National Tuna Fisheries Report of Japan as of Miyabe, N., M. Ogura, T. Matsumoto and Y. Nishikawa

Transcription

1 SCTB17 Working Paper NFR 11 National Tuna Fisheries Report of Japan as of 2004 Miyabe, N., M. Ogura, T. Matsumoto and Y. Nishikawa Fisheries Research Agency National Research Institute of Far Seas Fisheries (NRIFSF) 5 Chome 7-1, Orido, Shimizu, Shizuoka , Japan July 2004

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3 National Tuna Fisheries Report of Japan as of 2004 Miyabe, N., M. Ogura, T. Matsumoto and Y. Nishikawa Fisheries Research Agency National Research Institute of Far Seas Fisheries (NRIFSF) 5 Chome 7-1, Orido, Shimizu, Shizuoka , Japan 1. Introduction This paper describes recent trends in the Japanese tuna fishing activities (longline, pole-and-line and purse seine) mostly in the central and western Pacific Ocean (WCPO, west of 150W). Brief fishing report for each fishery is given for 2003, and fleet, fishing effort and catch statistics are also included. Purse seine catch statistics are updated to 2003 but it is not possible to provide them for longline and pole-and-line fisheries as the current level of logbook compilation is not yet enough to make the estimation for that year. Catch statistics of boat smaller than 20 gross tonnages (GRT) for longline and pole-and-line, which is not covered by the current logbook system (pole-and-line, troll, etc) or insufficient to do so (longline), are not compiled by the NRIFSF but referred to the publication of the Statistical Division of the Ministry of Agriculture, Forestry and Fisheries (MAFFJ ), and presented in this paper. In addition to the above-mentioned three major tuna fisheries, there are miscellaneous gears catching tunas. Among them, the largest catch is made by the coastal troll fishery whose recent annual catches are about 10,000 MT, 2,000 MT and 300 MT for skipjack, yellowfin and bigeye, respectively. Remaining catches other than this fishery is very minor. 2. Trends in fleet size Table 1 and Fig. 1 show the historical changes in number of Japanese tuna boats actually engaged in fishing by type of fishery and vessel size class. Data are available since 1953 (MAFFJ ). For the longline fishery, larger than 100 GRT vessels includes those operated in the outside of the WCPO, but currently there is very few GRT boats operating in the outside of WCPO. Most of the boats larger than 200 GRT are operating in the waters outside of WCPO. All other categories operated in the WCPO. The number of longline vessels of the largest size class (over 200 GRT) had been nearly constant since the late 1960s except in 1982 and 1999 when a reduction of fishing vessels took place by about 20 % of that category. The latter reduction was implemented in accordance with the agreement at the FAO s International Action Plan on management of fishing capacity. Vessels of the other categories indicated considerable fluctuation up until the early 1980s but all indicated strong decline at least during the last 13 years. The vessels of GRT disappeared in recent years. The total number of longline vessel in 2002 was 1442 which is 421 vessels (23 %) less than that of 10 years ago. In the case of pole-and-line boat, all size classes exhibited a considerable decline including the largest size category, in which case it was 279 in 1975 but now there is only 48 vessels left. Similar to longline vessel, GRT size vessels were nearly eliminated from the fishery in recent years. On the contrary, GRT class vessels are gradually increasing after a sharp drop which took place in the 1970s. Total number of vessels larger than 20 GRT in 2002 was 152, 86 vessels or 30 % less than that of 10 years ago. Purse seine vessels, which operate in the equatorial waters of the western and central Pacific, are greater than 200 GRT (most of them are 349 GRT), and GRT class boats operate in nearshore Japan north of 20N. While the number of vessels of the latter size category decreased during the late 1980's, there has been no change in recent 7 to 8 years. The number of distant water purse seine is 35 in 2002, which has been nearly stable from the early 1980's. 3. Trends in catch and effort Longline fishery Latest available statistics are provisional 2003 data for those boats larger than 20 GRT. Fishing effort and catch in number and weight of tunas (albacore, yellowfin, and bigeye tunas), swordfish and billfishes (striped marlin, blue marlin, black marlin, sailfish and shortbill spearfish) caught by the Japanese offshore and distant water longliners in the WCPO are shown in Table 2, Figs. 2 and 3 for the years Since the major vessel size in the WCPO is GRT class, the annual trends in fishing effort and catch were similar to the trends in the number of boats of that category. However, the decline of catch for that category was less pronounced as the smaller boats in the same category have been eliminated. Total longline fishing effort (in number of hooks) has decreased steadily since a peak in 1981 (Fig. 2, bold line at the upper panel). The fishing effort in 2003 was 126 million hooks which is 23 % lower than 10 years ago. The area of effort reduction appeared to have occurred in the waters around Japan and western tropical Pacific as shown in Fig. 2. Among the species caught, albacore and swordfish did not show any decline while the other 1

4 species indicated continuous reduction especially after The yellowfin catch was at a peak during the late 1970s and the early 1980s and started going down soon after. Bigeye catch followed this trend in more recent years beginning in the early 1990s. The billfish catch more or less reflected the decreasing trend in the fishing effort. Annual distributions of fishing effort for 1960, 1970, 1980 and 2002 are shown in Fig. 4 and the quarterly effort distribution in 2002 is shown in Fig. 5. The fishing effort has been located in the wide area of the WCPO except for south of 10S and east of 180 meridian. The fishing grounds are located in east-west direction off Japan to Hawaii, equatorial area between 10S and 15N and off Australia. Recent annual and seasonal patterns in the effort distribution have not changed so much, but the overall area of fishing appeared to be contracted and the fishing effort in the western side (west of 150E) have shown a large reduction. Distributional patterns of the catch by species for boats larger than 20 GRT (Fig. 6) are shown for the entire Pacific, and they are classified into several clear patterns (swordfish targeting near Japan, albacore targeting in the middle latitudes between 10-30N and tropical tuna (mostly bigeye) targeting in the equatorial waters). Catch composition for this fleet and that for boats smaller than 20 GRT in 2002 (Fig. 7) indicated that the largest component was bigeye (44% and 36%, respectively) followed by yellowfin (22% for both) and albacore (19% and 20%). These tunas accounted for nearly 85 % of the total catch. Geographical distribution of fishing effort and catch composition for the coastal longliners (less than 20 GRT) were shown in Figs. 8 and 9. Fishing area is more confined to the western Pacific and north of the Equator than the larger longliners in size. The catch composition indicated that the proportion of swordfish appeared to be higher and bigeye is lower (Fig. 7) in this component of the longline fishery especially in the nearshore of Japan Pole-and-line fishery The catch and effort statistics in the WCPO by the Japanese pole-and-line fishery (larger than 20 GRT in vessel size) are shown in Table 3 from 1972 to Catch and effort decreased gradually throughout 1980s with a peak being around the late 1970s. After 1991 they were almost stable. Total yearly catches in 1970s and early 1980s were from 250,000 to 300,000 MT and were around 150,000 MT in 1990s and later. Skipjack occupied the major part of catches being followed by albacore and yellowfin. Number of fishing days exceeded 60,000 days in 1970s but it is now slightly over 20,000 days. Number of poles used also peaked at 1977, and were more than 1,200,000 before 1982 except in Then, it decreased to 400,000 poles level during the 1990s and thereafter. In 2002, the number of fishing days and poles decreased slightly from Total catch in 2002 was higher than those in previous years amounting at 144,637 MT (Table 3). Catches of skipjack, yellowfin and bigeye tunas in 2002 were 90,466 MT, 2,501 MT and 1,714 MT, respectively (Table 3). Skipjack and yellowfin catches were lower than those in On the other hand, albacore catch increased to 49,433 MT, 1.7 times higher than that in Seasonal fishing ground movement was shown as the distribution of fishing effort (the number of poles in 1x1 degree area) in 2002 by quarter (Fig. 11). The fishing grounds move from southwest of Japan to northeast as the time progresses. In addition to these fishing grounds around Japan, north of the North Equatorial Current area was also important fishing ground for this fishery in 1st, 2nd, and 4th quarter of the year. In 2nd and 3rd quarter fishing grounds off northern Japan expanded to further east of 175E. There was no operation in the tropical waters south of 20N in the 3rd quarter. Typical seasonal fishing ground by vessel type was as follows; The distant water vessels (larger than 300 GRT) fish in the tropical waters and the North Equatorial Current area from late 4th quarter to early 2nd quarter, and turn to far north to the area east of 150 E where they target on albacore during June to October. Fishing ground in sub-tropical area east of northern Mariana Islands was the starting area of fishing for the greater part of the offshore vessels (smaller than 300 GRT) in February. Then, this fishing ground gradually moves northward in May and June, and the nearshore area just southeast of Tokyo forms a good fishing ground for these vessels. From July to December, off northern Japan 35N-41N west of 155E, so-called Tohoku area, becomes a major fishing ground around Japan. The fishing ground in the Nansei Islands, southwest of Japan is for the other offshore vessels operating with anchored FADs. The Izu Islands area, south of Tokyo is also fished by some offshore vessels. Almost all fishing ground except for further northeastern area, skipjack has been the major target species and most of the yellowfin catch comes from the Nansei Islands area Purse seine fishery This fishery had started on an experimental basis during the late 1960s, and has expanded over the following 20 years (Table 4 and Fig. 15). The majority of the catch has been skipjack which accounted for more than 70% of the total catch. Total catch has increased to more than 150,000 MT since 1983 and stabilized to nearly 200,000 MT after Fishing effort (days fishing) has also shown a similar trend but has been stable since Fishing grounds in tropical area during 2003 were formed in east-west direction in the wide area of the WCPO (10S-8N, 135E-180 in Fig. 16). This fishing area was different from 2002 as the fleet operated in the west of 150E during the first half of 2003 with an extraordinary good catch of skipjack. This area has not been fished extensively since During the latter half of the year, most of the effort was exerted in the eastern part of the WCPO between 150E and 180. In the coastal waters around Japan, the fishing season of the Pacific side started in late April around Izu Islands area. Some of the boats operated in the same area together with pole-and-line boats, apparently competing each other. The majority of the catch in this area has been skipjack. 2

5 Geographical distributions of catches for skipjack, yellowfin and bigeye in the equatorial area are shown in Fig. 17. Annual total catch obtained from the logbook in 2003 in the WCPO by this fishery (Table 4) was 179,000 MT, 27,000 MT and 4,700 MT for skipjack, yellowfin and bigeye, respectively. The skipjack catch was the fourth highest (highest in 1998), and bigeye catch was the third highest (highest in 1997), and the yellowfin catch recovered from the lowest since 1979) but still lower than the recent average. This has resulted from the facts that the skipjack has been abundant in the equatorial waters and the yellowfin free swimming schools were not detected by the fleet for the past two years. Since around 1994, skipjack has been caught in significant amount in the waters around Japan fluctuating between 15,000 and 95,000 MT. In 2003, about 50,000 MT of skipjack, 2,950 MT of yellowfin and 930 MT of bigeye were caught in the vicinity of Japan. Traditionally, this fishery utilized tuna schools in association with natural logs (upper panel of Fig. 18), but since around 1999 FADs have been extensively used when and where natural logs were not available. Natural logs were more often observed in the north of the Equator and free swimming schools were found near the Equator (lower panel of Fig. 18). The correction for the species composition through the port sampling indicates that the bigeye catch in the logbook records was underestimated between 10 and 27 % (Table 5) during the past 7 years. The length frequency distribution for 2003 obtained through the port sampling is shown in Fig. 19. For bigeye and yellowfin the majority of the catch was small fish less than about 70cm in fork length. All three species had a clear mode at about 36-40cm, 50cm and cm. Compared to 2002, these locations of mode were somewhat different for all three species. The largest mode of skipjack was 55cm in comparison to 45cm in This shift of strong cohort has been observed since 2001 that was at about 40 cm in that year Catch by other coastal fisheries There are several coastal fisheries that catch tropical tunas. Among them the largest catch has been made by the troll fishery operated in the nearshore Japan. Longline and pole-and-line fisheries operated by 20 GRT boats also take significant amount (Table 6). Other coastal fisheries include small scale purse seine, traps, and gillnet whose total catches are very minor Total catch for tropical tunas for all gears combined Trends of total catch for tropical tunas for all gears combined (coastal longline, pole-and-line, troll and other miscellaneous gears) were shown in Table 7 and Fig. 20 for During this period, bigeye tuna catch has been stable but went down a little since 1993 while the other two (yellowfin and skipjack) species indicated a moderate increase up until the mid 1980s and then declined slightly. The 2002 yellowfin catch was further down and the lowest in this time frame. The 2002 total catch was 36,000 MT, 42,000 MT and 293,000 MT for bigeye, yellowfin and skipjack, respectively. 4. Description of fishing in the western and central Pacific Ocean during 2003 Fishing reports of the Japanese tuna fisheries in the western and central Pacific Ocean in 2003 are briefly summarized below. This information was mainly obtained through the interviews to fishermen at Yaizu fishing port by the NRIFSF staff Longline fishery The longline fishing grounds are generally formed in three latitudinal bands, where the target and species composition are different depending on the season and mode of operation. These bands are located mostly northern latitudes (25-40N), middle latitudes (15-25N) and equatorial area (10S-15N), extending from 130E to nearly date line. Northern latitudes There are three types of fishing currently being conducted whose target species is different (albacore, bigeye and swordfish, respectively). Albacore is actively fished especially near Japan (around Izu Islands) during winter season (Nov.-March). The other two species (bigeye and swordfish) are targeted all year round, in particular in fall to winter in the high latitudes between 30 and 40 N. The swordfish operations are made at night and often accompanied with considerable catch of blue shark. In 2003, the main albacore fishing was located in waters of 28-38N and 132E-170W. The average catch per day was MT (albacore CPUE=3-6%) and lower than the previous year. Bigeye CPUE was similar to the last year. Albacore, swordfish and striped marlin are also caught in those sets. Middle latitudes The major fishing area are formed both western and eastern sides of Mariana Islands. Majority of catch were large albacore of 6-7 age old with minor catches of bigeye, yellowfin and blue marlin. In general, fishing was a bit better during the first half of the year (average catch was 1.2 MT), but slightly worse ( MT) during the second half of the year. 3

6 Equatorial area Fishing grounds in this area are located near Nauru, Marshall Islands and Kiribati where bigeye and yellowfin are the major components. Average catch were between 1.0 and 1.5 MT per set. Bigeye (>25kg) and yellowfin (>15kg) accounted for the most of catch with minor amount of blue marlin. Large albacore (>20kg) was also caught in the northern and southern edge of this area. It was reported that there were many longliners from different nations such as Korea, Taiwan and Mainland China. Johnston Islands The southern waters of Johnston Islands and Hawaii were fished by larger longliners with distant water license. The catch-per-day was 1.2 MT during the first half of 2003 and went down to 0.9 MT in the second half. Major component of the catch was bigeye. Many foreign longliners were often sighted, and it was reported that there were many competitions among boats where to set the gears. Eastern Pacific Ocean (ETP) The fishing was relatively fair (0.7 MT/day) at the beginning of the 2003 and became a bit slow (0.6 MT/day) during the second half of Average catch-per-day was lower in the western side of ETP. In general, fishing became poorer than Pole-and-line fishery 2003 P&L fishery In st quarter, fishing ground of distant water vessels started in the Solomon Island area (12-14S, E) and moved to the northern hemisphere of 2-9N, E. The fishing ground moved north and westward in March and April to the area north of Guam (19-21N, E). The main fishing ground in May were east of the Truk Island (7-12N, E) and east of the Mariana Islands (19-25N, E) and at late May some vessels moved into northern area of 33N, 157E to search albacore. From June to October, vessels operated in the Kuroshio extension area (36-37N, E) and the Emperor Sea Mount area (35-40N, E) to catch mainly albacore. Good fishing ground was not formed in September of this season, the majority of catch was consisted of skipjack. Total estimated albacore catch by distant water pole-and-line vessels was about 28,000 MT and decreased to the catch level in In late November all vessels moved southward and into the fishing ground around the Mariana Islands and Marshal Islands. In December they moved to further south in the Solomon Islands area. Fishing ground for offshore vessels from the January to March in 2003 continued at the Northern Mariana and the Bonin Islands areas (21-28N, E). Then the fishing ground in April and May were closed to Japanese coast near the Izu Islands of 33-36N, E. Catch per a vessel-day in 2003 were higher than average value of recent 12 years during March and June. In the beginning of the 2nd half of the year, the skipjack fishing ground for offshore vessels formed near 150E. And then vessels moved to the north and north-westward off the Pacific coast of the northern Japan to 42N in September. This fishing ground disappeared in November. Total estimated landing of offshore vessels in 2003 was at the average level skipjack catch in coastal area by coastal pole-and-line fishery (less than 20 GRT) and troll fishery was same level as the average. The quarterly length frequency distribution of pole-and-line caught skipjack in 2003 obtained through the port sampling was shown in Fig. 13. This covers major fishing port for coastal and offshore fisheries and some part of distant water fisheries operating in the Northwestern Pacific (north of 25N). 2nd and 3rd quarters were high season around Japan and majority of catch was composed of cm in the 2nd quarter and growing up to cm in the 3rd quarter P&L fishery Distant water vessels continued operating in the Solomon Islands area in January through March They moved to the area east of Guam Island of the north equatorial current (7-13N, E) in April and operated in that area and the area in the subtropical countercurrent near the Mariana Island (18-19N, E) in May. Then they shifted to further north at the water around the Izu Islands in late May and moved into the Kuroshio extension area west of the Emperor Sea Mount area (35-37N, E) to catch mainly albacore. Although offshore vessels started their 2004 fishing season at the subtropical countercurrent and moved gradually northward as usual in February, a big albacore fishing ground was formed close to Japan (34N, 139E) in early April and offshore pole and line vessels moved into this area continued to catch albacore together with skipjack through early June. Therefore catch amount of skipjack by offshore vessels in first half of 2004 was less than the average. On the other hand, albacore catch was the highest record catch in recent 23 years. In June and July, the major part of the skipjack school are distributed around 150E where is relatively offshore because of the distribution of the cold eddy from the Oyashio current near the coast of northern Japan. Catches of coastal fisheries such as coastal pole-and-line smaller than 20 GRT and troll were lower than average level throughout of Pacific coast of southern and western Japan in 2004 so far Purse seine fishery 4

7 2003 fishing is characterized by the significant activities in the waters west of 140E since This fishing area was fished especially during the second quarter and the east of 160E became the major fishing area during the second half of Except for the westernmost fishing zone, the general fishing area was similar to the recent years. Skipjack catch became very good since the mid December of 2002 with some catches of large yellowfin around west of Nauru. This has been often observed that the free swimming schools become available to the purse seiners when the North Equatorial Counter Current became weak. In February, this fishing ground has shifted to the south of Nauru and Truk Island, especially in the latter area where log and FADs sets became popular. The area of fishing moved west and was formed between E in the north of Equator. Free schools and log or FADs sets were targeted in the western part and in the eastern part of this area, respectively. Extraordinary good catch of skipjack was recorded and the price went down to yen per kg. This good catch has continued until June moving further west ( E). Some boats turned to east in June and operated in E mainly on log schools. In August some small skipjack were caught, and the fleet shipped to further east and south. Smaller skipjack were mainly caught and high catches were made in October. Yellowfin were also caught in log or FADs sets during December accounting for 25-35% of the total catch in the south of Equator between Nauru and Kiribati. 5. Research activities related to tuna and billfish in the WCPO Bigeye and yellowfin Tropical tuna tagging project in Japan Tagging project on bigeye and yellowfin was started in 1999 in southern Japan, and is being continued. Major objectives of this project are to provide movements of fish in this area in relation to the surrounding waters, detailed movements around the anchored FADs, information on growth, the degree of exploitation by fishing gear in the area and so on. To date, nearly 1350 bigeye and 5160 yellowfin of 30-65cm in fork length were released, of which 185 bigeye and 530 yellowfin were recaptured. At the same time, archival tagging was also conducted for both species. Although the days at liberty of most recaptures are short, interesting results on the swimming behavior of these species are being gathered. More detail information is given in Matsumoto et al, (2003). Pop-up satellite tagging for medium-sized bigeye ( cm) has begun last year and three fishes were already released in the eastern offshore of Japan in June (33-37N, E) from a commercial longliner. So far no bigeye was released primarily due to the bad fishing in this area. Three pop-up tags will be deployed in the central Pacific from the research longline boat. Verification of otolith daily ring by Oxytetracycline (OTC) injection In order to verify the daily rings on otolith of bigeye and yellowfin tunas, four experiments to rear tunas in captivity were conducted in In 2002, alizarin complexion was used in addition to OTC. As the number of bigeye used for the past experiments was not enough, the experiment is now being repeated only for bigeye. Total of 72 bigeye, whose fork length was 43 to 58 cm, have been kept in a pen after OTC was injected. Of those, 70 % fish were injected twice. These fishes will be retrieved at the end of July and used to verify the daily rings. Study on the swimming behavior of small tunas around the FADs in open ocean In 2001, a research cruise was conducted by the R/V Shoyo maru in the central Pacific. Small tunas were released around the FADs after they were attached with ultrasonic tags. More than 20 individuals were monitored simultaneously and tracked. The results indicated that smaller fish tended to swim shallower layer than the larger ones. To reinforce this result and obtain more observations, another research cruise was conducted in the EEZ of Solomon Islands and further east during the late October to early November in Although the number of fish monitored was fewer but it confirmed that bigeye tended to swim slightly deeper waters than yellowfin but they often swam the similar depth range. It was also indicated the lower depth of the swimming range appeared to be restricted by the water temperature (21 C). Taking into consideration of results of these experiments, it seems difficult to selectively avoid catching bigeye tuna by adjusting the depth of net in tuna purse seining. Stock assessment with Multifan-CL model Collaborative study has been continued among the scientists from SPC, IATTC, US, Japan and others. This year Japan sent scientists to SPC before this SCTB in order to provide an improved abundance indices as well as the most recent stock assessment on Pacific tuna stocks. Improvement of input data, i.e., data processing of the catch and effort as well as size data for the earlier part of the fishery has been mostly completed, and they were used in the current stock assessment Skipjack Skipjack tagging Three research and two training pole and line vessels were involved in the skipjack tagging. In addition, one commercial distant water purse seiner conducted voluntarily tagging throughout of her operations in the temperate water. Total of 2,597 skipjack and one albacore were released in 2003 and 240 skipjack were recovered so far. Of 5

8 these, 198 skipjack were released from the distant water purse seiner and 5 fish were recovered. Tag and releases in the 1st quarter of the year were distributed in the area south of 25N. In 2nd and 3rd quarters, the North western Pacific off Japan was the main area for tagging. Some releases were conducted near Japan in 4th quarter also and there were releasing in the tropical waters in this period, too. Works on skipjack otolith Based on the otolith increments reading method validated (Tanabe et al, 2003a and 2003b), age and growth study was continued for skipjack in the EPO and Indian Ocean as well as the WCPO (Kayama et al., 2004). In order to examine the WCPO skipjack migration pattern in their life history, the strontium (Sr) and calcium (Ca) concentrations in the otoliths were measured (Arai et al., 2004). Sr:Ca ratios of the skipjack otloiths could be used as an environmental indicator to detect the water temperature experienced in their migratory history Swordfish and billfishes NRIFSF conducts some biological studies on billfishes caught in the northwest Pacific. This year s outline is summarized as follows; Size data sampling. Unsexed size data of billfishes caught mainly in the northwest Pacific are collected in major ports of Japan. In 2002, numbers of data for swordfish was about 36,000, and 7,200 for striped marlin and 20 for blue marlin. In addition, sexed size data of swordfish caught by Japanese surface longliners operating in the northwest Pacific, and sexed sized data of blue marlin caught by small trolling boat operating in southwestern part of Ryukyu Islands. Number of sexed size data of swordfish in 2003 was about 8,000, and blue marlin was about 2,000. Tagging study NRIFSF is conducting traditional tagging activities on billfishes in cooperation with longline and sports fishermen. In addition, 5 archival pop-up tags were attached on blue marlin caught by a coastal trolling boat in Two tags were attached in southwestern part of Ryukyu Islands in May, and 3 were attached in the eastern coastal area of Honshu. In 2004, one archival pop-up tag was attached on blue marlin in near shore area of Guam Island and 2 were attached in the southwestern part of Ryukyu Islands. Among these eight pop-up tags applied, archived data of 7 tags were obtained. Total amount of collected data was about 180 days. Cooperative traditional tagging program on marlins between NRIFSF and Japan Game Fish Association has commenced in the spring of Biological study Stomach contents analysis is being conducted for swordfish caught by the Japanese offshore longliners, and for blue marlin caught by the coastal trolling boats. Aging study for blue marlin caught in near shore Japan is also commenced in collaboration with a university. References MAFFJ Annual report of catch statistics on fishery and aquaculture, Statistical and Survey Division, Ministry of Agriculture and Forestry. Arai, T., A. Kotake, S. Kayama, M. Ogura, and Y. Watanabe. (2004): Movements and stock discrimination of skipjack tuna, Katsuwonus pelamis, in the western Pacific by otolith Sr:Ca ratios. SCTB17 Kayama, S, T. Tanabe, M. Ogura, H. Okamoto, and Y. Watanabe (2004): Daily age of skipjack tuna, Katsuwonus pelamis (Linnaeus), in the eastern Indian Ocean. IOTC-2004-WPTT-03. 6p. Matsumoto, T., Okuhara, M., Ohta, I., Mizoguchi, M. and Miyabe, N. (2003): Report of the ongoing tagging project on tropical tunas around Japan. SCTB16/RG pp. Tanabe T, Kayama S, Ogura M. Tanaka S. (2003a): Daily increment formation in otoliths of juvenile skipjack tuna Katsuwonus pelamis. Fisheries Sci. 69: Tanabe T, S. Kayama, and M. Ogura (2003b): Precise age determination of young to adult skipjack tuna (Katsuwonus pelamis) with validation of otolith daily increment. SCTB16 SKJ-8. 10p 6

9 Table 1. Number of fishing vessels engaged in tuna fisheries in the Pacific Ocean by type of fishery and size of vessel. Year/ Size class 1-19 GRT GRT Longline fishery * GRT GRT 200- GRT Total GRT *2 GRT Pole-and-line fishery GRT GRT GRT Total 199 GRT Purse seine fishery (18) (35) (53) *1 Boats larger than 50 GRT include those operated in the area other than the Pacific. *2 Number of 1-19 GRT class boat for does not includes boats less than 10 GRT, and boats before 1995 include those boats engaged in trolling. *3 Figures in the parentheses indicate provisional data GRT Total 7

10 Table 2. Fishing effort (in million hooks) and catch (number in thousands and weight in MT) in the WCPO by species for the Japanese longline fishery (boats larger than 20 GRT). FAO s species codes are used to express species name. Number of fish Weight Year Hooks ALB BET YFT SWO MLS BUM BAM SAI SSF ALB BET YFT SWO MLS BUM BAM SAI SSF Total ,431 28,959 34,908 6,213 6,135 8,225 1, , ,030 30,126 29,974 7,131 4,816 4,709 1, , ,101 39,658 29,677 6,555 3,455 6, , ,161 28,231 30,906 5,792 3,766 5, ,128 88, ,467 32,132 33,899 6,339 3,475 5, , ,622 32,148 28,921 6,682 2,233 3, , ,738 38,786 32,521 7,859 2,112 3, , ,782 41,843 43,950 7,752 1,505 4, , ,636 35,456 62,622 7,937 2,033 5, , ,799 37,173 50,879 8,803 3,574 4, , ,821 35,599 63,289 6,573 3,393 6, , ,025 28,390 53,594 7,956 3,081 5, , ,273 32,714 46,205 6,894 3,093 5, , ,335 28,998 47,526 7,942 2,094 4, , ,216 31,508 36,669 7,583 2,787 6, , ,688 33,348 38,278 10,223 3,653 5, , ,493 29,825 29,968 9,414 4,397 5, , ,516 38,429 28,045 9,493 2,809 3, , ,166 29,331 33,021 9,641 4,763 4, , ,273 32,189 25,639 6,897 3,836 3, , ,045 37,117 26,862 6,404 2,334 2, , ,985 25,507 19,221 5,315 2,532 2, , ,494 30,852 24,067 8,821 2,331 2, , ,376 25,795 24,052 9,194 3,228 3, , ,239 23,090 24,451 8,319 2,937 3, , ,522 19,747 25,189 6,974 3,058 3, , ,794 16,565 20,422 7,470 2,078 1, , ,495 21,471 17,370 7,616 1,668 1, , ,770 25,549 14,960 6,730 2,169 1, , ,476 21,911 11,120 5,895 1,444 2, , ,411 19,187 18,716 5, , , ,179 20,219 11,239 5,769 1,034 1, , ,429 24,488 12,297 6, , , ,258 20,573 12,501 5,466 1,332 1, ,220 8

11 Table 3. Days fished, number of poles used, and catch (MT) by species for the Japanese pole-and-line fishery (larger than 20GRT) in the WCPO. Number of Number of Catch in MT Year fishing days poles Skipjack Yellowfin Bigeye Albacore Others Total ,657 1,099, ,976 5,544 1,627 48,578 2, , ,750 1,226, ,285 6,057 1,149 61,168 2, , ,740 1,201, ,455 4, ,828 2, , ,920 1,168, ,093 5,420 1,281 47,660 2, , ,090 1,270, ,015 7,351 3,313 78,451 3, , ,988 1,540, ,406 9,906 3,231 34,953 1, , ,793 1,375, ,267 7,633 3,183 56,658 1, , ,418 1,277, ,911 5,836 2,140 44,982 2, , ,432 1,185, ,542 6,191 1,994 43,020 3, , ,430 1,211, ,719 9,054 2,338 25,599 3, , ,853 1,084, ,154 9,499 3,810 28,822 3, , , , ,530 9,338 3,772 19,596 3, , , , ,495 8,702 3,211 25,920 2, , , , ,175 12,925 3,981 21,039 3, , , , ,723 8,410 2,519 13,820 2, , , , ,518 8,454 2,816 19,054 2, , , , ,004 8,129 3,660 7,130 2, , , , ,137 9,146 3,570 10,919 2, , , , ,391 6,970 3,331 13,820 3, , , , ,338 5,404 1,232 6,469 2, , , , ,649 6,904 1,028 14,856 3, , , , ,403 4,529 1,770 12,471 1, , , , ,944 4,035 1,908 30, , , , ,620 4,527 2,627 22,828 1, , , ,328 97,916 4,883 2,549 22, , , , ,500 3,727 2,584 34, , , , ,191 3,062 1,352 27,689 1, , , , ,290 3,646 1,097 54, , , , ,860 3,475 1,792 21, , , ,319 96,144 2,616 1,321 29,225 1, , , ,937 90,466 2,501 1,714 49, ,637 9

12 Table 4. Days fished and catch (MT) by species for the Japanese tuna purse seine fishery (larger than 100 GRT) in the WCPO based on logbook data. Others include other tuna and tuna-like species. Year Days fished SKJ YFT BET Others Total ,028 8,221 3, ,423 16, ,561 12,311 5, ,515 20, ,723 13,616 7, ,245 23, ,998 5,886 9, ,860 17, ,265 7,275 5, ,766 18, ,529 17,741 7, ,747 28, ,232 18,498 6, ,100 31, ,429 25,821 8, ,013 44, ,622 28,760 19, ,870 61, ,716 48,820 20, ,206 81, ,736 44,773 27, ,005 98, ,103 75,152 31,098 1,131 17, , , ,038 30,830 1,468 14, , , ,975 38, , , , ,204 47,941 1,381 7, , , ,900 44,467 1,531 8, , , ,455 44,634 1,602 11, , , ,673 30, , , , ,041 40,872 1,528 8, , , ,134 37,757 2,122 6, , , ,156 48,598 1,951 8, , , ,177 53,099 2,563 8, , , ,889 57,858 1,903 5, , , ,151 39,866 1,676 10, , , ,179 45,183 1,629 14, , , ,177 24,539 1,494 6, , , ,904 57,475 8,467 12, , , ,247 37,712 2,706 4, , , ,321 43,847 3,523 20, , , ,638 36,590 4,779 19, , , ,380 33,737 6,131 10, , , ,052 19,138 4,587 13, , , ,375 26,592 4,689 7, ,026 * Based on logbook data. Table 5. Comparison of species composition between landing and corrected statistics through the port sampling for the Japanese purse seine fishery (equatorial fishery), (unit=mt). Landing Estimated by port sampling Year SKJ YFT BET Total SKJ YFT BET Total ,047 26,889 1, , ,278 25,424 2, , ,805 49,665 11, ,109 84,732 49,745 13, , ,378 37,723 4, , ,693 35,793 4, , ,017 43,304 4, , ,600 42,520 5, , ,087 37,960 6, , ,553 35,438 8, , ,030 43,074 8, , ,004 42,080 9, , ,287 22,585 4, , ,287 21,297 5, , ,834 29,955 3, ,610 10

13 Table 6. Catch statistics of major tuna species for coastal and other miscellaneous gears. All these gears were operated by the small boats less than 20 GRT. More than 90 % of the catch by other fisheries has been made by troll fishery. Year Coastal LL Coastal PL Bigeye Yellowfin Skipjack Other PS Other fisheries Total Coastal LL Coastal PL , ,347 1,287 8, ,237 4,321 6,670 17, , , , , ,301 8, , , , ,243 17, ,084 2, , , , ,243 18, , ,284 2, , , ,112 19, , ,425 5, , , ,646 14, , ,166 7, , , ,047 17, , ,755 7, , , ,146 19, , ,477 7, , , ,296 28, , ,858 6, ,420 9, , ,198 20, , ,793 5, , , ,472 22, , ,732 5, , , ,599 19, , ,185 5, , , ,590 24, , ,428 6, ,900 1,134 12, ,301 26, , ,336 5, , , ,912 25, , ,956 6, , , ,478 17, , ,856 6, , , ,863 29, , ,282 7, , , ,469 21, , ,493 7, ,346 9, , ,393 29, , ,853 7, ,399 9, , ,300 23, , ,301 7, , , ,217 25, , ,514 8, ,293 9, , ,757 26, , ,970 8, ,548 10, , ,040 22, , ,057 7, ,706 9, , ,886 21, , ,470 6, ,476 8, , ,999 14, , ,135 6, ,550 8, , ,909 20, , ,803 6, ,616 8, , ,369 13, , ,104 6, ,083 8, , ,951 16, , ,308 5, ,043 8, , ,718 16, , ,179 5, ,974 10, , ,391 14, , ,371 6, ,421 9, , ,528 25, , ,854 5, ,136 9, , ,810 16, , ,148 4, ,841 8, , ,756 14,909 Other PS Other fisheries Total Coastal LL Coastal PL Other PS Other fisheries Total 11

14 Table 7. Japanese total catches (all gears combined) for tropical tuna species. Year BET YFT SKJ Total ,292 45, , , ,646 49, , , ,714 51, , , ,119 46, , , ,655 56, , , ,131 69, , , ,724 87, , , ,891 84, , , ,950 97, , , ,385 96, , , ,838 93, , , ,666 94, , , ,758 91, , , , , , , ,731 90, , , ,128 89, , , ,090 80, , , ,140 85, , , ,872 80, , , ,204 82, , , ,413 94, , , ,524 96, , , ,144 77, , , ,139 83, , , ,411 58, , , ,626 87, , , ,904 64, , , ,388 68, , , ,130 68, , , ,525 57, , , ,937 42, , ,571 Table 8. Number of fish released and recaptured in the tropical tuna tagging project conducted in the Nansei Islands area (Okinawa and Amami Islands). Dart tag Species Bigeye tuna Yellowfin tuna Total Year Rel. Recap. % recap. Rel. Recap. % recap. Rel. Recap. % recap % % % % % % % % % % % % Total % % % Archival tag Species Bigeye tuna Yellowfin tuna Total Year Rel. Recap. % recap. Rel. Recap. % recap. Rel. Recap. % recap % % % % % % % % % % % % Total % % % 12

15 Longline Boats by Size Class (GRT) Pole-and-Line Boat by Size Class (GRT) Fig. 1. Trend of fleet size for longline and pole-and-line boats by size (GRT),

16 Longline fishing effort by area , , ,000 Catch by Species Hooks Total Hooks Catch (MT) 80,000 60,000 40, , Year Japan Japan East Year Hawaii North Total Total ALB BET YFT Hooks Longline fishing effort by area Equatorial west Year Solomon Johnston South Fig. 2. Trend of fishing effort (hooks) for the Japanese offshore and distant water longline fisheries by area. Area definition is as follows : Japan : 20-45N, E, Japan East : 20-45N, 165E-175W, Hawaii North : 20-45N, W, Equatorial West : 15S-20N, E, Solomon : 15S-20N, 165E-175W, Johnston : 15S-20N, W, South : 40S-15S, 145E-150W. Catch (MT) 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 Catch by Species Year SWO MLS BUM Total 140, , ,000 80,000 60,000 40,000 20,000 Fig. 3. Trend of catches (MT) for the Japanese offshore and distant longline fishery by major species. 0 Total (MT) 14

17 Fig. 4. Past distribution of fishing effort for the Japanese offshore and distant water longline fisheries in the western and central Pacific Ocean, 1960, 1970, 1980 and Fig. 5. Quarterly distribution of fishing effort for the Japanese offshore and distant water longline fisheries in the western and central Pacific Ocean in

18 Fig.6. Distributions of offshore and distant water longline catch (weight) by species in for five main species (ALB:albacore, BET:bigeye tuna, YFT: yellowfin tuna, SWO: swordfish and BUM: blue marlin). SWO 11% MLS 1% BUM 3% ALB 19% SWO 18% MLS 1% BUM 3% ALB 20% YFT 22% BET 44% YFT 22% BET 36% Fig.7. Overall catch composition for offshore and distant water longline fisheries (left) and coastal longline fishery (right) in (ALB:albacore, BET:bigeye tuna, YFT: yellowfin tuna, SWO: swordfish, MLS: striped marlin and BUM: blue marlin) 16

19 Fig. 8. Distribution of fishing effort for the Japanese small scale longliners (less than 20 GRT) in the western Pacific Ocean. Data are aggregated for 2000 to Fig.9. Distributions of catch (weight) by species for small scale longliners in for five main species (ALB:albacore, BET:bigeye tuna, YFT: yellowfin tuna, SWO: swordfish and BUM: blue marlin). 17

20 Fig. 10. Trends of fishing effort and catches by species for the Japanese pole-and-line fishery (>20GRT) in the WCPO. 18

21 Fig. 11. Annual distribution of fishing effort for the Japanese pole-and-line fishery (offshore and distant water licenses) in the Pacific Ocean in 1975, 1985, 1995, and Fig. 12. Quarterly distribution of fishing effort for the Japanese pole-and-line fishery (offshore and distant water licenses) in the Pacific Ocean in

22 3,000 2,000 1, ,000 2,000 1, ,000 2,000 1, ,000 2,000 1,000 0 Fig.13. Distribution of pole-and-line catch in 2002 for skipjack (top) and yellowfin tune (bottom). Fig. 14. Quarterly length frequency distribution in 2003 for pole-and-line (coastal, offshore, and distant water) caught skipjack in the northwestern Pacific, north of 25N. 20

23 Fig. 15. Trends of fishing effort and catches by species for the Japanese tuna purse seine fishery in the WCPO. 21

24 Fig. 16. Annual (top) and quarterly distributions (lower four panels) of fishing effort for the Japanese tuna purse seine fishery (larger than 100 GRT) in the Pacific Ocean in

25 Fig. 17. Distribution of purse seine catch (MT) by species (lower panel) combined for Set type was classified as free swimming, natural log and FADs schools Number of Sets Free Log FADs Monthly sets by type of school Fig. 18. Trend of monthly number of sets by type of association and sets by type of school since 1993 (upper) and distribution of sets by type of school for deployed by the equatorial tuna purse seine fishery by Japan. 23