REPORT OF OBSERVER PROGRAM FOR JAPANESE TUNA LONGLINE FISHERY IN THE ATLANTIC OCEAN FROM AUGUST 2004 TO JANUARY 2005

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1 SCRS/5/95 Col. Vol. Sci. Pap. ICCAT, 59(): 3- () REPORT OF OBSERVER PROGRAM FOR JAPANESE TUNA LONGLINE FISHERY IN THE ATLANTIC OCEAN FROM AUGUST TO JANUARY 5 T. Matsumoto SUMMARY This paper summarizes longline observer program conducted by Japan from August to January 5. Nine cruises or 35 days of fishing were monitored in the tropical and temperate areas of the Atlantic. Data collected through this observer program are ) information on fishing boat, fishing gear and fishing processes, ) oceanographic and weather information, and 3) biological information such as species identification, size and maturity on tunas as well as other catches. A total of 3 species, including four tuna and two billfish species including swordfish, which consisted of 355 individuals, were recorded., bigeye or bluefin tuna was the most frequently among commercially important species. From the length frequencies of the catch, several tuna species showed clear modes and, for several species, the mode and range of length differed depending on areas. Many of adult females of bigeye tuna in the tropical area were considered to be mature judging from gonad weight. Catch data by branch line number showed that bluefin tuna was mainly by the branch lines of intermediate or shallowest depth. Biological samples were also collected for such as gonad, stomach content and muscle. Pop-up tagging for bigeye tuna was also conducted. RÉSUMÉ Le présent document récapitule le programme d observateurs palangriers réalisé par le Japon d août à janvier 5. Neuf campagnes ou 35 jours de pêche ont fait l objet d un suivi dans les eaux tropicales et tempérées de l Atlantique. Les données recueillies par ce programme d observateurs sont ) des informations sur les navires de pêche, les engins de pêche et les processus de pêche ; ) des informations océanographiques et climatologiques ; et 3) des informations biologiques telles que l identification des espèces, la taille et la maturité des thons ainsi que d autres captures. Au total, 3 espèces, dont quatre espèces de thonidés et deux d istiophoridés, dont l espadon, qui représentaient 3.55 spécimens, ont été consignées. Le germon, le thon obèse et le thon rouge étaient les espèces les plus fréquemment capturées parmi les espèces commercialement importantes. A partir des fréquences de taille de la capture, plusieurs espèces de thonidés ont manifesté des modes clairs et, pour plusieurs espèces, le mode et la gamme de longueur ont différé en fonction des zones. De nombreuses femelles adultes de thon obèse dans la zone tropicale ont été considérées matures à en juger par le poids gonadique. Les données de capture par nombre d avançons ont indiqué que le thon rouge était principalement capturé par les avançons de profondeur intermédiaire ou faible. Des échantillons biologiques (gonades, contenu stomacal et muscle) ont également été prélevés. On a également réalisé le marquage du thon obèse au moyen de marques pop-up. RESUMEN En este documento se resume el programa de observadores que llevó a cabo Japón desde agosto de hasta enero de 5. Se realizó un seguimiento de nueve cruceros o 35 días de pesca en las zonas tropicales y templadas del Atlántico. Los datos recopilados en este programa de observadores son: ) información sobre buques de pesca, artes de pesca y procesos de pesca; ) información meteorológica y oceánica, y 3) información biológica como identificación de especies, talla y madurez de los túnidos y de otras capturas. Se registraron un total de 3 especies, entre las que se incluían cuatro túnidos, dos marlines y pez espada, y 3.55 ejemplares. Las especies comerciales importantes más frecuentemente National Research Institute of Far Seas Fisheries, Fisheries Research Agency, 5-7- Shimizu-Orido, Shizuoka-Shi, Shizuoka, -33, Japan. 3

2 capturadas fueron atún blanco, patudo y atún rojo. Las frecuencias de tallas de las capturas de varias especies de túnidos mostraban claras modas y, para varias especies, la moda y el rango de talla diferían en función de la zona. Muchas de las hembras adultas de patudo en la zona tropical se consideraron adultas a juzgar por su peso gonadal. Los datos de captura por número de brazolada mostraban que el atún rojo se capturaba sobre todo en las brazoladas de profundidades más superficiales o intermedias. Además, se recogieron muestras biológicas como gónadas, contenidos estomacales y músculos. También se llevó a cabo un marcado pop-up de patudo. KEYWORDS Long lining, Bigeye tuna, Bluefin tuna, Bycatch, Size composition, Sexual maturity, Tagging Introduction In recent years the resources of tunas, not only temperate tunas (bluefin and southern bluefin) but also tropical tunas (bigeye and yellowfin), appear to be exploited more heavily than before, and most stocks seem to be almost at MSY level or overfished. Under these situations, Japan reduced its distant water tuna longline fleet by about % in 999 in order to reduce fishing pressure on tunas. Management measures have been introduced to most of the stocks the ICCAT is managing, not only for tuna species but also for other species. For example, regulatory measures for swordfish, Atlantic blue marlin and white marlin are also introduced in the Atlantic. As a result, further researches on the stock status as well as the fisheries themselves are required in order to provide better materials for decision-making. For example, records in the logbooks are commonly used for the source of stock assessments, but it is not known precisely how those figures in the logbook come up through the fishing processes. Therefore, Fisheries Agency of Japan has begun Atlantic tuna longline vessel observer program since late 995 which includes biological surveys on tunas and other commercial species as well as bycatch species, taking records of all fishing processes and taking samples for bio-chemical works, aging, etc. Also, this program is being conducted in response to the recommendation of ICCAT made on bigeye and yellowfin tunas in 99, and the number of vessels monitored is increasing in recent years in response to the recommendation concerning swordfish catches by the tuna longline fishery (-3). Two to nine cruises have been monitored annually since then. The results of the past cruises (from 997 to January ) have been reported to SCRS meetings (Matsumoto and Miyabe, 997, 99, 999,, ; Matsumoto et. al.,, 3, ). Fisheries Agency of Japan is also conducting observer program for the vessels targeting southern bluefin tuna (Itoh and Miyauchi, ), but this paper reports only observer program for the vessels operating in the Atlantic Ocean. This paper presents summary results of the observer program conducted by Japan from August to January 5 (nine cruises) in the Atlantic. Observers and trips Nine trips (a total of 35 operations) were made between August and January 5. Summary of the trips is given in Table. The area of operations is shown in Figure. Eight vessels (a total of 35 operations) monitored from August to December operated in the north Atlantic (mainly around off Iceland and partly around off Grand Bank or in the central north Atlantic) and one vessel (7 operations) monitored from December to January 5 operated in the tropical area of central (south) Atlantic (around off Abidjan). The observers employed by the Fisheries Agency of Japan were ex-crews of longliner, and trained by the staffs of the National Research Institute of Far Seas Fisheries (NRIFSF) and other organizations. After the trips were made, the meeting for de-briefing from the observers was held to help assure the results and data they collected. 3 Methods Information collected through this observer program was categorized into three; ) information on fishing boat, fishing gear and fishing process including branch line number of catch, ) oceanographic and weather information, and 3) biological information on all catches. The last item includes identification and composition of species, life status of the catch (alive or dead), length/ body weight, maturity of the catch and biological sampling

3 (gonad, otolith, and so on). Pop-up tagging for bigeye tuna in the tropical area was also conducted. Given below is the summary of information collected. 3. Information of the vessel characteristics and fishing gears Items of vessel characteristics and fishing gears acquired are tabulated in Table. They were mainly obtained by the interview to the skippers and captains. 3. Identification of species and related information In principle, all the catch were identified and recorded, and the catch which failed to be hauled on the deck was recorded as well only when the species was identified. The observer coverage on an operation basis (in terms of number of hooks observed) was between 9 and % (7% on average). Data were directly collected by the observers, although some data were obtained with the help of crew members. Each catch was identified whether they were alive or dead immediately when brought up on board or released at the deck side, and alive was further separated into vigorous and weak. In order to study difference of catch by depth, branch line number was recorded for each catch when possible. 3.3 Measurements of the fish Length by cm interval (round up) and clasper length of sharks by.cm interval, body weight (in principle to the nearest kg, and partly to the nearest.kg), gonad weight (for tunas and billfishes, mainly for female, to the nearest 5 to g) and product weight (to the nearest kg) were measured as many as possible. When there was substantial numbers of catch, priority was given to tunas and billfishes, but in principle the number of individuals was counted for all catch. Different length measurements were taken: fork length for tunas (for some individuals pre-dorsal length was also measured), eye-fork length for billfishes, precaudal or fork length for sharks, disk length for rays, and total or fork length for other fish. Lengths were measured with a caliper, a scale or a tape measure. 3. Maturity Maturity of tunas was judged by GSI where GSI = gonad weight(g)/(length(cm)) 3. Also the status of maturity of ovaries was identified by observing their cross section by eyes on board on the basis of the definition (M to M) shown below. As for sharks, maturity was checked by the existence of sperm and embryos for males and females, respectively. Definition of the status of maturity for the ovaries of tunas and billfishes: M : Ovary is small and no grains of egg are visible. M : Ovary is larger than M and small grains of egg are visible. Arteries are developed on the surface of ovary. M3 : Each grain of egg is over. to.5mm and ovary is full of them. The color of egg is light pink and no translucent egg is observed. Arteries are well developed. M : Ovary is very large and some translucent eggs are observed which are easy to come off. M5 : Many eggs are exfoliated in the ovary and are about to get out of. M : Ovary is comparatively large but it has a open cavity inside. 3.5 Biological sampling The following samples were taken.. Gonad for maturity study: bigeye and bluefin tunas. Stomach content for food habit: bluefin tuna 3. Muscle for genetic study: bigeye and bluefin tunas 3. Pop-up tagging for bigeye tuna Pop-up tagging was conducted for bigeye tuna in the tropical area (off Abidjan) to investigate vertical and horizontal swimming behavior. A pop-up tag (Microwave Telemetry, PTT-) was harpooned aiming at the side 5

4 body under the dorsal fin while the fish was kept at the sea surface and then released by cutting the line. Length and weight of the fish released were estimated by the observer s or crew s eyes. The tags for tunas recorded depth and water temperature every one hour and were programmed to pop-off after a certain period of time (,, or months). When the tag floats up, it transmits the data to satellite and position after floating up can be monitored by the satellite. Results. Catch by species The list of species and the number of catch by area are shown in Table 3 and catch composition by area is shown in Figure. A total of 3 species (including 9 unidentified species), 355 individuals were recorded. Also the numbers and weight of catch, and the number of fish measured and sampled in the north and south Atlantic are shown in Table. Overall CPUEs for albacore, yellowfin, bigeye, bluefin tuna, swordfish, total billfishes, total sharks and other fish by fishing area are shown in Table 5, along with the number of operations in each area. Details of catch information for each area are as follows. Off Iceland A total of 7 species (including unidentified species), 3 individuals were recorded. Blue shark was dominant (55%, 99 individuals), and bluefin tuna (9%, 5 individuals) followed. and swordfish were also. Off Grand Bank A total of 5 species (including 3 unidentified species), 3 individuals were recorded. Bigeye tuna was dominant (33%, 7 individuals), and blue shark (9%, 9 individuals) followed. Swordfish (3%, individuals), bluefin tuna (%, 3 individuals), yellowfin tuna were also. Central north Atlantic A total of species (including unidentified species), 9 individuals were recorded. and blue shark was dominant (3%, 3 individuals). Bluefin tuna (%, individuals) and swordfish were also. Off Abidjan A total of species (including unidentified species), 3 individuals were recorded. Bigeye tuna was dominant (3%, 5 individuals), and longnose lancetfish (3%, 5 individuals) followed. These two species accounted for % of the total catch. The proportion of sharks was small (%, individuals). Longbill spearfish was also.. Life status of fish The percentages of the fish alive by species are shown in Table. Survival rate of bluefin tuna was %. Bigeye tuna in the north Atlantic showed higher percentage of survival than that in the tropical areas (% in the temperate area and 5 % in the tropical areas). Survival rate of sharks differed depending on areas and species but usually showed comparatively higher percentage of survival..3 Length of the fish Length frequencies of major tuna and billfish species are shown in Figure 3. Bluefin tuna showed clear modes around 7cm and cm FL. in the north Atlantic showed modes around 9 and cm FL. As for bigeye tuna, most fish measured was between 9 and 3cm FL in the north Atlantic. On the other hand, bigeye tuna off Abidjan mostly ranged form to cm. Swordfish in the north Atlantic was mostly between 3 and cm EFL.. Types of products Types of products, which were processed on board of longline boats observed, are given in Table 7. were mainly processed by removing fins and tail only and partly into fillet or dress. Other tunas were processed into gilled and gutted. Swordfish was processed into fillet or dress depending on fish size (processed into fillet for the fish approximately more than cm EFL or 3kg whole body weight). Longbill spearfish was processed into dress. As for sharks, not only fins but also carcass (processed into fillet or dress) was held for several spe-

5 cies, which are unloaded at foreign ports..5 Maturity The relationships between fork length and gonad weight of female tunas (bluefin and bigeye tunas) are shown in Figure. Compared with the curve of GSI=3. which is often used to roughly define matured fish (where GSI=gonad weight(g)/(fork length(cm)) 3 ), all bulefin tuna individuals and bigeye tuna in the north Atlantic were under that line, suggesting that the fish were sexually inactive, but most bigeye tuna off Abidjan were mature, although sample size was small. The status of maturity of female tunas is shown in Table. If after M3 (eggs grow large) is regarded as matured, as for bluefin tuna, some individuals were supposed to be mature. However, as the gonad weight was very low (Figure ), there is possibility of misreading by the observers. As for bigeye tuna, all the individuals off Abidjan were mature.. Catch by branch line number The number of catch by branch line number is shown in Figure 5 for several tuna and billfish species. As for bluefin tuna, though the trend differed depending on vessels, many fish were by shallowest or intermediate branch lines. in the north Atlantic were also mainly by shallowest or intermediate branch lines, although in a part of cruise mainly by deep branch lines. Bigeye tuna in the north Atlantic was by branch lines of each depth comparatively equally. The trend of swordfish was not clear because of insufficient number of observation. This kind of data is informative and very useful not only for fishing but also for standardizing CPUE in stock assessment..7 Biological sampling The number of samples taken is shown in Table. A total of 57 gonads, stomach content and 9 muscle were collected.. Pop-up tagging of bigeye tuna Information of the fish which pop-up tag was attached to is shown in Table 9. A total of 5 fishes were tagged and released. So far, pop off of two tags were confirmed. Analyses of tag data have not yet been done. 5 Future outlook of Observer Program This program will be continued. Nine vessels or about 5 days of fishing will be monitored in the north or south Atlantic between August 5 and approximately January, some of which are now ongoing. As the area and season are limited and most cruises are conducted in the north temperate Atlantic, it is desired to increase the coverage for the tropical areas. Acknowledgements We are thankful to the crew of the longline vessels, who allowed us to do this program. Also, special thanks should be given to Messrs Yoshiteru Oyabu, Shin ichi Kadota, Ichimatsu Yamasaki, Yukatsu Hama, Nagao Okamoto, Takashi Aoyama, Shinya Araki, Kazuo Sugiyama and Masaharu Onita, who boarded as a scientific observer, to the staffs of JAMARC (Marine Fisheries Research and Development Department of Fisheries Research Agency), who coordinated observer employment, training and de-briefing meeting, to the staffs of Japan Fisheries Resource Conservation Association, who coordinated observer trip and preparation of observer gears, and to the stuffs of the Japan Tuna Fishermen s Cooperative Association and its Las Palmas and Cape Town offices for their kind assistance. Reference ITOH, T. and M. Miyauchi.. Report of Japanese scientific observer activities for southern bluefin tuna fishery in 3. CCSBT-ESC/9/3; pp. 7

6 MATSUMOTO, T. and N. Miyabe. 99. Report of 997 observer program for Japanese tuna longline fishery in the Atlantic Ocean. Col. Vol. Sci. Pap. ICCAT, (3): 3-7. MATSUMOTO, T. and N. Miyabe Report of 99 observer program for Japanese tuna longline fishery in the Atlantic Ocean. Col. Vol. Sci. Pap. ICCAT, 9(): -. MATSUMOTO, T. and N. Miyabe.. Report of 999 observer program for Japanese tuna longline fishery in the Atlantic Ocean. Col. Vol. Sci. Pap. ICCAT, 5(): MATSUMOTO, T. and N. Miyabe.. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean in (until July). Col. Vol. Sci. Pap. ICCAT, 5(5): 9-9. MATSUMOTO, T. and N. Miyabe.. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean from August to July. Col. Vol. Sci. Pap. ICCAT, 5(5): 7-7. MATSUMOTO, T., H. Saito and N. Miyabe. 3. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean from September to March. Col. Vol. Sci. Pap. ICCAT, 5(5): MATSUMOTO, T., H. Saito and N. Miyabe.. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean from September to January 3. Col. Vol. Sci. Pap. ICCAT, 5(): 5-. MATSUMOTO, T., H. Saito and N. Miyabe. 5. Report of observer program for Japanese tuna longline fishery in the Atlantic Ocean from August 3 to January. Col. Vol. Sci. Pap. ICCAT, 5(5): 9-7.

7 Table. Summary of observer trips. Cruise ID AT AT AT3 AT AT5 AT AT7 AT AT9 Departure //3 //3 /9/3 /9/5 /9/ /9/7 //3 // //5 Las Palmas (Spain) Reykjavík (Iceland) Reykjavík (Iceland) Las Palmas (Spain) Cork (Ireland) Las Palmas (Spain) Barboa (Panama) Cork (Ireland) Observer boarded on the ocean Start of operation //3 //7 /9/7 /9/ /9/ // // //3 // Area operated Off Iceland Off Iceland Off Iceland Off Iceland, Central North Atlantic and off Grand Off Iceland and off Grand Bank Off Iceland Off Iceland Off Iceland Off Abidjan -59ºN, 5-5ºW 9-ºN, -ºW 5-59ºN, -7ºW 39-5ºN, 3-5ºW -5ºN, 5-ºW 5-53ºN, -39ºW -53ºN, -ºW -5ºN, -3ºW -9ºS,ºW-ºE Number of operations moni End of operation // // // //5 //5 // // // 5// Arriving at port // // // //7 // //9 // //5 5// Cork (Ireland) Observer dis-embarked on the ocean Cork (Ireland) Halifax (Canada) Cork (Ireland) Lisbon (Portugal) Torshavn (Faroe Islands, Denmark) Las Palmas (Spain) Cape Town (Republic of South Africa) Table. Items of the vessel characteristics and fishing gears recorded. Item Length overall (m) Engine power (kw) Maximum amount of fuel (ton) Gross tonnage (domestic) Year of construction Capacity of well (ton) Number of crew Number and nationality of foreign crew Length of main line (km) Item Length of branch line and float line(m) Material of main line, branch line and float line tori-pole (Bird bycatch mitigation measure) (present or absent) Bait casting machine (present or absent) Number of baskets per set Number of hooks per basket Number of total hooks per set Maximum and minimum hook depth (m) (estimation by the crew) The kind of baits 9

8 Table 3. The number of catch by species and by area. Scientific name English name Off Iceland Off Grand Central north Atlan- Off Abidjan Thunnus alalunga 7 3 Thunnus albacares Yellowfin tuna Thunnus obesus Bigeye tuna 7 5 Thunnus thynnus Bluefin tuna 5 3 Tetrapturus pfluegeri Longbill spearfish Xiphias gladius Swordfish 7 Unidentified fishes Alepisaurus spp. Lancetfishes Alepisaurus ferox Longnose lancetfish 5 Alepisaurus brevirostris Shortnose lancetfish 5 3 Gadidae Unidentified codfish Lophiiformes Unidentified anglerfish 35 Lampris guttatus Opah 3 Trachipteridae Ribbonfishes Trachipterus trachipterus Deal fish Bramidae Pomfrets 3 Taractichthys longipinnis Bigscale pomfret Taractes asper Rough pomfret Coryphaena equisetis Pompano dolphin Serranidae Sea basses Gempylus serpens Snake mackerel Lepidocybium flavobrunneum Escoler 37 Ruvettus pretiosus Oilfish Masturus lanceolatus Sharptail sunfish Mola mola Ocean sunfish 5 Scomberesocidae Unidentified saury Pseudocarcharias kamoharai Crocodile shark 5 Alopias superciliosus Bigeye thresher Alopias vulpinus Thresher shark Isurus oxyrinchus Shortfin mako Lamna nasus Porbeagle 7 Carcharhinus longimanus Oceanic whitetip shark 7 Galeocerdo cuvieri Tiger shark Prionace glauca Blue shark Rajiformes Unidentified ray Dasyatis violacea Sting ray 5 Total

9 Table. sampled. North Atlantic Number recorded Length Product Weight (kg) Weight Number or weight of fish sampled Live whole weight (kg) Number Number Weight Sex Alive or not Gonad weight Maturity Clasper length Whole body Biological sampling Yellowfin tuna 3 Bigeye tuna Bluefin tuna Swordfish Bigeye thresher Thresher shark 3 Shortfin mako 3 3 Porbeagle Oceanic whitetip shark Tiger shark Blue shark Unidentified ray Sting ray Branch line number Otolith Stomach Muscle content Gonad Others* Total *: Other teleostei than tunas and billfishes. Unidentified lancetfish (n=7) and so on. 7

10 Table. sampled. (continued) South Atlantic (off Abidjan) Number recorded Length Number or weight of fish sampled Live whole weight (kg) Product Weight (kg) Number Weight Number Weight Sex Alive or not Gonad weight Maturity Clasper length Whole body Biological sampling Bigeye tuna Longbill spearfish 9 Crocodile shark Shortfin mako Blue shark Stomach content Branch line number Otolith Muscle Gonad Others* Total *: Other teleostei than tunas and billfishes. Longnose lancetfish (n=5) and so on. Table 5. CPUEs for major species by area. CPUE = number of fish / number of hooks. Area Number of Yellowfin Bigeye Bluefin Total billfishes sharks Others Total Total operations tuna tuna tuna Swordfish Off Iceland Off Grand Bank Central North Atlantic Off Abidjan

11 Table. Percentage of the fish alive. Species Total Alive Dead Ambiguous or unknown Percentage alive Vigorous Weak No details North Atlantic Yellowfin tuna 3. Bigeye tuna Bluefin tuna Swordfish Bigeye thresher. Thresher shark 5. Shortfin mako Porbeagle Oceanic whitetip shark Tiger shark. Blue shark Unidentified ray. Sting ray 5. Off Abidjan Bigeye tuna Longbill spearfish. Crocodile shark 5. Shortfin mako. Blue shark

12 Table 7. The types of product by species. Species Yellowfin tuna Bigeye tuna Bluefin tuna Longbill spearfish Swordfish Shortfin mako Porbeagle Oceanic whitetip shark Blue shark Type of products FT or F or D G G G D F or D F or D and fins D and fins D and fins D and fins Note: F = Fillet, D = Dress, G = Gills, internal organs, fins and tail were removed, FT = Fins and tail were removed. Table. Maturity of female tunas judged from ovary. For legend, see text. Species Area Total M M M3 M M5 M Bluefin tuna North Atlantic North Atlantic Bigeye tuna North Atlantic 7 Bigeye tuna Off Abidjan 9 3 7

13 Table 9. Information on pop-up tagging. Programmed pop off period (months after released) Pop off Release Cruise ID Tag Serial ID Argos ID Scheduled pop off date Success/ failure Date Lat. Lon. Date (GMT) Time (GMT) Lat. Lon. AT9 77 5//3 Failure Bigeye tuna //3 5: 9 S E 75 9 AT /7/ Success 5// (not yet analyzed) Bigeye tuna //3 7:5 59 S 5 E 7 5 AT //3 Failure Bigeye tuna //3 :5 9 S E 35 AT /7/ Success 5//7 (not yet analyzed) Bigeye tuna //3 9:5 9 7 S E 35 AT //3 Failure Bigeye tuna //3 : 9 S E 75 * Gilled and gutted. Species Estimated fork length (cm) Estimated product weight (kg) * 75

14 Off Iceland Off Grand Bank At- Central north lantic Off Abidjan Figure. Positions of operation in the Atlantic. % % % % % % Off Iceland Off Grand Bank Central North Atlantic Off Abidjan Yellowfin tuna Bigeye tuna Bluefin tuna Swordfish Total billfishes Total sharks Others Figure. Species compositions of the catch in each area. 7

15 7 5 3 n=5 Bluefin t una Nort h Alt ant ic Bigeye tuna Nort h Alt nat ic Fork length (cm) n= Fork length (cm) n= Nort h Alt nat ic Bigeye tuna Off Abidjan n= Fork length (cm) Fork length (cm) n=7 Swordfish Nort h Alt nat ic Eye fork length(cm) Longbill spearfish Off Abidjan n= Eye fork length(cm) Figure 3. Length frequencies of tunas and billfishes. 77

16 Gonad weight(g) 5 3 Bluefin tuna North Altantic n= 5 GSI= Fork length(cm) Gonad weight(g) Bigeye tuna North Atlantic n= GSI=3 5 5 Fork length(cm) Gonad weight(g) Bigeye t una Off Abidjan n= 7 GSI=3 5 5 Fork length(cm) Figure. The relationship between fork length and gonad weight of female tunas. The curve in the graphs denotes the line GSI=3. where GSI=gonad weight(g)/(fork length(cm)) 3. 7

17 Bluefin tuna North Atlantic (cruise ID AT) Bluefin t una Nort h At lant ic (cruise ID AT) n= n= Bluefin tuna North Atlantic (cruise ID AT3) Bluefin tuna North Atlantic (cruise ID AT) n= n= Bluefin t una Nort h At lant ic (cruise ID AT5) Bluefin t una Nort h At lant ic (cruise ID AT5) n= n= Bluefin t una Nort h At lant ic (cruise ID AT) Bluefin t una Nort h At lant ic (cruise ID AT7) n= n= Bluefin tuna North Atlantic (cruise ID AT) 5 5 n= Figure 5. Number of catch of several tunas and billfishes by branch lines. 79

18 North Atlantic (cruise ID AT) North Atlantic (cruise ID AT) n= n= North Atlantic (cruise ID AT3) n=9 North Atlantic (cruise ID AT) n= North Atlantic (cruise ID AT) North Atlantic (cruise ID AT5) 5 5 n= n= North Atlantic (cruise ID AT5) North Atlantic (cruise ID AT) 3 n= n= North Atlantic (cruise ID AT7) 3 n= Figure 5. Number of catch of several tunas and billfishes by branch lines. (continued).

19 Yellowfin tuna North Atlantic (cruise ID AT) Bigeye tuna North Atlantic (cruise ID AT) n= n=5 3 Swordf ish North Atlantic (cruise ID AT) n= Swordfish North Atlantic (cruise ID AT) n= Swordf ish North Atlantic (cruise ID AT) Swordfish North Atlantic (cruise ID AT) n=3 3 n= Swordf ish North Atlantic (cruise ID AT5) Swordf ish North Atlantic (cruise ID AT5) n= n= Figure 5. Number of catch of several tunas and billfishes by branch lines. (continued).