C.M.l978fJt:~34... I -"1-

Transcription

1 This ReEort not to be cited without Erior reference to th~\cou~cilx) nternational Council\for the Exploration of the Sea _,t ) ',d~' C.M.l978fJt:~ "- Pelagic Fish 8ommfttee~~ REPORT OF THE BLUEFN TUNA WORKNG GROUP Observations on the Size Composition of Bluefin Tuna Catches from 977 Edited by: H Aloncle, E Bakken, J Rodriguez-Roda and K Tiews This Report has not yet been approved by the nternational Council for the Exploration of the Sea; it has therefore at present the status of an internal document and does not represent advice given on behalf of the Council. The proviso that it shall not be cited without the consent of the Council should be strictly observed. x) General Secretary, CES, Charlottenlund Slot, DK-2920 Charlottenlund, Denmark.

2 REPORT OF THE BLUEFN TUNA WORKNG GROUP Contents Pa~ ntroduction l Material l Results 5 References 7 Tables 22 9 Figures o-o-o-

3 - - ntroduction Reference is made to previous reports of the Bluefin Tuna Working Group (Statistical News Letters, NQ 20, 36 and 38, to Cooperative Research Reports, Ser. A., NQ 23, 40 and 7 as well as document c 0 N J: 3. n 977 Mr. J. Hamre from the nstitute of Marine Research in Bergen, member of the Working Group since its beginning in 96, decided to withdraw because of too many other obligations and was replaced by Mr. E. Bakken of the same institute. Other Working Group members are at present Dr. P. les (Canada), Dr. H. Aloncle (France), Prof. K. Tiews (Federal Republic of Germany) (Chairman), Mrs. 0. Moura (Portugal), Dr. J. Rodriguez-Roda (Spain), Mr. R.C. Hennesmuth (USA) and Dr. James C. Tyler (USA). The members continued their work by correspondence and with other tuna research workers in the region. The data obtained for the fishing season 977 are presented in the following. Material Data on the size and age composition of Bluefin tuna catches were received from the following countries: Canada (Tables -4), Denmark (Table 5), France (Table 6), Norway (Table 7), Portugal (Table 8), Spain (Tables 9-3) and USA (Tables 4-8). Mrs. C.D. Burnett, Mr. P.C.F. Hurley and Dr. T.D. les reported that the-canadian landings of bluefin tuna in 977 for the west Atlan cic yielded 972 metric tons round weight (Table ), an increase of 26 mt or 3 % over the previous year: a) The purse seine fishery for juveniles off the eastern coast of the United States accounted for 298 mt, a decrease of 34 mt ( o%) from 976. b) The trap fishery in St. Margaret's Bay, Nova Scotia, took 368 mt of giant bluefin, an increase of 200 mt or 9 % over the previous year. c) The sport (rod and reel) fishery for giant bluefin declined from 342 mt in 976 to 302 mt in 977.

4 - 2 - Regulations introduced in the Canadian bluefin fishery in 974 have been maintained, subject to minor modifications in 975 and 976. Weights were obtained for 577 of the 78 large bluefin taken in five locations along the :~nadian Atlantic coast (Table 2). Mean weights rangeftom to 437. kg. The size composition of monthly Prince Edward sland rod and reel landings is presented in Table 3. The average weight of fish increased as the season progressed, from kg in August to kg in October; the seasonal average was kg, approximately the same as 976. The Canadian purse seine fishery for small bluefin took 298 mt. This fishery operated during July and August off the New York-New Jersey coast of the United States in 977. The size (fork length) composition of this catch is presented in Table 4. Fork lengths range from 44.5 to 63.6 cm, with an average length of 6.2 cm. n addition, 50 otoliths were extracted for age determination and several vertebrae and gonad samples were taken. n 977, ten giant bluefin were tagged and released: nine from the Bay of Chaleur area (Gulf of St. Lawrence) and one east of Halifax, Nova Scotia. Five tagged bluefi.n were recovered in 977; two fish were recaptured in the Gulf of Mexico from fish tagged in St. Margaret's Bay and in the Bay of Chaleur in 976; and bluefin tagged in the Bay of Chaleur area in 973, 975 and 976 were recaptured in the same general area. The commercial impoundment program in St. Margaret's Bay was increased to 8 impoundments in 977, and 77 giant tuna were successfully fattened for the Japanese market. n September, 290 fish were removed (average weight 393,2 kg) and in October, 427 fish were recovered (average weight 44.0 kg). One impoundment containing 3 giant bluefin was allocated for experimental purposes in St. Margaret's Bay. Canadian and U.S. scientists worked in a co-operative program involving studies of:

5 - 3 - internal body temperature, ambient water temperature and depth of free-swimming fish using ultrasonic telemetry; feeding behaviour; nutrition; tag retention; sex determination by hormone radioimmunoassay; aging validation; and tissuecontaminant analysis. Sampling of otoliths for age determination was continued with approximately 270 giant bluefin sampled in three different areas, in addition to the fifty juvenile bluefin sampled in the purse seine fishery. On the recommendation of the Standing Committee for Research and Statistics (CCAT), a bluefin tuna aging workshop was held in New York in March, 977. Scientists from several nations discussed existing aging techniques in an effort to standardize these procedures. The Proceedings of the workshop have been presented to the CCAT Secretariat for distribution and a second workshop is planned for 978. As a result of the 977 workshop, an experiment involving the administration of tetracycline to impounded giant bluefin in St. Margaret's Bay, up to 2 months prior to slaughter, was initiated to validate present aging procedures. Otoliths and vertebrae from these fish are presently being analyzed. The following papers were presented to CCAT's Standing Committee on Research and Statistics in November 977: ) Butler, -. J.A.: 2) Butler, J.J.A., The St. Margaret's Bay (Nova Scotia) Bluefin Research Program: A Progress Report (SCRS/77/89). and T.G. Pincock: The Ultrasonic Monitoring of mpounded Bluefin Tuna in St. Margaret's Bay. ( SCRS/77 /92). 3) Butler, M.J.A., and J.M. Mason, Jr.: Behaviour Studies on mpounded Bluefin Tuna (SCRS/77/93). 4) Hunt, J.J. (Editor): Proceedings of the Atlantic Bluefin Tuna Aging Workshop. Tir. Becket informed the Working Group that four of tagged bluefin recaptured in 977, and one of those recaptured in 976, were fish that had been released after capture by rod and reel. This supportsthe value of the technique even in the colder part of the bluefin range.

6 - 4 - Dr. Bagge submitted data on Danish and Swedish catches of 6 bluefin tuna made in the Kattegat (Table 5). French bluefin tuna catches from the Bay of Biscay were reported by Dr. Aloncle (Table 6). Mr. S.A. versen stated that except for one tuna caught 7 July (week 27) the Norwegian fishery started four weeks later in week 3. This is the usual time for starting the tuna seasonthere. 29 fishes, totalling kilos were landed during the weeks The main catch were landed in the two weeks 32 and catches were landed by 27 fishermen. The catches ranged between and 29 fishes. The bulk were caught on the coast of Hordaland and Sogn and Fjordane. Three fishes were reported from Rogaland, the neighbouring district south of Hordaland. The complete Norwegian catch is included in the Table 7.Only giant bluefin were caught.ndividual weights are lacking for 6 fishes in week 32. ndividual weights (gutted and without head) varied between 80 and 435 kilos, averaging kilos, corresponding approximately to kilos, mean 345 kilos live weight. No fishing stops or other restrictions were imposed. However, the fishery ended before September due to bad weather. No length measurements were recorded. Dr. Monteiro submitted the landing statistics of the Portuguese bluefin tuna catches made at Azores and Madeira slands (Table 8). Dr. Rodriguez-Roda informed the Working Group that in 977 three madragues were working in the south of Spain, 2 on the Atlantic coast at Barbate and Zahara de los Atunes and one on the Mediterranean coast at La Linea (Table 9). During the months of May, June and July the weather was not very satisfactory for the madrague fishery. Nevertheless it is evident that catches of bluefin tuna are steadily decreasing in this area ~total of 69 fish were measured)(table 0). Dr. Cort says that the period from July -August 977 was characterized by extremely bad weather which has cut down the activities of the Spanish tuna fleet in the Bay of Biscay. The improvement of weather during

7 - 5 - September made it possible that catches reached levels above the average. The catch per unit of effort was even the highest since 972: kg The age composition of catches is given in Table. The information on the bluefin tuna catches made by bait boats in the Canary slands given for the first time was made by Mr. Santos-Guerra (Tables 2-3). The US length composition data were reported by Mr. M.D. Lange of the Miami Laboratory of the National Marine Fisheries Service (Tables 4-9). The fish were measured as straight fork length in centimeters and tabulated within one week :intervals across tl e respective fishing seasons. Tables were submitted by Dr. J.C. Tyler (2). Results. ~rhe bluefin tuna catches of the Spanish madrague fishery which had recovered to 490 tons in 976 declined again to 339 tons in The catches of the Norwegian fishery increased instead from 69 fish in 976 to 2 9 giant tuna (= 587 tons), but were still smaller than in 974 and The French fishery in the Bay of Biscay recovered again to the le v el of 975 after a drastic drop of landings in 976 to on8 half due to the abnormally high water temperature until the second half of July 976. French catches increased from 268 tons in 976 to 487 tons in 977. The Spanish catches per unit of effort in this are2 were the highest since The Spanish bluefin tuna catches in the vraters of the Cenary slands amounted 250 tons and vere the largest since 97 4.

8 The overa.ll Canadian catches continued to increase and reached 972 tons, which was the largest catch since 97+. Also the US catcl.es amounting to 945 tons were slightly higher than in 976 and the second largest since The Norwegian Bluefin Tuna catches were of the knovm size composition (Fig. )., t tallied neither with the Canadian catch of giant tune., which were considerable larger as in 976, nor with the catches made in the Canary slands which consisted largely of smalle:t' fish. The Spanish madrague catch shows a recruit of some 2 year old fish, while the older component of the catch tallies with the length composition of the US catch of giant tuna (Fig. 2). As has to be expected the size composition of the US and Canadian purse seine catches tally widely. 7. The US and Canadian purse seine catches were dominated by 4 year olds. This year class dominated the catches already in 97 4, 975 and 976. The second largest group \'ras that of 2 year olds. 8. n the live bait fishery in the Bay of Biscay the strongest year class was again that of 2 year olds which was also the case in 975 and 976. This indicates strongly that the fluctuation pattern in the strenth of the recruit year classes did not tally in the eastern and western Atlantic during these years.

9 - 7 - References ( ) ALONCLE, H., HAMRE, J., RODRG\JEZ-RODA, J. and TEWS, K., 974: Fifth Repoit of the Bluefin Tuna Working Group. Observations on the size composition of Bluefin ~una catches from 970 to 972. Cons. int. l~plor. Mer, Coop. Research Report, No. 44, pp. -52 (2) ALONCLE, H., HAMRE, J., RODRGUE.0-RODA, J. and TEWS, K., 977: Sixth report of the Bluefin Tuna Working Group. Observations on the size composition of Bluefin Tu~a catches from 973 to 975. Cons. int.. E:cplor.. Mer, Coop. Research Report, No.. 7, pp (3) BARD, F.X., ORT,J.L., 976: Estimation des captures franco-espagnoles de thon rouge, Thunnus thynnus (L.) CCAT: SCRS/76/ES3 (4) BURNETT, C.D., BUTLER, M.J.. A.., DCYSON, C.A., 976: Canadian Taggir-g and Recapture Data of Large Pelagic Eish for the Period ( SCRS/76 /87) (5) BUTLER, M.J.A., CADDY, J.F.., DCKSO~~, C.A., HUNT, J.J., BURNETT, C.D., 976: Apparent Age anc. Growth, based on Otolith analysis, of Gic:.nt Blue fin Tuna ( Thunnus thynnus thynnus) in the Canadian Catch. (SCRS/76;87) (6) BUTLER, M.J.A., 976: The Trap (l'~ackerel) and mpoundment (Bluefin) Fishery in St. Margaret's Bay, Nova Scotia: ts Development. (SCRS/76/88) (7) CORT, J.L., FERNANDEZ P'ATO, C., and JARDENAS, E. de, 976: Observations sur la maturation sexuelle du thon rouge, ThuE~ thynnus (L.) du Golfe de Gascogne. Cons. int. Explor. Mer, C.M. 976: J (8) HAMRE, J., LOZANO, F., RODRGUEZ-RODA, J. and TEWS, K., 966: Second Report from the Bluefin Tuna Working Group. On the development of the Bluefin Tuna fisheries from 950 to 964 and further observations on size composition of Bluefin Tuna catches. Cons. int. Explor. Mer, Stat. News Letters, No. 25, pp. -34 (g) HM~RE, J., LOZANO, F., RODRGUEZ-RODA, J. and TEWS, K., 968: Third Report from the Bluefin Tuna Working Group. Observations on the size composition of Bluefin Tuna catches from Cons. int. Explor. Mer, Stat. News Letters, No. 38, pp. -27

10 - 8 - (0) HA}RE, J., MAURN, C., RODRGUEZ-RODA, J. and TEWS, K., 97: Report of the Bluefin Tuna Working Group. Observations on the size composition of Bluefin Tuna catches from Cons. int. Explor. Mer, Coop. Res., Ser. A, No. 23, pp. -49 () HMli~E, J., and TEWS, K., 964: (2) TYLER, J.C., Report from the Bluefin Tuna Working Group. On the size composition of Tuna catches from Cons. int. Explor. Mer, Stat. News Letters, No. 20, pp. -43 BAGLN, R.E., BERRY, F.H. and RVAS, L.R., 977: A review of the United States scientific research on the biology and the status of Bluefin Tuna stocks and of the Bluefin Tuna fisheries. CCAT Working Document SCRS/977, pp. -

11 Table. Canadian Catches of Blue fin Tuna from Atlantic Ocean, Landings (Nominal Catch in Metric Tons, Round \'Veight) -- Purse Rod & Year Traps** seine reel* Total *Note: Prior to 974 tagged and/or released fish are included in the rod and reel totals. * * >: o t e : From the catch in c u des a sm a proportion of incidental longline catches.

12 Table 2. Size composition (round Vveight per mille by 0 kg unit) of large... ~luefin r.r una captured in five localities along the Canadian Atlantic Coast in 976 Size P.E.. Nfld. N. B. Que. N S. class (kg) Rod and reel Rod and reel Rod and reel Rod and reel Trap Rod and reel Total n n n n n n n smooth. so /oo o f-j ( ctd)

13 Continuation table 2. Totals Mean weight (kg) Size class 80 kg = ' --' 9 577

14 - 2 - Table 3 Size composition of large 8luefin caught by rod and reel off Prince Edward sland during four consecutive months of the 977 season (.number of fish and round weight rer mille by 0 kg unit). Size July August September October class No. of No. of No. of No. of (kg) fish %o fish %o fish %" fish %o Totals l ~- ea n \'lt? i <J h t j_~gj ~ ~ 0--~ Size class 200 kg =

15 - 3 - Table 4. Size (fork length) composition of small Bluefin taken off the U.S. coast by Canadian purse-seine v~ssels in 977. Size Class (cm) No. of Fish smoothed loo 'rotal: Size category 40~ (fork length caiper)

16 - 4 - W?ig~t dis~r~hution of B~uefin ~~~~ l3n~ed in Denm:rk i.l"l The weight gr~y~lp refe~.:::; to gutted fisl:l,~:i th r;ilj s (kg) \ eight group kg ~---~ ~~~ ~ hh 350 3C: ':.., Total 6

17 - 5 - Table 6. French Bluefin Tuna catches in 977 from the Golfe de Gascogne (France) in kg Date Total weight Fish below 30 kg Fish above 30 kg

18 - 6 - Table Size composition (kg) of Norwegian Bluefin Tuna catches by smoothed weight frequency (%a) in 977. Group means Week No. w' w Total , ""'~ n \V' '-"'' N \V' ~ 265. q 268.

19 - 7 - Table 8. Portuguese Blue fin Tuna landings at Azores and Madeira slands in 977 in kg Month Azores sland Madeira slands Total January February March April May June July August September October Total Table g. Bluefin Tuna catch from three madragues in Southern Spain (Barbate, Zahara de los Atures and La Linea) in 977: Bar bate Number of fish kg Big bluefin tuna Little bluefin tuna g~ g~9 l_g ~ ~ ~-2~Q Zahara de los Atunes Bluefin tuna La Linea Bluefin tuna 0 0 Total

20 - 8 - Table 0. Size composition of Spanish madrague catches of Bluefin Tuna (Thunnus thynnus.) at Barbate in 977 3=== z======================~-=========~======= ======================B Length group cm. foo smoothed o ?0? ? ? o ?.? ? N

21 - 9 - Table. Demographic structure of Spanish Bluefin catch and total number of fish caught in the Bay of Biscay Age group Number of fish V 5 37 V 346 V 29 V 94 Total Table 2. Spanish catches of Bluefin Tuna in the Canary slands, Year Catch in metric tons and round weight

22 Table 3. Size composition of Bluefin Tuna caught by baitboats in the Canary slands during the 977 season. 8j~ze c;j a:-3s C: e) 00 c /eo S"0othe:.i e (' 20? hO 250 ~60? ? Lt('l '+00 8??L, ;n p.r; 92 R"'2: _ h()../ () l~ Nn~be~ cf fish ~ 2 t: ono

23 \) f--l Table 4. Sample length frequency by week of giant Atlantic Bluefin Tuna caught by rod and reel in the Bahamas in 977(sampe = 5 fish).. Length 5/5-5/22-5/29-6/5- t+ Week 0 /oo cm 5/2 5/28 6/4 6/ smoothed E

24 .. i. ; : Table 5. Samhle len~th-frequency by week of small Atlantic Bluefin una caught by sport fis ing of the U.S. Mld-Atlantic coast in 977. Total catch 56 MT, total samples 96 fish i Week. '... 0 s \...0 \...0 \...0 \...0 c- c- c- c- c- CfJ CfJ CfJ CfJ 0\ 0\ 0\ 0\ rl ~ ~ CfJ Lr\ C\J 0\ \...0 t<"\ 0 \...0 t<"\ 0 c- t<"\ 0 c-.._j- 0. ~ ~ C\J ~ C\J t<"\ ~ C\l C\J ~ ~ C\J cd s +' w. OD +' $:::! Q) Lr\ \...0 \...0 \...0 \...0 c- c- c- c- c- CfJ CfJ CfJ CfJ 0\ 0\ 0\ 0 0 H ~ ()\ Lr\ C\J ()\ \...0 t<"\ 0 c-.._j- ~ c- """"" ~ ~ CfJ ~ ~ CfJ 8 0 C\J ~ ~ C\J ~ ~ C\J t<"\ ~ C\J C\J ~ ~ l 0 54 r i! i ; ~ : l !4 ' 6 32 ) ! ' 9 i 74 6 i ; 80 5 i! ( c td.) \) \)

25 Continued table 2_ Week - \.0 \.0 '"d \.0. \.0. :'-. :'- :'- :'- :'- CO (j)... CO CO CO 0\ 0\ 0\ El \ ~ -r- CO.....! L!\ -0 C\l -r- 0\ -r- \.0 t<\ 0 \.0 t<\ 0 :'- -P C\l -r- C\l t<\ t<\ 0 :'- -=:;:f- -r- C\l C\l 0 -r- -r- C\l ~.! El -P QD L!\ \.0 \.0 UJ. \.0 ~.. \.0. :'-. :'- :'- :'- :'- CO CO rl CO. CO 0\. 0\. 0\. m P 0 Q) 0\ L!\ C\l 0\ \.0 t<\ 0 :'- -=:;:f- -r- :'- -=:;:f- -r- CO -=:;:f- -r- CO 0 ~ H C\l -r- -r- (\) -r- -r- C\l t<\ ~ C\l C\l -r- --- E-l ~ go l l 3! 2 02 ; 5 4 [\) i N! 04 r! f 06 j 2 3 4! l 0 f 5 23! ' f j 2 l 2 3 i l : i j i 4! j 5 t ' t! 6 ' 0 3 l : 8 i ' i 8 ' t 2 20 ' 4 3 < 22 8! j ' f t 24 0 l 5 i ~ ~ 26 ' 3 3 rf [ : '! f 28! t 4 5 t ; j 30 l l 2 5 j ; ' l! i.; t i! 34 t 2 9 i l i 36 8! l 38! ' 2 6! i! i 3 j ~ j!50 i f! 52! 0 t!! l 54 3! t l f l 0 \ t (ctd) r ' l!! -

26 m 8t[+oorns ooj 0 "L" Z - L L~. L. 9 ~ - L o~ "L 6 -"L" "L"6-9 9z 9 ~z -"9"6~ ~ -"9"6~ GJ rl p -P re) g G) r- -P 0 >=! U ~ 9 t - ~ 6z tt+:su8'j 0..--t<\ t<\..-O »~--- r~ o..-ooo..-oo m m m "9"~~-..- {'<\. r ---- ~ - -t-~~ ~ - ---l ~ '<\ \ r-- '<\.., ~ t ~ m ' -- ' \..0 ~ N ~ ,---- l\..0 ' t ~ ~ t----- ro ~ l'r' ---r t-..- -r l.-. - \..OCJOC\J"<j-\..OCDO ~ m m \..0 \..0 \..0 \..0 \..0 c-- U2 or-.,.-.,.-.,.-.,.-.,.-.,

27 Table 6. Sample length-fre~uency by week of giant Atlantic Bluefin Tuna caught by hand-gear off the NE coast of the US in 977 (total catch 634 MT, total sample= 062 fish). Week E J' oo 6/26:.. 7/3-7/0-7/7-7/24-7/3-8/7-8/4-8/2-8/20-9/4- smoothed 7/2 7/9 7/6 7/23 7/30 8/6 8/3 8/20 8/27 9/3 9/ '\) Vl ~ ~ l~ Length 6/9- cm 6/ ' :

28 Table 7. Gample length-frequency by week of small Atlantic Length cm T. luefin ~.'una caught by U. S. purse-seine fleet in 977 (total catch = 972r T, total sampled 682 fish) ---r _; , Total ~ /oo ' 23 ' : o ~ smoothed 74 --~---l j ~ ~ ~ j 2 s; : 7 7! : 5! 6 8? n n n

29 Table s. Sample length-frequency by week of small Atlantic Blue fin Tuna caught and or tagged by U.S. purse-seine fleet in 977 (total catch 86MT, total sampled= 2388 fish) Week 'Length 26.6.! {! Total 0 /oo cm ! smoothed t 90 0 l 92 0 i ~ l Sx ~

30 Table 2 Sample length-frequency by week of giant Atlantic bluefin Tuna caught by U. S. purse-seine fleet in 977(total catch= 68MT~ total sampled = 388 fish). Week Length 8/28-9/4-9/- 9/8- o; cm 9/3 9/0 9/7 9/24 :4 00 smoothed l \) l:304 a o CD

31 [\) '-.0 Table 20. US-Bluefin Tuna catches Purse Seine, Hand Gear for Sport Fishing Totals Year Giant and School Tuna Giant Tuna for School Tuna (MT) * * * ncludes estimated October catches of small (6MT) and medium (23MT) purse seine tuna in special scientific quotes

32 Table 2. Dates, catches and approximate age composition of 976 US Bluefin Tuna Fisheries Fishery Dates Catch by Catch by Approximate Small fish, open close number of fish round weight (MT) age composition by number purse seine ~ 2 % age 2 Re-gular Season 0 June 29 June MT 88 % age 3 Tagging Season 8 July 8 July f32 % age 224 MT 47 % age 2 2 % age 3 [47%age Small fish, 34 % age 2 sport Jan. 3 Dec MT 6 % age 3 Large fish, 3 % ages 4-5 purse seine Sept. 2 Sept MT age N Large fish, hand gear 8 May 6 Sept ~Q._~~-- age MT 0

33 \>J f-- Table 22. Dates, catches and approximate age composition of the 977 U.S. Bluefin Tuna Fisheries Fishery Small fish, purse seine open Regular season 5 June Tagging Season July Small fish, sport Large fish, purse seine Large fish, hand gear Northern Area Southern Area Medium fish, :r:urse seine lspecial quota) * Estimated? Oct. Jan. 3 Sept. Jan. Jan. 6 Sept.? Oct. Dates close 20 june 5 July? Oct. 24 Sept. ) 8 Sept. 5 Sept. 9 Sept. still open? Oct. Catch by number of fish * * ) Last data included for catch in this table; season closes 3 Dec. Catch by round weight (MT) 972 MT 86 MT 6 MT* 56 MT 68 MT 634 MT 23 MT* 945 MT Approximate age composition by number ~ 25 % age 2 70 % age 4 5% ages,3,5 t 7 % age 9 % age 2 2 % ages 3-4 l-5 % age 69 % age 2 2 % age 3 4 % ages 4-5 age 7-9+ age age 5-8

34 50 USA Canada Norway Canary s la ,927 --l-288 ' ' 7 9 7, : "'.../. "'.....-"'"',... " ' ~ J '..... _ ,;, ", " " ~-, , Figure ~ Weight composition of Bluefin TUna catches made in USA, : Canada, Norway and Canary sland (Spain) kg