Distribution and Population Dynamics of Japanese Sardine, Anchovy and Chub

Mackerel in the Kuroshio/Oyashio System: Seeking for Mechanistic Responses to

Regime Shifts

Akihiko Yatsu1, Hiroshi Kubota1, Akinori Takasuka1, Motomitsu Takahashi2, Norio Yamashita1, Hiroshi

Nishida1, Chikako Watanabe1, and Yoshioki Oozeki1

1 National Research Institute of Fisheries Science, Japan2 Integrative Oceanography Division, Scripps Institution of Oceanography, USA

Recent Distribution of Japanese Sardine, Anchovy, Mackerels in the Northwestern Pacific

Sardine (Low Stock) Anchovy (High Stock) Chub mackerel

Distribution

=Feeding gr.

Spawning ground

Distribution

Spawning ground

Feeding ground

Distribution

=Feeding ground

=Spawning ground

3 species share common feeding ground and to some extent spawning ground

Anchovy spawning and feeding grounds are overlapping

Japanese Catch of Japanese Sardine, Anchovy, Mackerels during 1905-2001

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

1905 1915 1925 1935 1945 1955 1965 1975 1985 1995

Cat

ch in

ton

(Sar

dine

)

0

500,000

1,000,000

1,500,000

2,000,000

Cat

ch in

ton

(Anc

hovy

,　M

acke

rels

)SardineAnc hovyMac ke re lsRe g ime s hift

Mackerels: chub mackerel + spotted mackerel

Regime shift years: after Yasunaka and Hanawa (2002) excl. 1998/99

Alternation of 3 species in a decadal scale is probably related to climatic regime shifts

Locations of Spawning Ground of Japanese

Sardine during1960s-90sEstimatedfrom the

Egg CensusSurvey

(Hiramoto, 1996)

Expand beyond Kuroshio during high stock period, but not to KOTZ

Kuroshio

Egg Distribution of Japanese Anchovy (Zenitani and Kimura, 1997)

Expand to KOTZ during high stock period, but not south of Kuroshio

Kuroshio

KOTZ

Driftnet CPUE at 155E during June, 1976-1999, by Hokkaido University

マイワシ

32.5

35.0

37.5

40.0

42.5

45.0

75 80 85 90 95 100

Year

緯度

(N

)

= 5000

= 1000= 200= 50

カタクチイワシ

32.5

35.0

37.5

40.0

42.5

45.0

75 80 85 90 95 100

西暦

緯度

(N

)

= 5000

= 1000= 200= 50

マサバ

32.5

35.0

37.5

40.0

42.5

45.0

75 80 85 90 95 100

西暦

緯度

(N

)

= 5000

= 1000= 200= 50

Sardine

Anchovy

Chub mackerel

Year (1900+)

Year (1900+)

Latit

ude

(N)

Latit

ude

(N)

Latit

ude

(N)

Driftnet monitoring sites at 155E

Adult distribution expand to open ocean

during high stock period, in the 3 species

Basic Biology Japanese sardine Japanese anchovy Chub mackerel

　 　 　

Life span about 7 yr about 3 yr 7 yr or moreMax size BL 25 cm 14 cm 40 cm

　 　 　

Fist maturity age(year)

1 (Low Stock) or3 (High Stock) 1 2 (Low Stock) or

3 (High Stock)　 　 　

Fist maturity BL 17 cm 6 cm 30 cm　 　 　

Spawning season winter spring-autumn spring

Spawning area

southern Honshu -Kyushu

(expand to open ocean beyond Kuroshio in the

High Stock period )

northern Honshu -Kyushu

(expand to open ocean in KOTZ in the High

Stock period)

central Honshu - Kyushu

　 　 　

Prey

phytoplankton (Diatom) and zooplankton

(Calanus, Oncaea, Corycaeus,

Paracalanus)

zooplankton (Oncaea, Microsetella,

Corycaeus, Eucalanus, Paracalanus, Oithona)

zooplankton (Neocalanus, Eucalanus, Krill),

anchovy, squid, salps

Correlation Coefficient (r) Map between Winter SSTand LNRR of Japanese Sardine (Yatsu et al., 2005)

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

0 5000 10000 15000

SSB (1000t)

Recru

itm

ent

(10^6

) 80

86

77

88

LNRR=

ln (Recruitment Residuals)

Ricker curve

●: positive r

○: negative r

KESA

36

38

40

42

-4 -2 0 2 4

PDO

OYSL

OYSL: Oyashio (1st br.) Southern Limit

Correlation Coefficient (r) Map between Winter SSTand LNRR of Chub Mackerel (Yatsu et al., 2005)

0

5,000

10,000

15,000

20,000

25,000

0 1,000 2,000 3,000 4,000

SSB (1000t)

Recru

itm

ent

(mill

ion)

64

67

71

79

63

77

85

69

66

Chub mackerel

LNRR=

ln (Recruitment Residuals)

Ricker curve

●: positive r

○: negative r

Principal spawning grounds

KOTZ: Key Area for Recruitment

Early survival is mainly determined after the feeding larvae distributing in KOTZ

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

78 80 82 84 86 88 90

Year class

Popu

lation n

um

bers

Egg

Yolk-saclarvae

Feedinglarvae

Recruit

Watanabe et al. (1995)

0

20

40

60

80

100

120

140

1996 1998 2000 2002 2004

Recr

uitm

ent

(10 m

illio

n)

0

1

10

100

1,000

Pre

-re

cru

itm

ent

Ind

exRecruitment

Index

KOTZ

Sardine

Sardine

0

10

20

30

40

50

1996 1998 2000 2002 2004

Rec

ruitm

ent

(10 m

illio

n)

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

Pre

-re

crui

tmen

t In

dexRecruitment

Index

Chub mackerel

Cladocera75% 76%

Sardine Anchovy

N=12, SL=30.4-47.5mm N=5, SL=32.2-40.7mm

Calanus spp.

Corycaeusspp.

Paracalanus spp.

Small Calanoida(PL < 1mm)

Phytoplankton

Oncaeaspp.

Unidentified plankton

Other large copepod

Other small copepod

4.9%

8.1%6.2%

7.6%

5.0%3.0%

2.6%

Oncaeaspp.

Large Calanoida(PL < 1mm)Large

Calanoida(PL < 1mm)

Prey Composition (in No.) of Juvenile Sardine and

Anchovy in KOTZ (May, 1997; Kubota et al., unpublished)

Cladocera and some copepods were common prey

Growth Rate Comparison between Simultaneously Collected Sardine (Gms) and Anchovy (Gma) in

KOTZ (Takahashi et al., PICES XIII 2004)

Gm

s(m

m d

-1)

1997

Gma (mm d-1)

1998

1999

2000

2001

2002

( )

Gms = -1.99 Gma + 2.09(n=5, r=0.84, P = 0.078)

0.4

0.6

0.8

1

0.4 0.6 0.8 11.0

1.0

Poor prey

Sardine Anchovy

Direct effect of temperature on early growth and, hence early survival if prey is sufficient in KOTZ

‘Optimal Growth Temperature’ Hypothesis(Takasuka et al., PICES XIII 2004, submitted)

10 15 20 250

0.2

0.4

0.6

0.8

1.0

Sea surface temperature (°C)

Gro

wth

rat

e (m

m d

ay–1

)

AnchovySardineAnchovySardine

10 15 20 250

0.2

0.4

0.6

0.8

1.0

Sea surface temperature (°C)

Gro

wth

rat

e (m

m d

ay–1

)

AnchovySardine Temperature shift

AnchovyAnchovy flourishSardineSardine collapse

AnchovyAnchovy collapseSardineSardine flourish

16.216.2ººCC 22.022.0ººCC

Different optimum SSTs for early growth were detected in sardine and anchovy collected from various areas and years in the NW Pacific, leading to a plausible hypothesis of regime shift

Early Growth of Chub Mackerel in KOTZ and Recruitment-per-Spawners (RPS) during 2003-2005

(Yamashita et al., unpublished)

0

5

10

15

20

1.00 1.25 1.50 1.75

Growth Rate(mm/day)

RPS (Num

ber/

kg)

2004

2005

2003

0

20

40

60

80

100

0 20 40 60Age (day)

Fork

lengt

h (m

m)

2003(n=32)

2004(n=27)

2005(n=77)

(RPS isTentative value)

Early growth may also be a key for survival of juveniles of chub mackerel --- needs more data

Prey Composition of Skipjack Tuna (2004)（Watanabe et al., unpublished）

April-May 2004 June-August 2004 June-August 2004

Kuroshio Kuroshio KOTZ

Num

ber (

%)

Wei

ght (

%)

Fishes

Frequency (%)

FishesFishes

AnchovyAnchovy

Anchovy

Amphipods

AmphipodsAmphipodsSquids

Squids

Misc

Misc

Decapods

SKJ heavily prey upon anchovy larvae and adults in recent years

Skipjack Catch (1968)

http://ss.myg.affrc.go.jp/tnf/news07/kasahara.htm

May

June

Skipjack Recruitment Anomaly in the

Western North Pacific(Inagake et al., 2005, Enyo

News 116)

More arrival of SKJ since the 1980's but anchovy larvae is less vulnerable to SKJ than sardine

and chub mackerel, due to expanded spawning area to

KOTZ

Migration and InteractionSpawningNursery

Winter

Sardine Anchovy Chub mackerel

Spring

Skipjack

WinteringFeeding

• Predation by skipjack (Kuroshio: Winter, KOTZ: Spring)• Predation of anchovy by chub mackerel (Kuroshio & KOTZ: Spring)• Competition for small copepods between sardine and anchovy (KOTZ)• Less vulnerability of anchovy larvae to skipjack (Kuroshio: Winter)

KOTZ

Kuroshio

Ecosystem Connectivity and Regime Shifts(Bakun and Broad (eds) 2002, Climate and Fisheries)

FIGURE 4. Ecosystem Connectivity. Reproductively isolated local populations may be indirectly connected via a shared resource (i.e., “bottom-up

connectivity”) or a shared predator or fishery (i.e.,“top-down connectivity”). Climatic shifts may affect any of these ecosystem levels.

Sardine Anchovy

Summary: Implications of Temperature and Food Web for the 3 Species in KOTZ

Food web Food web • Direct consumption

of anchovy by chub mackerel

• Possible competition for small copepods between sardine and anchovy

• Less vulnerability of anchovy larvae to skipjack

SSTSST• Vertical mixing and strength

Oyashio - bottom-up• Stratification - timing of spring

bloom • ZP species/size compositions• Growth and survival of larvae • Contact to skipjack (and

squids); higher mortality when SST is high - top-down

Unanswered question: Evolution of different life-histories, particularly between sardine and anchovy