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Juvenile salmon survival in coastal waters of the Northeast Pacific Ocean: top-down or bottom-up control?

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Research Funded by GLOBEC. Juvenile salmon survival in coastal waters of the Northeast Pacific Ocean: top-down or bottom-up control?. Vladlena Gertseva, Thomas Wainwright, Vladimir Gertsev October 19, 2004 PICES XIII Annual Meeting. Why juveniles?.

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slide1

Research Funded by GLOBEC

Juvenile salmon survival in coastal waters of the Northeast Pacific Ocean: top-down or bottom-up control?

Vladlena Gertseva, Thomas Wainwright, Vladimir Gertsev

October 19, 2004

PICES XIII Annual Meeting

slide5

Upper Trophic Levels

Top-down

Bottom-up

Lower Trophic Levels

Juvenile Salmon

research objectives
Research objectives
  • Summarize knowledge on juvenile salmon interactions in coastal oceanic waters
  • Develop a mathematical model of juvenile salmon dynamics
  • Identify processes controlling the survival of juvenile salmon
slide7

Number of Fish N(t)

Fish Weight W(t)

Total Biomass B(t)

slide8

Top-down

Bottom-up

N(t)

Initial weight, W0

W(t)

Initial number, N0

Maximum weight, Wmax

Y

Trophic coefficient, kT

Resources

Competition

Anthropogenic effect

B(t)

N(t)

W(t)

Natural mortality

Stochastic elimination

Food availability

Temporal migrations

Trophic demands

Cannibalism

Predation

Temperature

Salinity

Light

Dissolved oxygen

modeling individual growth

Juvenile stage

Modeling individual growth

W0 – initial weight of fish

Wmax– maximal weight of fish

Q1 – buffer coefficient

kT – trophic coefficient

t – time

modeling fish abundance
Modeling fish abundance

N0– initial number of fish Y – additive loss Q2– buffer coefficient t – time

slide11

Coho salmon

1999 – 2002

May, June, September

  • Fish abundance
  • Fish weight
  • Temperature
  • Salinity
  • Trophic demands
  • Abiotic preferences
slide12

Individual weight

Total biomass

Number of fish

90

180

Days

0

45

135

Model simulations

sensitivity analysis
Sensitivity analysis
  • Vary the values of different parameters
  • Record the response of the juvenile salmon
  • Determine the most important factors
slide14

Model predictions

effect of variations in predation on total biomass

Total Biomass

150000

1:Predation=0.03 2:Predation=0.035 3:Predation=0.04 4:Predation=0.045 5:Predation=0.05

75627

1255

90

180

0

45

135

Days

slide15

Total Biomass

90

180

0

45

135

Model predictionseffect of variations in trophic coefficient on total biomass

150000

1:Trophic coefficient=1 2:Trophic coefficient=0.95 3:Trophic coefficient=0.9 4:Trophic coefficient=0.85 5:Trophic coefficient=0.8

75627

1255

Days

conclusions
Conclusions
  • Juvenile salmon biomass in the coastal waters is primarily defined by variations in activity at upper trophic levels rather than lower ones
  • Juvenile salmon survival is primarily controlled by a top-down, but not a bottom-up mechanism in the nearshore oceanic ecosystem
theoretical implications
Theoretical implications
  • Provides a theoretical insight into complicated relationships between juvenile salmon and their environment
  • Enables a simultaneous study of both upper and lower trophic level effects
  • Sets the range of data necessary for studying the survival of juvenile salmon
  • Defines future research priorities
research priority
Research priority
  • Study predators
  • Abundance
  • Food habits
  • Feeding rates