1. Ryuji Yukami‧Seiji Ohshimo‧Mari Yoda‧Yoshiaki Hiyama
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
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. TAC Chub mackerel (Scomber japonicus)
Pacific stock
Tsushima Current stock
Spotted mackerel (Scomber australasicus)
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 maturation and spawning grounds of the two stocks
necessary for understanding of the fluctuation in recruitment as well as a basis for stock management.
we analyzed biometric data and catch statistics in order to elucidate the biological characteristics, especially the spawning grounds, of chub and spotted mackerel.
discuss the factors affecting the fluctuation of the two stocks.

5. Materials and methods Data Gonadosomatic index (GSI)
Biometric data
Gonadosomatic index (GSI)
histologically examined
Catch statistics
CPUE
SST

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 gonad weight (g)  0.1 g
Total number of specimens measured
3,439 for chub mackerel
3,886 for spotted mackerel
GSI
Fork length

8. 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
STEP4
Sectioning
thick
STEP3
Embedding
Paraffin wax
STEP2
Dehydrating
STEP1
Fixing
10% formalin

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 statistics(CPUE)
Assumed
Calculated CPUE for every 0.5° grid point monthly
The monthly CPUE data were averaged
at each grid point from 1992 to 2006
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.
Catch Data

12. Catch statistics(SST)
SST Data
used SST data for every grid point separated by 0.5° in latitude and longitude
Calculated the averaged monthly SST distribution from 1992 to 2006
provided by the Japan Fisheries Information Service Center (JAFIC).

13. Estimation of spawning ground
Results
Estimation of spawning ground
Reproductive
characteristics

14. Relationship between GSI and developmental stage
Postovulatory
follicles
 Matunity ogive of female.

15. Relationship between fork length and GSI
FL >310mm
GSI > 2.5
FL >275mm
Relationship between SST and GSI.
GSI > 2.5
SST ℃
GSI > 2.6
SST: ℃

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

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

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

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

20. Sexual maturation(GSI)
GSI at oocytes with tertiary yolk globule stage
Previous Studies
Our Result
GSI >2
No reports
GSI >2.5
GSI >2.6
Chub Mackerel
Spotted
Mackerel
Yamada et al.(1996)
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 > 300mm
(sample >280mm)
FL > 275mm
FL > 310mm
Chub Mackerel
Spotted
Mackerel
Ouchi and Hamaski (1979)
Tanoue (1966)
Small Change

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

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

24. Spawning ground Previous Studies: Present Study:
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. Changes of suitable areas for spawning
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 does not affect the extent of spawning grounds of chub and spotted mackerel
the relationships between SST and growth rates during the early life stages of chub and spotted mackerel may be focused on.
Expansion
spawning success
Reduction

27. Hiyama et al. (2002): Yukami et al. (2008):
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 spotted mackerel has shown a gradual increase while that of chub mackerel a gradual decrease because of gradual increase of SST in the East China Sea.

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

29. Thanks for
your attention