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

吳欣蓓

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

IntroductionIntroduction 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 ScomberChub mackerel (Scomber japonicus)Spotted mackerel (Scomber australasicus)Identified◦Morphological & Molecular

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

TACTAC

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.

Materials and methodsMaterials and methods

Data

DataDataFish 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 ofchub and spotted mackerel. Dotsindicate the fishing areas ofsample caught by the Japaneselarge- and medium-type purseseiners

Biometric dataBiometric data(metric)(metric)

Fork length (mm) 1 mmbody weight (g) 1 gsex and gonad weight (g) 0.1 gTotal number of specimens measured ◦3,439 for chub mackerel◦3,886 for spotted mackerel GSI

Fork length

Removed ovaries of a randomly selected subsample

A total of 312 chub mackerel specimens and 243 spotted mackerel specimens were histologically examined.

Biometric dataBiometric data((histologically examinedhistologically examined))

STEP5StainingMayer’shematoxylin-eosin

STEP5StainingMayer’shematoxylin-eosin

m

Biometric dataBiometric data((histologically examinedhistologically examined))

Seven developmental

1. perinucleolus stage

2. yolk vesicle stage

3. primary yolk globule stage

4. secondary yolk globule stage

5. tertiary yolk globule stage

6. migratory nucleus stage

7. hydrated oocytespostovulatory follicles

Mature

GSI & GSI50

Biometric dateBiometric date(GSI)(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.

Catch statisticsCatch statistics (CPUE)(CPUE)

a grid every 0.5° in latitude and longitude in the East China Sea bythe Fisheries Agency of Japan.the value of CPUE represents the distribution density of spawners.

Catch Data

Catch statisticsCatch statistics (SST)(SST)

provided by the Japan Fisheries Information Service Center (JAFIC).

ResultsResults

Postovulatory follicles

Relationship between GSI and developmental stage

Matunity ogive of female.

Relationship between fork length and GSI

Relationship between SST and GSI.

GSI > 2.5FL

>275mm

GSI > 2.6FL

>310mm

GSI > 2.5SST 15-22 ℃

GSI > 2.6SST: 17-25

℃

Monthly change in the GSI

Monthly change in the percentage of the ovarian

Estimation of Estimation of spawning ground spawning ground (Chub mackerel)(Chub mackerel)

Spawningground

15-22 ℃

Estimation of Estimation of spawning ground spawning ground (spotted mackerel)(spotted mackerel)

Spawningground

17-25 ℃

DiscussionDiscussion

Our ResultOur Result

V.SV.S

Previous StudiesPrevious Studies

Spawning period

Future studies

Sexual maturation

Spawning ground

Sexual maturationSexual maturation(GSI)(GSI)

GSI at oocytes with tertiary yolk globule stage

Previous StudiesPrevious Studies Our ResultOur Result

GSI >2GSI >2

No reportsNo reports

GSI >2.5GSI >2.5

GSIGSI >2.6>2.6

Chu

b M

acke

rel

Spo

tted

Mac

kere

l

Yamada Yamada et al.et al.(1996)(1996)

Insufficient to verify

Sexual maturationSexual maturation(FL & age)(FL & age)

Fork length and age at sexual maturity

The first spawning age was 1 year old.


N:N: 250mm250mmS: 220mmS: 220mm

FL > 300mmFL > 300mm(sample >280mm)(sample >280mm)

FL > 275mmFL > 275mm

FLFL > 310mm> 310mm

Chu

b M

acke

rel

Spo

tted

Mac

kere

l

Ouchi and Hamaski (1979)Ouchi and Hamaski (1979)

Tanoue (1966)Tanoue (1966)

Small Change

Sexual maturationSexual maturation(Temperature)(Temperature)


20.8-24.2 ℃20.8-24.2 ℃

Main: 17-18 Main: 17-18 ℃℃

End: 20-22 ℃End: 20-22 ℃

15-22 ℃15-22 ℃

17-25 ℃17-25 ℃

Chu

b M

acke

rel

Spo

tted

Mac

kere

l

Murata Murata et alet al.(2005).(2005)

Reasonable

Nashida Nashida et al.et al.(2006)(2006)

Spawning period Spawning period


S: Jan to FebS: Jan to FebN: Mar to N: Mar to

JunJun

S: Jan to MayS: Jan to May

S: No sampleS: No sampleN:N: Feb to JunFeb to Jun

S: Feb to S: Feb to MayMay

Chu

b M

acke

rel

Spo

tted

Mac

kere

l

Ouchi and Hamaski (1979)Ouchi and Hamaski (1979)

Tanoue Tanoue et al.et al.(1960)(1960)

Sample too smallLarve: Feb and MarOzawa (1984)Ozawa (1984)

Spawning groundSpawning groundPrevious 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)

Agree with Kijima (1986)

Future studiesFuture studies

V.S

Differential optimal temperatures for

growth rates during the early life stage

Takasuka et al.(2007)

Changes of suitable areas for spawning

Sakurai et al.(2000)

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 mackerelthe relationships between SST and growth rates

during the early life stages of chub and spotted mackerel may be focused on.

Expansion

Reduction

spawning success

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 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.

In the futureIn the future

Fishingactivities

Spawningground

SST

Stocksize

吳欣蓓

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