Comparison of Synchronous Ecological Regime Shifts in
the Humboldt and Kuroshio Currents
Jürgen Alheit
Baltic Sea Research Institute Warnemünde, Germany
0
1000
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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
10
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s m
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Japanese sardine
Peru-Chile sardine
Catch Records of Japanese and Peru-Chile sardine populations
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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 20000
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Jap
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Ca
liforn
ia s
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s m
etric
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sJapanese sardine
California sardine
Gulf California
Catch Records of Japanese and California sardine populations
Synchronies in catch records (hard data but mixes fishing with environment)
Interdecadal time series at 23.5°Sc) Zb: thin line - reconstructed thermocline(Pizarro and Montecinos, Geophys. Res. Lett., 2004)
Anchovy and Sardine Catches in Humboldt Current
Year1960 1965 1970 1975 1980 1985 1990 1995 2000
103 m
etric
ton
s
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12000
Anchovy
Sardine
ENSO 82/83
ENSO 97/98
ENSO 72/73
1964 1968 1972 1976 1980 1986 1990
Zo
op
lan
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olu
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[m
l m-3
]
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1964 1968 1972 1976 1980 1986 1990
Zo
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lan
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olu
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l m-3
]
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Year1964 1968 1972 1976 1980 1986 1990
Zo
op
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olu
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[m
l m-3
]
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Northern Peru
Central Peru
Southern Peru
Peruvian Zooplankton Volumes 1964 - 1988
1976 1980 1984 1988 1992 1996 2000P
hyto
pla
nkt
on V
olum
e [
ml m
-3]
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0,5
1,0
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2,0
2,5
1976 1980 1984 1988 1992 1996 2000
Phy
top
lan
kton
Vol
ume
[m
l m-3
]
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1,0
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Year1976 1980 1984 1988 1992 1996 2000
Phy
top
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kton
Vol
ume
[m
l m-3
]
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0,5
1,0
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2,0
2,5
0 – 30 miles
30 – 60 miles
> 60 miles
Peruvian Phytoplankton Volumes 1976 - 1999
1960 1965 1970 1975 1980 1985 1990 1995 2000
Per
cent
age
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Year1960 1965 1970 1975 1980 1985 1990 1995 2000
Per
cent
age
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Anchovy
SardineZooplankton
Dynamics of Anchovies, Sardines, and Zooplankton
Observed Biological Changes in Humboldt Current 1968-71
Regime Shift
Plankton
decrease of Peruvianzooplankton after 68
decrease of Chileanzooplankton after 69
shift in relative abundance of larvae of non-fishedmesopelagic species after 69
Anchovy
biomass decrease 69-71
surplus productionrate turns negative after 68
recruitment collapse 71
other Pelagics
increased sardinespawning since 69
increased relativeabundance of sardine and horse mackerel since 70
Alheit and Niquen 2004Progr. Oceanogr. 60
Mechanisms of Regime Shifts in Humboldt Current – Causal Relationships
slackening of trades
reduced upwelling, deepening of thermocline, productivity changes
advection of warm subtropical oceanic water to coast reduction of cool anchovy habitat
negative impacts on trophodynamics of anchovy
changes in prey fields
reduction of large copepods (anchovy food)
increase of smaller copepods (sardine food)
increased predation due to increased overlap with oceanic predators
increased predation on eggs and larvae
increased predation on juveniles and adults by mackerel and horse mackerel
increased cannibalism of eggs and larvae
increased catchability
density-dependent processes
Normalized Japanese Catches
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1960 1965 1970 1975 1980 1985 1990 1995 2000
%
Anchovy
Sardine
Normalized Sardine Catches
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1960 1965 1970 1975 1980 1985 1990 1995 2000
% Humboldt
Kuroshio
Normalized Anchovy Catches
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1960 1965 1970 1975 1980 1985 1990 1995 2000
%
Humboldt
Kuroshio
Shift anchovy-sardine Peru: 1968-1970
Shift thermocline shallow-deep Peru: 1968-1970
Shift anchovy-sardine Japan: 1966-1972
Shift MLD shallow-deep Kuroshio: mid-1960s____________________________________________________
Shift sardine-anchovy Peru: mid-1980s
Shift thermocline deep-shallow Peru 1982-1983
Shift sardine-anchovy Japan: mid-late 1980s
Shift MLD deep-shallow Kuroshio: 1985
Dynamics of mixed layer depth Kuroshio (Yasuda et al., 2000, Prog. Oceanogr. 47)
Conclusions
Decadal-scale climate variability drives regime shifts of anchovy andsardine populations in HC and KC teleconnection ?
Turning points in dynamics of small pelagics correspond to changes in sub-surface processes (late 1960s-1970; mid-1980s)
No strong signals of climate regime shift in mid-70s in dynamics of HC andKC small pelagics
HC anchovy collapse caused by combination of regime shift and overfishing
Single El Niño events are only short-term perturbations for HC anchovy
Major Question:
What drives teleconnection between Humboldt and Kuroshio systems?