Individual variation and migration

Dr. Steven Cooke

Fish Ecology and Conservation Physiology Lab

Carleton University, Ottawa

Dr. Kathryn Peiman

Lake Ontario Atlantic Salmon

Restoration Program

Coordinator, OFAH

Why care about individual variation?

Why care about individual variation?

• The stuff of natural selection

• Not due to age or sex

• Individual differences in:• behaviour: bold-shy; aggressive; exploratory -> personality

• physiology: metabolic rate, hormones, immunity

• morphology: feeding; movement -> resource polymorphism

• life history: life span, fecundity, age at maturity -> r vs k selection

• Feedback among categories (cause/effect)

• Genetic vs induced by the environment

• Consistent over time vs flexible

Réale et al 2010 Phil Trans Roy Soc B

Stressors affect variation

Killen et al. 2013 Trends in Ecology and Evolution

Mild stressor (differential sensitivity to stressor)

Severe stressor (single best response)

• what happens during one part of your life affects outcome during another part

• causes and consequences

Carryover effects

• feeding location in the ocean affects ability to migrate/spawn (fitness consequence of carryover effect)

• successful migrators/spawners were offshore, feeding at a lower trophic level (more –ve stable isotopes)

Sockeye salmon (British Columbia)

320 km

40 km

Final (death) Initial (near-end migration) endogenous resources carryover effect

scale, adipose scale, adipose, blood

Do successful migrators/spawners have different initial isotope values than failed migrators/spawners?

2-27 days

Do successful migrators have different initial isotope values than failed migrators?

x

No – but only 6 failures

Do successful spawners have different isotope values than failed spawners?

Males: Are isotope values related to morphology?

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δC scale initial

Carryover effect: initial values – no

Other effects

• Males: more enriched δC and δN, later capture date (scale, adipose, and blood)

• Carryover effect – assuming early arrival is good

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Migration date

Brown trout (Denmark)

• partial migration

• migrant vs resident phenotype

• individual threshold controlled by genetics,

environment

• timing of migration within migratory phenotype

• natural variation contributes to both (body condition,

body size, growth rate)

• manipulated variation (causes of carryover effect)

• chase, food deprivation, temperature increase

• cortisol – hormone released when hypothalamic-

pituitary-interrenal axis activated; mimicking ‘stress

response’Peiman et al. 2017 Oecologia

Natural variation: the migrant vs resident phenotype

Small, poor-condition individuals were migratory

• constrained by low food availability

• empirical evidence mixed

Treatments had no effectMigratory

Resident

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Migration date (Oct 26 = day 1)

control

thermal challenge

chase

food deprivation

cortisol

sham

June 15Oct 26

Stress affects migration date: cortisol treated fish migrated earlier

cortisol

Low growth-rate individuals under stress migrated earlier

Thermal stress

Food deprivation

...unexpected result!

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Specific growth rate (% day-1)

May 19

White suckers (Ontario)

• tagged fish returns (2018)

• individual consistency across years

• predictors of skip spawning (cortisol -> physiology;

morphology; timing -> behaviour; diet)

What are the

correlates of

migration timing?

Cobourg Creek

Correlates of migration timing: date of migration (behaviour) and physiology

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Causes:-lake conditions?-contaminants?-physiology?

Consequences:-reproduction?-skip spawning?

Stressors affect variation

Killen et al. 2013 Trends in Ecology and Evolution

-food availability, distribution-density-hypoxia-water velocity-predation risk-temperature-pollutants-dehydration-refuge availability-anthropogenic noise, light

-change the amount of variation present on which natural selection can act-select for certain phenotypes

Example: low food -> high MR lose mass -> bolder -> more predation -> low fitness for high MRExample: repeated temp changes -> flexibility -> optimal conditions -> high fitness for flexibility

BC:

Steven Cooke, Michael Power, David Patterson, Scott Hinch, Matt Casselman, N’QuatquaFirst Nations, St’át’imctechnicians

Denmark:

Steven Cooke, Kim Aarstrup, Kim Birnie-Gauvin, Martin Larsen, Jon Midwood, Alex Wilson

Acknowledgements