the ecosystem of tsushima warm current in the japan/east ... · 1 pices/globec symposium on climate...

1

PICES/GLOBEC Symposium on Climate variability and ecosystem impacts on the North Pacific: A basin-scale synthesis

Honolulu, Apr.19-21, 2006

The late-1980s regime shift in the ecosystem of Tsushima

Warm Current in the Japan/East Sea: evidence of historical data

and possible mechanismsYongjun Tian, Hideaki Kidokoro, Tatsuro Watanabe

and Naoki IguchiJapan Sea National Fisheries Research Institute,

Fisheries Research Agency, 　　　NIIGATA, JAPAN

2

Outlines of This Study1. Background and objectives2. Data and methods3. Late 1980s oceanic regime shift in TWC4. Changes in plankton biomass 5. Variation patterns in fisheries production:

analysis of fisheries statistics data (1964-2004)6. Spatial-temporal variability in demersal fish

assemblages: analysis of “Offshore Trawl Data (1974-2004)”

7. Summary and mechanisms of the late 1980s ecological regime shift in TWC

3

30

35

40

45

50

125 130 135 140 145

JAPAN

RUSSIA

KOREA

TC

LC

PF

200m

200m

200mSubtropical CirculationENSO-scale？

Subarctic CirculationDecadal Scale ?

Aleutian Low

ENSO

Asian Monsoon

Warm Water Species

Tunas, yellow tail, Jack mackerel, common squid, etc.

Cold Water Species

Atka mackerel, walleye pollock, Pacific cod, etc.

4

TWO OBJECTIVES1. To identify the regime shift in the ecosystem of TWC: from low trophiclevel plankton to fish community

2. To unravel the mechanisms whereby climatic and oceanic variability are linked to the ecosystem regime shift in TWC in late 1980s.

5

Data and Methods1. Catch statistics: 1964-2004:

54 species items, 90% of total catches2. Japan Sea Offshore Trawl Data Set

1974-2004: 27 demersal species, catches and CPUE with spatial resolution of 10 minutes

4. Oceanographic-climatic indicesSST: 1°×１°grid data set from JMA, 1950-2004 50 to 200 m depth WT: 1964- 2004:

an indicator of Tsushima Warm Current 5. PCA Analysis and GIS Approach

3. Plankton data set: PM Line 1972-2004

6

Indicator of Tsushima Warm Current

50 m depth water temperature (winter)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

1964 1969 1974 1979 1984 1989 1994 1999 2004

Ano

mal

ies （℃

）

Anomalies (winter)regime mean

Late 1980s

7

Spatial differences in winter SSTs46°N

44°N

42°N

40°N

38°N

36°N

34°N

32°N

30°N

124°E 126°E 128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E 144°E 146°E

0 500km250

1970-79(WIN)

-5.5 - -1.5

-1.5 - -1

-1 - -0.5

-0.5 - 0

0 - 0.5

0.5 - 1

1 - 2.5

46°N

44°N

42°N

40°N

38°N

36°N

34°N

32°N

30°N

124°E 126°E 128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E 144°E 146°E

0 500km250

1980-89(WIN)

-5.5 - -1.5

-1.5 - -1

-1 - -0.5

-0.5 - 0

0 - 0.5

0.5 - 1

1 - 2.5

46°N

44°N

42°N

40°N

38°N

36°N

34°N

32°N

30°N

124°E 126°E 128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E 144°E 146°E

0 500km250

1990-99(WIN)

-5.5 - -1.5

-1.5 - -1

-1 - -0.5

-0.5 - 0

0 - 0.5

0.5 - 1

1 - 2.5

46°N

44°N

42°N

40°N

38°N

36°N

34°N

32°N

30°N

124°E 126°E 128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E 144°E 146°E

0 500km250

2000-05(WIN)

-5.5 - -1.5

-1.5 - -1

-1 - -0.5

-0.5 - 0

0 - 0.5

0.5 - 1

1 - 2.5

1970s

1980s

1990s

2000s

46°N

44°N

42°N

40°N

38°N

36°N

34°N

32°N

30°N

124°E 126°E 128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E 144°E 146°E

0 500km250

DIFF.(WIN)

-5.5 - -1.5

-1.5 - -1

-1 - -0.5

-0.5 - 0

0 - 0.5

0.5 - 1

1 - 2.5

Regime difference:

mean of 1987-2004-

mean 0f 1976-86

Decadal mean - 30 years (1970-1999) mean

8

spring50m

Spatial differences (1990s-1980s) in WT100m

spring

fall fallNote

1980s :

1982-1988

1990s:

1989-1995

9

１３２－１３３Ｅ１３３－１３４Ｅ

１３６－１３７Ｅ１３９－１４０Ｅ

1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000

1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000

0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

101- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

1- 3月4- 6月7- 9月10-12月

Yearly changes in 200m depth water temperature by longitude and season

WinterSpring

SummerAutumn

WinterSpring

SummerAutumn

Northern Region

Southern RegionMid-1970s global regime shift is not evident

Late-1980s oceanic regime shift is evident:

it occurred not only in the surface Tsushima warm water, but also in deep water.

10

With 1976/77 regime shift

strength of Aleutian Low

PDO positive

El Nino trend

But the late-1980s

regime shift is not

evident

Climate Indices(a) NPI

-9

-6

-3

0

3

6

9

1950 1960 1970 1980 1990 2000Year

Win

ter

NPI

(hPa

)

-10

0

10

20

30

40

50

CuS

um (h

Pa)

(b) PDO

-3

-2

-1

0

1

2

3

1950 1960 1970 1980 1990 2000Year

Win

ter

PDO

-20

-15

-10

-5

0

5

CuS

um

(c) SOI

-3

-2

-1

0

1

2

3

1950 1960 1970 1980 1990 2000Year

SOI

-3

0

3

6

9

CuS

um

NPI

PDO

SOI

1976/77

With late 1980s regime

shift

AOI positive

Weakenessof Asian monsoon

→

Increase of water

temperature?

1987/88(d) AO

-3

-2

-1

0

1

2

3

1950 1960 1970 1980 1990 2000Year

-20

-15

-10

-5

0

5

CuS

um

Win

ter

AO

(e) MOI

0

3

6

9

1950 1960 1970 1980 1990 2000Year

-10

0

10

20

30

CuS

um (h

Pa)

AOI

MOI

-9

-6

-3

Win

ter

MO

I (hP

a)

11

Phytoplankton (Diatom) : 1972-2004Diatom: spring

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Ano

mal

ies (

Log

10

(cel

l/l +

1)

Diatom: summer

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Ano

mal

ies (

Log

10

cell/

l +1)

Late 1980s

30

35

40

45

50

125 130 135 140 145

PM LineStn.4,5,6

Decadal variability and abrupt change around late 1980s

Different pattern in spring and summer reflecting different

species composition ?

12

Zooplankton (Wet weight): 1972-2004zooplankton: winter

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Bio

mas

s ano

mal

ies (

mg/

m3)

Zooplankton: spring

-60

-40

-20

0

20

40

60

80

100

120

140

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Bio

mas

s ano

mal

ies (

mg/

m3)

Late 1980s

Zooplankton: summer

-30

-20

-10

0

10

20

30

40

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Bio

mas

s ano

mal

ies (

mg/

m3)

Zooplankton: autumn

-40

-30

-20

-10

0

10

20

30

1972 1976 1980 1984 1988 1992 1996 2000 2004

Year

Bio

mas

s ano

mal

ies (

mg/

m3)

Late 1980s

Large interannual and decadal variation: high (lower)during 1990s (1980s) except in winter

13

Catches Trend in the Japan Sea during 1964-2004

0

500

1000

1500

2000

1964 1969 1974 1979 1984 1989 1994 1999 2004

Year

Cat

ch (t

hous

and

met

ric

tons

)

piscivores

pelagic species

sardine

demersal fishes

invertebrates

sardinesmall pelagics

demersal

12

15

14

13

54

26 warm water (pelagic ) species

28 cold water (demersal) species

0%

20%

40%

60%

80%

100%

1964 1969 1974 1979 1984 1989 1994 1999 2004

Year

Prop

ortio

n of

Cat

ch

piscivores

pelagic species

demersal fishes

invertebrates

small pelagics(excluding saridine)

demersal

piscivores

invertebrates

14

PC1=53.0%

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1964 1969 1974 1979 1984 1989 1994 1999 2004

PC2=16.1%

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1964 1969 1974 1979 1984 1989 1994 1999 2004

PC3=6.7%

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

1964 1969 1974 1979 1984 1989 1994 1999 2004

PCAs of 54 species items: 1964-2004PC1=28.3%

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1964 1969 1974 1979 1984 1989 1994 1999 2004

PC2=22.1%

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

1964 1969 1974 1979 1984 1989 1994 1999 2004

PC3=13.2%

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1964 1969 1974 1979 1984 1989 1994 1999 2004

Pelagic (26) species Demersal (28) speciesWarm water 64%<---- PC1-3-- 76% Cold water

Late 1980sLate 1980s

15

Catch Trend of Indicator Species(e ) J a pa ne s e s a rdine

- 4 0 0

- 2 0 0

0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(f) W a lle y e po llo ck

- 1 0 0

- 5 0

0

5 0

1 0 0

1 5 0

2 0 0

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(g ) C ra bs

- 3 0

- 2 0

- 1 0

0

1 0

2 0

3 0

4 0

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(g ) P ink s hrim p

-2

-1

0

1

2

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(a ) T una

- 6

- 4

- 2

0

2

4

6

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(b) Ye llo wta il

- 1 5

- 1 0

- 5

0

5

1 0

1 5

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(c ) H o rs e m a ck e re l

- 7 5

- 5 0

- 2 5

0

2 5

5 0

7 5

1 0 0

1 2 5

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

(d) C o m m o n s quid

- 2 0 0

- 1 5 0

- 1 0 0

- 5 0

0

5 0

1 0 0

1 5 0

2 0 0

1 9 6 4 1 9 6 9 1 9 7 4 1 9 7 9 1 9 8 4 1 9 8 9 1 9 9 4 1 9 9 9 2 0 0 4

Cat

ch a

nom

alie

s (th

ousa

nd to

ns)

Large fishes

warm water

migratory

Species

Small pelagic

species

cold water

or

deep water

demersal

species

16

Community indices from 54 species Mean Trophic Level and Simpson’s Diversity Index

Mean Trophic Level

2.6

2.8

3.0

3.2

3.4

3.6

1964 1969 1974 1979 1984 1989 1994 1999 2004Year

Mea

n tr

ophi

c le

vel

NorthernSouthern

Biomass Diversity Index

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1964 1969 1974 1979 1984 1989 1994 1999 2004Year

Div

ersit

y in

dex

Northern

Southern

Decadal scale

changes

Decreased during Mid-1970s-1980s

but increased

during 1990s

17

Offshore Bottom Trawl : Target speciesNo Japanese Name Scientific Name English Name Depth (m)Life span (years) Current

1 マダラ Gadus macrocephalus Pacific cod 200-300 >12 CW2 スケトウダラ Theragra chalcogramma Walleye pollock 100-500 >11 CW3 ホッケ Pleurogrammus azonus Arabesque greenling <200 >8 CW4 ハタハタ Arctoscopus japonicus Japanese sandfish 300-500 5 CW5 サメ・エイ　（アブラSqualus acanthias Piked dogfish 150-180 >10 CW6 ハツメ Esbastes owstoni Owenton's rockfish 190-300 >10 CW7 ヒレグロ Glyptocephalus stelleri witch flounder 200-300 >12 CW8 アカガレイ Hippoglossoides dubius flathead flounder 150-500 >10 CW9 マガレイ Pleuronectes herzensteini brown sole 30-130 >10 CW

10 その他のカレイ Pleuronectidae other righteye flounder CW11 ホッコクアカエビ Pandalus borealis Pink shrimp 200-600 11 CW12 ズワイガニ Chionoecetes opilio Tanner crab 200-500 >10 CW13 ソウハチ Hippoglossoides pinetorum pointhead flounder 150-190 8 WW14 ムシガレイ Eopsetta grigorjewi shotted halibut <140 >10 WW15 ヤナギムシガレイ Tanakius kitaharai willowy flounder 80-150 >10 WW16 ニギス Glossanodon semifasciatus Deepsea smelt <200 5 WW17 ヒラメ Paralichthys olivaceus bastard halibut <150 >10 WW18 マダイ Pagrus major Silver seabream <100 >10 WW19 チダイ Evynnis japonica crimson seabream 30-130 >6 WW20 キダイ Dentex tumifrons deepsea snapper <200 >8 WW21 エソ Synodontidae Lizardfish <120 <4 WW22 グチ (シログチ） Sciaenidae (Argyrosomus a Croaker 20-120 6? WW23 カナガシラ Lepidotrigla micropetera redwing searobin 70-140 6 WW24 タチウオ Trichiurus japonicus Largehead hairtail 20-140 8 WW25 アカムツ Doederleinia berycoides blackthroat seaperch 80-150 10 (Female) WW26 イカ類 Squids <200 <2 WW27 タコ類 Octopus <200 WW

Total 27 speices items

12 cold water species:

Deep water

Long-lived

Northern distribution

15 warm water species:

Coastal and continental shelf

Short-lived

Southern

distribution

CW: Cold Water WW: Warm Water Nishimura (1969)

18

Offshore Bottom Trawl : Catch and CPUE

EFFORT

0

50000

100000

150000

200000

250000

300000

350000

400000

1974 1979 1984 1989 1994 1999 2004

Year

Num

ber

of h

auls

OffshoreNortheasternCentralSouthwestern

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E

0 200km100

Central

Southwestern

NortheasternOffshore

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E

0 200km100

Central

Southwestern


Central

Southwestern


Catch

0

10

20

30

40

50

1974 1979 1984 1989 1994 1999 2004

Year

Cat

ch　

(thou

sand

tons

)

OffshoreNortheasternCentralSouthwestern

ＣＰＵＥ

0

50

100

150

200

250

300

350

1974 1979 1984 1989 1994 1999 2004

Year

CPU

E (k

g/ha

ul)

NortheasternCentralSouthwesternOffshore

19

Changes in compositions

Northeastern

0%

20%

40%

60%

80%

100%

1974 1979 1984 1989 1994 1999 2004

Year

Prop

ortio

n

Warm

Cold

Offshore

0%

20%

40%

60%

80%

100%

1974 1979 1984 1989 1994 1999 2004

Year

Prop

ortio

n

Warm

Cold

Central

0%

20%

40%

60%

80%

100%

1974 1979 1984 1989 1994 1999 2004

Year

Prop

ortio

n

Warm

Cold

Southwestern

0%

20%

40%

60%

80%

100%

1974 1979 1984 1989 1994 1999 2004

Year

Prop

ortio

nWarm

Cold

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E

0 200km100

Central

Southwestern


42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E 142°E

0 200km100

Central

Southwestern


Central

Southwestern


20

P C 1 = 3 6 .6 %

-1.5-1.0-0.50.00.51.01.52.02.5

1974 1979 1984 1989 1994 1999 2004

P C 2= 17.3%

-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.5

1974 1979 1984 1989 1994 1999 2004

P C 3= 11.3%

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

1974 1979 1984 1989 1994 1999 2004

PCAs of demersal species from offshore trawl fisheries data during 1974-2004

PC1: changed

around late 1980s

PC1-3: 65% of total

variance

21

CPUE for four cold water indicator species

Cold Warm Cold Warm

Pacific cod

0

5

10

15

20

25

30

1974 1979 1984 1989 1994 1999 2004

CPU

E

0.0

0.5

1.0

1.5

2.0

2.5

CPU

E（Southw

estern）

NortheasternCentralSouthwestern

Wallaye pollock

0

10

20

30

40

50

60

1974 1979 1984 1989 1994 1999 2004

CPU

E

0

2

4

6

8

10

12

14

CPU

E（

Southwestern）


Witch flounder

0

1

2

3

1974 1979 1984 1989 1994 1999 2004

CPU

E

0

5

10

15

CPU

E（

Southwestern）


Flathead flounder

0

5

10

15

20

25

1974 1979 1984 1989 1994 1999 2004

CPU

E

0

5

10

15

20

25

30

35

40

CPU

E（

Southwestern）


During warm regime, CPUE of the these cold water species in

the southwestern region is decreased; while CPUE in the

northern regions maintained in a relative high level: indicating

a reduction of southwestern distribution

22

CPUE for four warm water indicator species

Redwing searobin

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1974 1979 1984 1989 1994 1999 2004

CPU

E

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

CPU

E（

Southwestern）


Cold WarmCold Warm Cold WarmCold Warm

Pointhead flounder

0.0

0.5

1.0

1.5

2.0

1974 1979 1984 1989 1994 1999 2004

CPU

E

0

5

10

15

20

25

CPU

E（

Southwestern）


Willowy flounder

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1974 1979 1984 1989 1994 1999 2004

CPU

E

0.00

0.02

0.04

0.06

0.08

CPU

E（Southw

estern）


Deepsea snapper

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1974 1979 1984 1989 1994 1999 2004

CPU

E

0.00

0.05

0.10

0.15

0.20

CPU

E（Southw

estern）


During warm regime, CPUE of the these warm water species

largely increased not only in the southwestern region but also in the northern regions: indicating

northward expansion of distribution and increase in

abundance level

23

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1980-84)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 5330

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1995-99)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 5330

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1995-99)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 710

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1980-84)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 710

Pacific cod

1990s

warm

Walleye pollock

Cold regimeIncrease in abundance

(Expansion of distribution)

Warm regimeDecrease in abundance

(Reduction of distribution)

Cold water species

1980s

cold

24

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1995-99)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 910

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1995-99)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 770

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1980-84)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 770

42°N

41°N

40°N

39°N

38°N

37°N

36°N

35°N

34°N

128°E 130°E 132°E 134°E 136°E 138°E 140°E

CPUE(1980-84)

0 - 1

1 - 50

50 - 100

100 - 150

150 - 200

200 - 250

250 - 910

1990s

warm

Warm water speciesPointhead flounder

Cold water speciesWitch flounder

1980s

cold

25

Response process to late 1980s regime shift in TWC

Intensification of Aleutian Low and Asian monsoon

cold 1980s warm 1990s

Weakeness of Asian monsoonAOI positive

Cold water temperature

phytoplankton

zooplankton

Warm water temperature

Cold water species Demersal, habitat

(Winter-spring)

Warm water species Pelagic, migratory (Summer-autumn)

Warm water species Pelagic, migratory (Summer-autumn)

Cold water species Demersal, habitat

(Winter-spring) positive

negativepositive

negative

26

Summary and Conclusions1. An oceanic regime shift from cold to warm water is

identified in TWC region in late-1980s and linked with global climatic changes.

2. Plankton biomass changed abruptly around late 1980s with decadal variability.

3. PCA and community indices suggested that the fish community in TWC changed around late 1980s.

4. Both the pelagic and demersal fish assemblages show decadal variation patterns and changed around late 1980s.

5. Response patterns are different between cold and warmwater species: warm (cold) water species increased(decreased) their abundances and expanded (reduced) their distributions during the warm regime, and vice versa.

6. These suggested an ecosystem regime shift from low trophic plankton to high trophic fish communities, occurred in TWC in late 1980s, and is linked directly to the climatic-oceanic regime shift in the North Pacific.

the ecosystem of tsushima warm current in the japan/east ... · 1 pices/globec symposium on climate...

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