the ecosystem of tsushima warm current in the japan/east ... · 1 pices/globec symposium on climate...
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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
132-133E 133-134E
136-137E 139-140E
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
NortheasternOffshore
Central
Southwestern
NortheasternOffshore
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
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
NortheasternOffshore
Central
Southwestern
NortheasternOffshore
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)
NortheasternCentralSouthwestern
Witch flounder
0
1
2
3
1974 1979 1984 1989 1994 1999 2004
CPU
E
0
5
10
15
CPU
E(
Southwestern)
NortheasternCentralSouthwestern
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)
NortheasternCentralSouthwestern
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)
NortheasternCentralSouthwestern
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)
NortheasternCentralSouthwestern
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)
NortheasternCentralSouthwestern
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)
NortheasternCentralSouthwestern
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.