. Title PICES/GLOBEC Symposium, T3-2672 Why were anchovy and sardine regime shifts synchronous across the Pacific? Akinori Takasuka 1, Yoshioki Oozeki 1, Hiroshi Kubota 1, Ichiro Aoki 2 1 National Research Institute of Fisheries Science, Fisheries Research Agency 2 Graduate School of Agricultural and Life Sciences, University of Tokyo PICES/GLOBEC Symposium on Climate Variability and Ecosystem Impacts on the North Pacific: A Basin-Scale Synthesis (Theme 3: Pan-Pacific comparisons, ) Ala Moana Hotel, Honolulu, Friday, April 21, 26
Fish regime shift et al. Introduction 1 Climate changes and fish regime shifts Small pelagic fish have repeatedly shown cyclic population dynamics in the complex marine ecosystems worldwide. Fish regime shifts have been attributed to climate changes. However, the biological processes have remained unclear. PDO Catch (1 5 t) Anchovy, Jack mackerel 2 1-1 -2 6 5 4 3 2 1 Jack mackerel Anchovy 19 192 194 196 198 2 Year Mackerel 6 5 4 3 2 1 Multi-species fish regime shifts in response to Pacific Decadal Oscillation (PDO) (Mantua et al. 1997) in the western North Pacific., Mackerel Synchronous anchovy and sardine alternations despite the reversed temperature regimes across the Pacific (Chavez et al. 23).
Questions et al. Introduction Preliminary question Why do even subtle environmental changes sometimes trigger drastic fish regime shifts? Key question Why do anchovy flourish and sardine collapse or vice versa under the same ocean regime? Target question Why were anchovy and sardine regime shifts synchronous across the Pacific? Extended question Why do some species show synchronous patterns, while others show out-of of-phase patterns? We explored the simplest and most direct pathway to address the biological processes of fish regime shifts
Topic 1 et al. Introduction Differential optimal temperatures for growth rates during early stages between anchovy and sardine Preliminary question Why do even subtle environmental changes sometimes trigger drastic fish regime shifts? Key question Why do anchovy flourish and sardine collapse or vice versa under the same ocean regime?
Growth survival et al. Introduction 4 Growth survival paradigm during early life stages Growth mortality hypothesis (Anderson 1988) Faster growing larvae are more likely to survive in the sea. Three growth-related related mechanisms Bigger is better hypothesis (Miller et al. 1988) Size: negative size-selective mortality Stage duration hypothesis (Chambers & Leggett 1987, Houde 1987) Time: high mortality larval stage duration Growth-selective predation hypothesis (. 23, 24) Growth rate (per se): direct impacts on vulnerability to predation In theory, In theory, These are independent of and synergistic with one another. Even subtle variations in growth rates potentially cause drastic fluctuations in survival probability and recruitment.
Objectives et al. Introduction 5 Relationships between growth rates during early stages and sea temperature were examined for Japanese anchovy and sardine. Engraulis japonicus VS. Sardinops melanostictus Optimal growth temperature hypothesis: A potential biological mechanism for anchovy and sardine regime shifts?
Samples et al. M & M 2 Latitude 5 45 4 35 At 5 stations during 199 24 Western North Pacific Kuroshio Extension region Larval anchovy All seasons 34 samples 241 larvae 6 35 mm SL Larval sardine 3 25 125 13 135 14 145 15 155 16 Longitude Jan. Jun. 3 samples 766 larvae 8 35 mm SL Sampling areas and stations for Japanese anchovy and sardine larvae in the western North Pacific.
Anchovy vs. et al. Results 2 Growth rate (mm day 1 ) 1.2 1..8.6.4.2 Anchovy 1 15 2 25 Sea surface temperature ( C) Relationship between recent 3-day mean growth rates and sea surface temperature for larval anchovy and sardine.
Anchovy vs. et al. Results 3 Growth rate (mm day 1 ) 1..8.6.4.2 Anchovy 16.2ºC 22.ºC 1 15 2 25 Sea surface temperature ( C) Relationship between recent 3-day mean growth rates and sea surface temperature for larval anchovy and sardine.
Mechanism et al. Results 4 Growth rate (mm day 1 ) 1..8.6.4.2 Anchovy collapse flourish Anchovy Temperature shift Anchovy flourish collapse 1 15 2 25 Sea surface temperature ( C) Conceptual framework of a potential mechanism for fish regime shifts based on the differential optimal growth temperatures.
Ambient temperature et al. M & M 3 What temperatures are they likely to experience? Is the difference in optimums really significant? Spawning ground Assumption: Sea surface temperatures (SSTs) in the spawning regulate larval growth rates after hatching. Egg-density density-weighted mean SSTs for anchovy and sardine Latitude 45 4 35 3 25 125 13 135 14 145 15 Longitude Egg and larval surveys Anchovy eggs eggs Off the Pacific coast From 1978 to 24 All seasons All stations Annual mean
Time series data et al. Results 5 Temperature ( C) Growth rate (mm day 1 ) ln RPS 24 22 Anchovy 2 18 16 14 1975 198 1985 199 1995 2 25.6.5.4.3 1975 198 1985 199 1995 2 25 8 6 4 2 Egg-density-weighted mean SST Growth rate converted from SST Recruitment per spawning biomass (RPS) as a larval survival index Biomass (1 6 t) Anchovy 1975 198 1985 199 1995 2 25 2 2 Anchov y 15 1 1 5 1975 198 1985 199 1995 2 25 Biomass Year Retrospective test with the times series data of egg-density density-weighted mean SST, growth rate, survival index, and biomass for anchovy and sardine.
. Hypothesis proposed Conclusions Optimal growth temperature hypothesis Potential biological mechanism for fish regime shifts The theory is independent of and synergistic with the existing hypotheses. Optimal temperature would provide a necessary condition rather than a sufficient condition. I. Growth survival paradigm II. Direct temperature impacts III. Differential optimal growth temperatures
. Topic 2 Question Contrastive spawning temperature optimums of anchovy and sardine between the opposite sides of the Pacific Target question Why were anchovy and sardine regime shifts synchronous across the Pacific? (despite the reversed temperature regimes)
. Chavez et al.. (23) Introduction Hypothetical oscillation of a regime index with a period of 5 years (Chavez et al. 23).
. East West paradox Introduction Not a few researchers consider that temperature should not be the dominant and direct factor. If temperature is the dominant factor, the phenomenon is strange as it means that anchovy (or sardine) respond to temperature differently among regions However, We believe that temperature-related parameters of anchovy and sardine are quite different between the opposite sides of the Pacific. To confirm this,
. Objectives Introduction Why were anchovy and sardine regimes synchronous across the Pacific? A preliminary step toward basin-scale synthesis Spawning temperature optimums were compared between Japanese anchovy and sardine in the western North Pacific. The results were compared with those in the California Current by Lluch-Belda et al. (1991). Western Boundary Current system vs. Upwelling system
Data et al. M & M 1 Long-term dataset of the historical egg and larval surveys Off the Pacific coast of Japan Past 27 years (1978 24) 12,95 tows Over 3, tows per year Sampling stations of the historical egg and larval surveys off the Pacific coast of Japan from 1978 to 24.
Frequency The methods of Lluch-Belda et al. (1991) et al. Results 1 (1) All tows were classified into SST intervals of.1ºc. (2) All tows were sorted for positive tows for anchovy and sardine eggs and larvae. Frequency 12 1 8 6 4 2 5 1 15 2 25 3 35 All tows Anchovy eggs Anchovy larvae eggs larvae Sea surface temperature ( C) Frequency distributions of plankton net tows (stations) classified into the sea surface temperature intervals of.1ºc.
Relative frequency et al. Results 2 (3) Spawning temperature index was calculated as ratio of relative frequencies of positive tows vs. all tows for each SST interval. (4) Assumption: The value of index > 1.: Preferred or selected 2.5 All tows 2. Anchovy eggs Anchovy larvae eggs 1.5 larvae Relative frequency (%) 1..5 The methods of Lluch-Belda et al. (1991) 5 1 15 2 25 3 35 Sea surface temperature ( C) Relative frequency distributions of plankton net tows (stations) classified into the sea surface temperature intervals of.1ºc.
Western North Pacific et al. Results 3-1 Spawning temperature index (11-term running mean) 3. 2.5 2. 1.5 1..5. 5 1 15 2 25 3 E. japonicus eggs E. japonicus larvae Sea surface temperature ( C) Spawning temperature index for Japanese anchovy (E. japonicus) in the western North Pacific.
Western North Pacific et al. Results 3-2 Spawning temperature index (11-term running mean) 3. 2.5 2. 1.5 1..5. 5 1 15 2 25 3 Sea surface temperature ( C) S. melanostictus eggs S. melanostictus larvae Spawning temperature index for Japanese sardine (S. melanostictus) in the western North Pacific.
Western North Pacific et al. Results 3-3 Spawning temperature index (11-term running mean) 3. 2.5 2. 1.5 1..5. OGT = 16.2ºC 22.ºC = OGT WEST 5 1 15 2 25 3 E. japonicus eggs E. japonicus larvae S. melanostictus eggs S. melanostictus larvae Sea surface temperature ( C) Spawning temperature index for Japanese anchovy (E. japonicus) and sardine (S. melanostictus) in the western North Pacific.
Spawning temperature index (11-term running mean) East West et al. Results 3-5 3. 2.5 2. 1.5 1..5. 2. 1.5 1..5. WEST 5 1 15 2 25 3 EAST Lluch-Belda et al. (1991) 5 1 15 2 25 3 Sea surface temperature ( C) E. japonicus eggs E. japonicus larvae S. melanostictus eggs S. melanostictus larvae Western North Pacific (off the Pacific coast of Japan) E. mordax eggs E. mordax larvae S. sagax eggs S. sagax larvae Eastern North Pacific (in the California Current) Contrastive spawning temperature optimums of anchovy and sardine between the opposite sides of the Pacific.
East West et al. Results 4 Spawning temperature index > 1. E. japonicus S. melanostictus E. mordax S. sagax Eggs Larvae Present study Western North Pacific Eastern North Pacific Lluch-Belda et al. (1991) 1 15 2 25 3 Sea surface temperature ( C) Western North Pacific Eastern North Pacific E. japonicus: Warm & Eurythermal S. melanostictus: Cool & Stenothermal VS. E. mordax: Cool & Stenothermal S. sagax: Warm & Eurythermal
. Conclusions Conclusions Western North Pacific Spawning temperature optimums clearly distinguished the warm and eurythermal anchovy and cool and stenothermal sardine in the western North Pacific. Across the Pacific Contrastive spawning temperature optimums of anchovy and sardine between the opposite sides of the Pacific. Possible theoretical solution: Reversed species-specific specific temperature optimums under the reversed temperature regimes would provide a possible theoretical solution to the synchronous fish regime shifts across the Pacific.
Topic 3 et al. Introduction 1 Multi-species fish regime shifts reflected in spawning temperature optimums in the western North Pacific PDO Catch (1 5 t) Anchovy, Jack mackerel 2 1-1 -2 6 5 4 3 2 1 Jack mackerel Anchovy 19 192 194 196 198 2 Year Mackerel 6 5 4 3 2 1, Mackerel Extended question Why do some species show out-of of-phase patterns, while others show synchronous patterns?
Multi-species comparison et al. Results 5 Catch (1 5 t) Anchovy, Jack mackerel 6 5 4 3 2 1 Jack mackerel Anchovy Mackerel 19 192 194 196 198 2 Year 3. 6 5 4 3 2 1, Mackerel Anchovy Spawning temperature index (11-term running mean) 2.5 2. 1.5 1..5 Mackerel Jack mackerel Anchovy Mackerel Jack mackerel. 5 1 15 2 25 3 Sea surface temperature ( C) Similarities and differences in spawning temperature patterns represent those in the long-term population dynamics patterns.
. Implications Implications TOO SIMPLE? Synergistic mechanisms No single factor is enough to explain fish population dynamics. There should be synergistic effects of the other factors. Despite the complex nature, Temperature-based hypotheses The dominant mechanism of the large-scale events may be simple and direct. Species-specific temperature optimum ideas could at least theoretically address what has been hard to explain by the other factors. Direct temperature impacts on fish population dynamics might be greater at the large scales than expected before.
. Thank you for your precious time. Finish ALPI Anchovy ( 1 5 t) Growth rate (mm day 1 ) Growth rate (mm day 1 ) 4-2 2-4 6 6 5 Anchovy 5 4 4 3 3 2 2 1 1 19 192 194 196 198 2 Year Anchovy and sardine regime shifts 1..8.6.4.2 Anchovy 1 15 2 25 1..8.6.4.2 Anchovy Sea surface temperature ( C) 1 15 2 25 Sea surface temperature ( C) Optimal growth temperature hypothesis ( 1 5 t) Spawning temperature index (11-term running mean) 3. 2.5 2. 1.5 1..5. 2. 1.5 1..5. Catch (1 5 t) Anchovy, Jack mackerel Spawning temperature index (11-term running mean) WEST 5 1 15 2 25 3 EAST Lluch-Belda et al. (1991) 5 1 15 2 25 3 Sea surface temperature ( C) E. japonicus eggs E. japonicus larvae S. melanostictus eggs S. melanostictus larvae E. mordax eggs E. mordax larvae S. sagax eggs S. sagax larvae Contrastive spawning temperatures 6 5 4 3 2 1 Jack mackerel Anchovy 19 192 194 196 198 2 3. 2.5 2. 1.5 1..5. Year Mackerel Mackerel 5 1 15 2 25 3 Sea surface temperature ( C) Multi-species comparison 6 5 4 3 2 1 Jack mackerel Anchovy, Mackerel