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吳欣蓓

Estimation of the spawning grounds of chub mackerel Scomber japonicus and spotted mackerel Scomber australasicus in the East China Sea based on catch statistics and biometric data. 利用漁獲統計與生物測定推測 東海海域白腹鯖與花腹鯖之產卵場. Ryuji Yukami‧Seiji Ohshimo‧Mari Yoda‧Yoshiaki Hiyama

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吳欣蓓

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  1. Estimation of the spawning grounds of chub mackerel Scomberjaponicus and spotted mackerel Scomberaustralasicus in the East China Sea based on catch statistics and biometric data 利用漁獲統計與生物測定推測 東海海域白腹鯖與花腹鯖之產卵場 Ryuji Yukami‧Seiji Ohshimo‧Mari Yoda‧Yoshiaki Hiyama Fish Sci (2009) 75:167–174 吳欣蓓

  2. Introduction 動物界 Animalia脊索動物門 Chordata 輻鰭魚綱 Actinopterygii鱸形目 Perciformes鯖亞目 Scombroidei鯖科 Scombridae 鯖屬 Scomber • Chub mackerel (Scomber japonicus) • Spotted mackerel (Scomber australasicus) • Identified • Morphological & Molecular

  3. Chub mackerel (Scomber japonicus) • Pacific stock • Tsushima Current stock • Spotted mackerel (Scomber australasicus) • Pacific stock • East China Sea stock Fig. 1 Catch of chub mackerel for the Tsushima Current stock and spotted mackerel for the East China Sea stock by Japanese fisheries TAC

  4. no detailed information on the maturationand spawning grounds of the two stocks • necessary for understanding of the fluctuation in recruitmentas well as a basis for stock management. • we analyzed biometric data and catch statistics inorder to elucidate the biological characteristics, especiallythe spawning grounds, of chub and spotted mackerel. • discussthe factors affecting the fluctuation of the two stocks.

  5. Data Materials and methods

  6. Data • Fish Method: Japanese large- and medium-type purse seine • Region: • the East China Sea, • near coastal area of Kyushu and Tsushima Straight. • Time: from January 1998 to December 2006. Fig. 2 Sampling locations of chub and spotted mackerel. Dots indicate the fishing areas of sample caught by the Japanese large- and medium-type purse seiners

  7. Biometric data(metric) • Fork length (mm)  1 mm • body weight (g)  1 g • sex and gonadweight (g)  0.1 g • Total number of specimens measured • 3,439 for chub mackerel • 3,886 for spotted mackerel GSI Fork length

  8. STEP1 Fixing 10% formalin STEP2 Dehydrating STEP3 Embedding Paraffin wax STEP4 Sectioning 8 thick Biometric data(histologically examined) • Removed ovaries of a randomly selected subsample • A total of 312 chub mackerel specimens and 243 spotted mackerel specimens were histologically examined. STEP5 Staining Mayer’s hematoxylin-eosin

  9. Biometric data(histologically examined) • Seven developmental • perinucleolus stage • yolk vesicle stage • primary yolk globule stage • secondary yolk globule stage • tertiary yolk globule stage • migratory nucleus stage • hydrated oocytes • postovulatory follicles GSI & GSI50 Mature

  10. Biometric date(GSI) • YGSI is the percentage mature at GSI • a is the slope, b is the GSI50 • GSI is the gonadosomatic index. To estimate GSI at 50% maturity (GSI50), a logistic function was fitted to the fraction of mature fish per 0.25 GSI interval using nonlinear least-square regression.

  11. Catch Data Catch statistics(CPUE) a grid every 0.5°in latitude and longitude in the East China Sea by the Fisheries Agency of Japan. the value of CPUE represents the distribution density of spawners.

  12. Catch statistics(SST) provided by the Japan Fisheries Information Service Center (JAFIC).

  13. Results

  14. Relationship between GSI and developmentalstage • Postovulatory • follicles  Matunity ogive of female.

  15. Relationship between fork length and GSI GSI>2.6 FL>310mm GSI>2.5 FL>275mm Relationship between SST and GSI. GSI>2.5 SST15-22 ℃ GSI>2.6 SST:17-25 ℃

  16. Monthly change in the GSI Monthly change in the percentage of the ovarian

  17. Estimation of spawning ground (Chub mackerel) Spawning ground 15-22 ℃

  18. Estimation of spawning ground (spotted mackerel) Spawning ground 17-25 ℃

  19. Sexual maturation Discussion Spawning ground Spawning period Our Result V.S Previous Studies Future studies

  20. Sexual maturation(GSI) • GSI at oocytes with tertiary yolk globule stage Previous Studies Our Result GSI >2 GSI >2.5 Chub Mackerel Yamada et al.(1996) No reports GSI>2.6 Spotted Mackerel Insufficient to verify

  21. Sexual maturation(FL & age) • Fork length and age at sexual maturity • The first spawning age was 1 year old. Previous Studies Our Result N:250mm S: 220mm FL > 275mm Chub Mackerel Small Change Ouchi and Hamaski (1979) FL > 300mm (sample >280mm) FL> 310mm Spotted Mackerel Tanoue (1966)

  22. Sexual maturation(Temperature) Previous Studies Our Result 20.8-24.2 ℃ 15-22 ℃ Chub Mackerel Murata et al.(2005) Main: 17-18 ℃ End: 20-22 ℃ 17-25 ℃ Spotted Mackerel Nashidaet al.(2006) Reasonable

  23. Spawning period Previous Studies Our Result S: Jan to Feb N: Mar to Jun S: No sample N:Feb to Jun Chub Mackerel Ouchi and Hamaski (1979) S: Jan to May S: Feb to May Spotted Mackerel Tanoueet al.(1960) Larve: Feb and Mar Sample too small Ozawa (1984)

  24. Spawning ground • Previous Studies: • only fragmentary information about the spawning grounds of chub and spotted mackerel in the East China Sea. • Present Study: • analyzed biometric data and catch statistics • extensively and continuously • spotted mackerel was in a slightly more southern area than that of chub mackerel • overlapped in the central and southern part of the East China Sea and the area west of Kyushu. Agree with Kijima (1986)

  25. Future studies Changes of suitable areas for spawning Sakurai et al.(2000) Differential optimal temperatures for growth rates during the early life stage Takasuka et al.(2007) V.S

  26. If a gradual increase in SST in the East China Sea • If SST doesnot affect the extentof spawning grounds of chub andspotted mackerel • the relationships between SST and growthrates during the early life stages of chub and spottedmackerel may be focused on. Expansion spawning success Reduction

  27. Hiyama et al. (2002): • Spawning success of the Tsushima Current stock of chub mackerel has been found to be inversely correlated with SST in the East China Sea. • Yukami et al. (2008): • Spawning success of the East China Sea stock of spotted mackerel has been found to be positively correlated with SST in the East China Sea • the stock size of spottedmackerel has shown a gradual increase while that of chubmackerel a gradual decrease because of gradual increase ofSST in the East China Sea.

  28. In the future Stock size Chub mackerel and spotted mackerel in the East China Sea Fishing activities Observed carefully Spawning ground SST

  29. Thanks for your attention

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