paper No. 336 Vol. Rome FAa 993.326 p. Mansor M.. and Abd. Hamd Y. 997. On bologcal aspects of skpjack Katsuwonus pelams and yellowfn Thunnus albacares off the Sarawak waters. Fsheres Bulletn No. 06. Department of Fsheres Mnstry of Agrculture Malaysa.