OVERVIEW OF THE PACIFIC BLUEFIN ・Biological information ・Status of fisheries ・Data collection ・Management of the stock

By Naozumi Miyabe (Speaker: Takayuki Matsumoto) National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Japan Migrations of Juveniles by archival tagging experiments Distribution and migration Spawning Ground transoceanic Movements of spawners and north-south by PSAT tagging experiments

Distribution: Mainly in the north Pacific, especially coastal area and around sea mounts. Spawning: Known to occur off Okinawa to eastern offshore of and Philippines. In the north, western part of . Migration: A part of 0-2 years old fish makes transoceanic migration and reach off Baja California. They return to western Pacific after several years. A certain amount of large fish distributes off eastern Australia and around NZ, therefore, it is assumed that not all the adult fish every year. Season of transoceanic migration

100

120 140 Eastern Pacific 160

180 227 Longitude 160200 241 668 220 1053 140 1058 240 1562 120 Western Pacific 260 100 1 3 5 7 9 11 1 3 5 7 9 11 Month Known movements around Japan

Sea of Japan East China Pacific Sea Ocean Migration and oceanographic condition

SST

SSC

SST+SSC

(Segawa et al., 2002) Changes in water temperature at 50m depth in western Japan Sea Jan‐Mar Apr‐Jun Anomaly (℃)

Jul‐Sept Oct‐Dec

Green lines indicate observed anomaly and red lines are 3‐year moving average. Position of Western Japan Sea

Area of estimation of 50m depth temperature

Northern Japan Sea

Western Japan Sea Geographic distribution of purse seine catches In Japan Sea, 1993 and 1995

1993

1995 Geographic distribution of purse seine catches In Japan Sea, 2000

Quarter 1 Quarter 2

Quarter 3 Quarter 4 Geographic distribution of purse seine catches In Japan Sea, 2006

Quarter 1 Quarter 2

Quarter 3 Quarter 4 Geographic distribution of purse seine catches In Japan Sea, 2007

Quarter 1 Quarter 2

Quarter 3 Quarter 4 Growth Equation by Bertallanfy

Lt = 242{1−exp[−0.198 (t+0.376)]} 300 n = 460, r 2 = 0.960

250 Max 200 Age 18 （240 cm） 150 Age 10

FL（ｃｍ） About 210 cm 100 Age 5 About 160 cm 50 Shimose pers.com.

0 0 5 10 15 20 Age 98 cm Sectioned Otolith Age 2

157 cm Age 5

240 cm Age 18

1 mm Maturity 2 1

Ratio of maturity 0.8 1.5 0.6 1 Ｍ 0.4 0.5 0.2 Natural mortality 0 0 of maturity Ratio 0123456789 Age in year M: ＩＳＣ(2007) Start of maturity •150cm (5 years old) in the Pacific Ocean •120cm (3 years old) in the Sea of Japan, and most of the fish mature after 5 years old. Distribution of and catch amount by Japan 40 35 Purse seine Set net 30 Purse 25 seine 20 15 Longline 10

Troll Troll Catch(1,000MT) 5 0

Longline 52 55 61 64 67 70 73 76 82 85 88 91 94 97 03 9 9 958 9 9 9 9 9 9 979 9 9 9 9 9 9 000 0 06* 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 0 Purse Seine Year 2 Longline Trolling Set net Purse seine Longline Troll Pole and line Set net Others * Data for 2006 are preliminary **In addition, it is estimated that 10-20 MT of fish are used for farming • activities are concentrated around Japan. • BFT is caught by longline, purse seine, troll, pole and line, set net, drift net, etc. • Many fishers operate small scale fishery such as troll and handline throughout Japan, therefore it is not easy to collect catch and effort data. • Size of the fish, fishing ground and fishing season differ depending on fisheries. • Purse seine, troll and longline are main fishing method. Fishing season and size of fish caught by the Japanese fishery Fishery Fishing season Fish size Purse seine (tuna) June-October 2-7 years old, 70-170cm

Purse seine (small All year round 0-2 years old, 40-80cm )

Longline Spawning season 5 years or older, >150cm (May – June) in spawning area Troll Summer to winter 20-60cm, occasionally large fish Pole and line Mainly 0 year old fish Set net Summer to winter 0-4 years old fish 40-130cm Drift net Winter to spring Mainly 0-1 year old fish Handline Autumn to spring Small to large fish Distribution of BFT catch by Japanese longline (1994-) by month (Ichinokawa, pers. com.) Change in species composition by Japanese longline (Oshima, pers. com.) Hooks per basket 3-4 5-6 7-12 13-22 Area 1

Area 2

Area 3

Area 4 Change in JPN LL effort, catch and CPUE

Number of operation Effort (number of hooks)

Catch number of BFT CPUE Catch by country • Chinese Taipei: Mainly small longline Japan Korea in the spawning Chinese Taipei USA Mexico Others ground. 45 • Korea: Mainly purse 40 seine in the Sea of 35 (1,000MT) Catch Japan. 30 25 • USA: Purse seine, 20 sport fishing around 15 10 California. 5 • Mexico: Purse seine 0 around Baja California. 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004

In recent years, Japanese catch accounts for 60 to 80% of total catch. US declined recently. Mexico developed farming fishery and the catch has increased. Japanese troll fishery NZ Sport Fishing Size of the fish caught

Proportion of catch in number of fish (2002－2004 average) Others USA, Mexico PS Korea PS Adult JPN Troll (5%) JPN PS

In number, majority of the catch is small fish, especially in troll and purse seine fisheries around Tsushima strait in the East China Sea. Dependency of catch on dominant year class Biological Feature (example of LL fishery)

Length (cm) Once the strong year class has recruited, the same year class is continuously caught. Clear correlation between recruitment and spawning stock Spawning stock biomass Recruitment (number of 0 year old fish) 7 60

6 50 Recruitment(million fish) Spawning stock 5 biomass 40 4 30 3 20 2 Biomass(10,000ton) 10 1 Recruitment 0 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 ⇒After large recruitment, biomass of that year class increases thereafter. By monitoring the strength of recruitment, managements can be done based on that information. Trends of CPUE (longline)

Japan LL Coastal Japan LL Offshore Japan LL Offshore Japan LL Offshore

5 Japan LL Offshore Taiwanese LL (rough estimate)

4

3

2 RelativeScale 1

0 1951 1961 1971 1981 1991 2001 Year Trends of CPUE (other fisheries) Data collection for stock assessments General aspect • Small scale local fisheries (troll, set net, handline etc.) account for considerable part of the catch. → Collection of detailed data is not easy. • As for several fisheries, it is difficult to know correct catch and effort, especially the latter. • Biological information (size, growth, maturity etc.) needs to be enhanced.

Uncertainty in stock assessment → National project for data collection Stock assessment Stock assessments are conducted by ISC (International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean)

ISC

Management of stock is conducted by WCPFC and IATTC Stock assessments & Conservation Schedule ＷＣＰＦＣ ＩＳＣ

2008 May-Jun. Stock assessment meeting

2008 Sep. Northern Committee 2008 Jul. Plenary Session Examination of stock Discussion of status of management measure the stock, recommendation of management measure

2008 Dec. Regular session Decision of management measure Thank you for your attention. Any question or comment? Muchas gracias por su atención. ¿Tienen aluguna pregunta o comentario?