Physiological model of krill (Meganyctiphanes norvegica and Thysanoessa raschii) in the !Estuary and Gulf of St-Lawrence

Déborah BENKORT

Supervised by Frédéric MAPS, Stéphane PLOURDE et Diane LAVOIE

Theme 1: Spatial-temporal

distribution and abundance!

Theme 2: Key processes

of krill ecophysiology!

Theme 3: Bio-

physical modelling !

Theme 4: Consumption and energetic requirements

of krill dependent species –

marine mammals

Theme 5:Trophic

ecosystem modelling!

"!

Production and consumption of krill

in the Gulf of St. Lawrence

toward an ecosystem-based stock assessment

!

Introduction Objective Methods Results and discussion Conclusion

#!

What is krill?

! Macrozooplankton (> 2 cm)

! Live in large aggregations

! Forage species

Why focus on krill ?

! Ecological importance (i.e. food web)

! Economic importance (i.e. krill oil)

Introduction Objective Methods Results and discussion Conclusion

$!

Thysanoessa raschii Meganyctiphanes norvegica

Eurythermal

Herbivorous <"CARNIVOROUS

Summer breeding

Stenothermal

HERBIVOROUS > carnivorous

Spring breeding

Large physiological and biological differences …

… but similar ecological role

%!&&!%!&&!

%!

Estuary and Gulf of St. Lawrence (EGSL)!Semi-enclosed seaEstuarine and cyclonic circulationSpatio-temporal variability

Study area

%!

Cohabitation of arctic and boreal species

Seasonnal ice cover ! Warm/cold water masses!

Introduction Objective Methods Results and discussion Conclusion

'!

Physiological statePhysiological

Introduction Objective Methods Results and discussion Conclusion

Swimming behavior

Gross production Population dynamics!Population

(!

Develop a species-specific physiological individual based model (IBM) and assess the

impacts of environmental variability at different spatio-temporal scales on the

production potential of krill

Introduction Objective Methods Results and discussion Conclusion

)!

Individualphysiological

model

Growth(mass)

Adult development (moulting)

(length)

Environmental forcing

*!!!

Introduction Objective Methods Results and discussion Conclusion

Temperature [Food]

+!

Growth =

I = A * food2 * V

1 + Th * V * food2

Holling type IIIFood dependant Temperature dependantAllometric relationship

Respiration (metabolism)Temperature dependantAllometric relationship

!!!!!!!!!!!! R = R0*M3/4*exp -Ei(T-T0)(kTT0)

!

Data from other themes

of Krill’s project

ingestion! – metabolism !

Introduction Objective Methods Results and discussion Conclusiondiscussion

,-!

Intermoult period (IMP) = 20.62 - 1.16*temperature

Adult development (moulting)

Moult(n)

Moult(n+1)

When 40 % of IMP reachedMoulting type decided and engaged

Pre-decision phase (40%) Post-decision phase (60%) phase (40%) Post-

!./0!

Introduction Objective Methods Results and discussion Conclusiondiscussion

Ref : Sameoto, D. D. (1976). "Respiration Rates, Energy Budgets, and Molting Frequencies of Three Species of Euphausiids Found in the Gulf of St. Lawrence." Journal of the Fisheries Research Board of Canada 33(11): 2568-2576.

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Variable food concentration Constante temperature = 12°C

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Constante food concentration = 0.2 mgC.l-1 Variable temperature

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Introduction Objective Methods Results and discussion Conclusiondiscussion

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Introduction Objective Methods Results and discussion Conclusiondiscussion

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Variable food concentration Constante temperature = 12°C

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Constante food concentration = 0.2 mgC.l-1 Variable temperature

Introduction Objective Methods Results and discussion Conclusion

Convergence towards an target mass and size in the model

Tend to achieve energy balance and reach an equilibrium

In the model, individuals tend towards an optimal mass/size ! how does it compare with natural environmental plasticity

Still lacking: behavioural costs, other metabolic costs – maturation, excretion, etc -, senescence and reproduction.

F

discussion

Introduction Objective Methods Results and discussion Conclusion

,$!

Coupling a regional advection model

! Better understanding of its

distributions

! Get areas of production

!!!

discussion

understanding

Current outcome

Realistic representation of production thanks to innovative coupling of growth (mass) and moulting (size)

Next step

Theme 3: Bio-physical modelling!

Theme 1: Spatial-temporal

distribution and abundance!

Theme 2: Key processes of

krill ecophysiology!

Theme 5:Trophic

ecosystem modelling!

,%!

Thank you for your attention !!!!Questions ?!

Acknowledgement :My supervisers, neolab members, and the members of 4085 office

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