Differential Impacts of Climate Change on Spawning Populations of Atlantic cod in U.S. Waters
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Differential Impacts of Climate Changeon Spawning Populations of Atlantic cod
in U.S. Waters
Lisa Kerr, Steve Cadrin (UMass School for Marine Science & Technology),
Mike Fogarty(NOAA Northeast Fisheries Science Center),
and Jim Churchill(Woods Hole Oceanographic Institution)
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Outline
• History of fisheries oceanography– Oceanographic foundations of
fisheries science– Single-species demographic
conventions– Recruitment studies– Incorporating environmental factors in
fishery stock assessment– An emerging role for simulation
• Case study: cod and climate off New England.
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Formative Years of Fisheries Oceanography• Northeast Atlantic:
– ICES was formed in 1902 primarily to explain fluctuations in fishery yields, and adopted an oceanographic approach to studying fisheries.
• Northwest Atlantic:– Early fisheries science was
largely influenced by oceanography (e.g., Henry Bigelow, 1879–1967).
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Fishing and the Environment• Several scientific debates and initiatives
focused on the relative effects of fishing and the environment:– Huxley’s (1883) affirmation that the cod,
herring and mackerel fisheries were inexhaustible.
– Thompson-Burkenroad debates (1948-1953) on the overfishing vs. environmental factors as the cause of decline in the Pacific halibut stock.
– California Cooperative Oceanic Fisheries Investigations (CalCOFI) was formed to study the ecological aspects of the collapse of the sardine populations off California.
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Single-Species Stock Assessment• A convention for fishery science based on demographics
was formed in the 1950s (Ricker 1955, Beverton & Holt 1957;) in which overfishing and Maximum Sustainable Yield (MSY) were estimated through age-based models.
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Recruitment Dynamics• Cushing (1982) illustrated the
importance of climate, primary & secondary production as factors explaining recruitment variability.
• Sinclair (1988) demonstrated the importance of hydrographic processes in larval retention.
• Rothschild (1988, etc.) recognized the decadal scale of recruitment variability.
ASpawning
area
BNursery
area
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entDen
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ontra
nata
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area
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area
Adult stock
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Denatant
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entDen
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ontra
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Environmental Variability• Simulation is now
used to incorporate environmental variability in the traditional demographic stock assessments (Mace 2001)
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MAR545 22-Ecosystems 8
Environmental Change• Environmental factors can modify the Stock-
Recruitment relationship.
0.0
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Challenges for Fisheries Management• Predictability of future environments
– If the environment strongly influences fish productivity and can be reliably projected, fisheries can be managed accordingly (e.g., Pacific sardine; MacCall 1995, Hill et al. 2007).
– When the environment cannot be reliably projected, we only have a retrospective understanding of fishery variability.
• A new form of understanding through simulation– Operating models can be used to represent biological and
environmental realism.– Simple stock assessment models can be evaluated in the context of a
more complex world.– Fishery management strategies can be designed to take advantage of
favorable environments while being robust to variability.
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Cod, Climate and Complexity• Objective: examine the impacts of climate change on the
productivity, stability, and sustainable yield of U.S. cod populations.
– Complexity: recent genetic data shows that population structure is composed of three primary spawning components.
– Climate Change: increased water temperature and storms influence recruitment and growth of each spawning component.
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Spatial Complexity• Fishery management units were
based on fishing grounds.• Genetics, movement, growth, etc.
indicate more complex structure.• Spatial complexity confers greater
productivity and resilience than the management unit perception.
Georges Bank
Gulf of Maine
NorthernSpawningComplex
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BankSouthernSpawningComplex
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Yield (k
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Climate Change• Environmental effects on recruitment:
– Retention of larval cod is strongly correlated to mean northward wind velocity (Churchill et al. 2011).
– Winter storms are strongly associated with temperature (e.g., Emanuel 2005).
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Complexity and Climate Simulations of Cod• We estimated spawning group-specific temperature effects.• We simulated response of cod populations to sea surface
temperature (SST) across a range of fishing mortality (F)– Baseline model: Mean and standard deviation of SST– Low CO2 emissions scenario: Mean & Std.dev. + 1°C
– High CO2 emissions scenario: Mean & Std.dev. + 2°C
• Response metrics: – Productivity: spawning stock biomass (SSB)– Sustainable yield: maximum sustainable yield (MSY) and FMSY
– Stability: coefficient of variation (CV) in SSB
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Climate Change• Temperature (T) effects on cod production:
– Recruitment (R) as a function of spawning biomass (S) is negatively affected by warming (Fogarty et al. 2008):
– Size at age (wa) is positively affected by warming (Brander 1995):
– Fishery production decreases with warming.
TSSeR
)(1 aThga e
Ww
Fishing Mortality
Fish
ery
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il t)
1982-2003 mean T
+1oC
+2oC
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0
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ProductivityNorthern Spawning Complex SSB as Temperature
Southern Spawning Complex SSB as Temperature
Eastern Georges Bank SSB as Temperature
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0
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Catc
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Cat
ch (
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Catc
h (m
T)
Fishing Mortality
Baseline modelClimate change (+ 1 degree)Climate change (+ 2 degree)
Sustainable YieldNorthern Spawning Complex MSY as Temperature
Southern Spawning Complex MSY as Temperature
Eastern Georges Bank MSY as Temperature
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StabilityNorthern Spawning Complex CV as Temperature
Southern Spawning Complex CV as Temperature
Eastern Georges Bank CV as Temperature
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MetapopulationResponse
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Cat
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Baseline modelClimate change (1 degree)Climate change (2 degrees)
Productivity SSB as Temperature
Yield MSY as Temperature
Stability CV as Temperature
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Conclusions• Climate change differentially influences cod
spawning groups based on the timing and location of spawning and different growth environments of each population.
• Spatio-temporal population structure is important for determining sensitivity to climate change.
• Simulation, the operating model concept, and management strategy evaluation offer new tools for fisheries oceanography.