Functional response in a size‐based world:modelling trophic interactions in the Benguela 

ecosystem using Osmose‐Npzd‐Roms

Yunne SHINMorgane TRAVERS

IRD (Institut de Recherche pour le Développement)CRH (Centre de Recherche Halieutique Méditerranéenne et Tropicale)

Sète, France

ECEM 07, 27-30 November, 2007, Trieste, Italy

Functional response (FR)

Definition :

Quantity of prey consumed by a predator by unit of space and time.

Function linking predator and prey dynamics in trophic models.

Common functional responses

F(N) = aN F N b Nbt Nh

( ) =+1 F N b N

bt Nh( ) =

+

2

21

th-1 th

-1

F(N) F(N)F(N)

0 00N N N( ) (b) ( )

Lotka-Volterra Holling II Holling III

Prey biomass

FR

FR‐ synthesis

No interaction between predators (« laisser-faire »)

a = b N F b Nbt Nh

=+1

type II Holling

a = b N2 F b N

bt Nh

=+

2

21 type III Holling

Interference between predators

a QNP

n

m= Ft N

Qt P Nh

n

hm n=+

−

−

1

1( ) Hassel and

Varley 1969

a QN

P P=

+( )

0 F

t NQt P P N

h

h=

+ +

−

−

1

10( ) ( )

De Angelis et al. 1975

a Q NN P

=+

( ) FQ t N

t P Nh

h=

+

+ +

−

−

( )( )

11

1

1 Getz 1984

Interference and ratio-dependence a Q N

P

n

= ⎛⎝⎜

⎞⎠⎟

( )( )

FQ N P

Q N P

n

n=

+

/

/1

Arditi and Ginzburg 1989

FR‐ Does it matter?

B prey

FRType III

Large choice of FRs, but does it matter?

How to choose?

► No empirical support, conceptual framework

► Pragmatic choice

► Parameterization problem Type II

L-V

FR in models of marine ecosystems

Formalism

Deterministic functional response FR

Constant predation rate

Emerging functional response

IBM

model hypotheses parameterization

Ecosim: modified L-V function-Natural refuge for prey- prey preference

- All parameters from Ecopath- Diets composition data

Nemuro.Fish

Atlantis: Holling II

- No interaction between predators- Prey preference

- Half-saturation K by calibration, max ingestion rate- Diets composition data

Apecosm: size-based Holling II - Size-based predation- No interaction between predators

- Half-saturation K by calibration, max ingestion rate-Predator size selection function

Osmose: multispecies IBMSize-based opportunistic predation

- Max ingestion rate- Pred/prey size ratio

Huse & Fiksen: behavioural small scale IBM

Importance of light and turbulence in predator/prey encounter rate

Many individual parameters

OSMOSEObject‐oriented Simulator of Marine ecOSystems Exploitation

Shin & Cury 2001, 2004

Variability in time and space of fish dietsCannibalismOmnivory

Patterns in fish diets

Main predation mechanism

opportunistic predationsize-based predation

OSMOSE: Fish life cycle

3 constraints:

► predator/prey size ratio

► spatio-temporal co-occurrence

► maximum ingestion rate

Predation efficiency ξ

Spatial distribution

Natural mortality

Forage

Predation

Starvationξ

Growth

Fishing mortality

Reproduction

ξ

Ratio max

Ratio min

pred size

Prey size

#

#

#

#

#

#

Gansbay

Lamberts Bay

Saldanha Bay

Port ElizabethHout Bay

St Helena Bay

200 m

500 mLamberts Bay

16 18 20 22 24 26 28

-36 -36

-34 -34

-32 -32

0 200 400 Km

#

#

#

#

#

#

Gansbay

Lamberts Bay

Saldanha Bay

Port ElizabethHout Bay

St Helena Bay

200 m

500 mLamberts Bay

16 18 20 22 24 26 28

-36 -36

-34 -34

-32 -32

0 200 400 Km

Modelled food webs are variable in structureOpportunistic predation: dampening role on the foodweb

Forcing/coupling: E2E approach

Spatial distribution

Natural mortality

Forage

Predation

Starvation

Growth

Fishing mortality

Reproduction

Food availability

Bt,x,y,i

Predation mortality

Mt,x,y,i

(Travers and Shin, submitted)

ROMS-N2P2Z2D2(Penven, Machu, Koné)

Flagellates Diatoms

Copepods

Nitrates

Large detritus

Ciliates

Small detritus

Ammonium

20 µm

200 µm20 µm20 µm2 µm

2 mm200 µm200 µm

PROCESSES: Grazing, growth, excretion, egestion, mortality, sinking, photosynthesis, respiration, nitrification, remineralization

Application southern Benguela12 fish species modelled: 76% total fish biomass, 94% total catch

Lanternfish Lightfish

Anchovy

Sardine

Redeye

Chub mackerel

Horse mackerel

Shallow water hakeDeep water hake

Snoek

Silver kob

Kingklip

TL distributions (1): Large omnivorous species

TL OSMOSE TL ECOPATH

TL

Den

sity

silver kob kingklip

shallow-water hake deep-water hake snoek

FR for large omnivorous species ??

2600000 3000000 3400000

0.04

00.

050

0.06

00.

070

8.0 e+06 1.0 e+07 1.2 e+07

0.03

00.

035

0.04

00.

045

6.0 e+06 8.0 e+06 1.0 e+07 1.2 e+07

0.02

0.03

0.04

0.05

8.0 e+06 1.0 e+07 1.2 e+07 1.4 e+07

0.04

0.05

0.06

0.07

0.08

8.0 e+06 1.0 e+07 1.2 e+07 1.4 e+07

0.03

50.

045

0.05

50.

065

silver kob kingklip

shallow-water hake deep-water hake snoek

Sum ( prey)

Multispecies FR

TL distributions (2): Small pelagic species

TL OSMOSE TL ECOPATH

TL

Den

sity

anchovyanchovyeuphausiidlanternfishredeyedinoflagdiatomciliatecopepod

horse mackerel

euphausiids lantern fish

TL distributions (2): Small pelagic species

TL OSMOSE TL ECOPATH

TL

Den

sity

anchovyanchovyeuphausiidlanternfishredeyedinoflagdiatomciliatecopepod

anchovy horse mackerelhorse mackerel

euphausiidseuphausiids lantern fishlantern fish

Emergent FR for small pelagic species

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

3.E+06 8.E+06 1.E+07 2.E+07Biomass copepods

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.03

0.04

0.05

0.06

0.07

0.08

0.09

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

Emergent FR for small pelagic species

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

3.E+06 8.E+06 1.E+07 2.E+07Biomass copepods

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.03

0.04

0.05

0.06

0.07

0.08

0.09

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

B copepods

2.E+06

4.E+06

6.E+06

8.E+06

1.E+07

1.E+07

1.E+07

2.E+07

2.E+07

jan febmar ap

rmay jun julau

gse

p oct novdec

Emergent FR for small pelagic species

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

3.E+06 8.E+06 1.E+07 2.E+07Biomass copepods

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.03

0.04

0.05

0.06

0.07

0.08

0.09

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

B copepods

2.E+06

4.E+06

6.E+06

8.E+06

1.E+07

1.E+07

1.E+07

2.E+07

2.E+07

jan febmar ap

rmay jun julau

gse

p oct novdec

0.E+00

5.E+05

1.E+06

2.E+06

2.E+06

3.E+06

3.E+06

jan feb mar apr

may jun jul aug

sep oct

nov

dec

anchovyeuphausiidhorsemacklantern

FR: Ratio‐dependent?

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

3.E+06 8.E+06 1.E+07 2.E+07Biomass copepods

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.03

0.04

0.05

0.06

0.07

0.08

0.09

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR: Ratio‐dependent?

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

3.E+06 8.E+06 1.E+07 2.E+07Biomass copepods

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR anchovy

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

8.E+00 2.E+01 3.E+01 4.E+01

B copepods/B anchovy

FR horse mackerel

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

6.E+00 2.E+01 3.E+01

B copepods/B horse mackerel

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.03

0.04

0.05

0.06

0.07

0.08

0.09

3.E+06 8.E+06 1.E+07 2.E+07

Biomass copepods

FR lanternfish

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

2.E+00 1.E+01 2.E+01B copepods/B lanternfish

FR euphausiid

0.00

0.01

0.01

0.02

0.02

0.03

0.03

0.E+00 1.E+01 2.E+01

B copepods/B euphausiid

Conclusion

Exploration of emergent species functional responses when size-based opportunistic predation.

Patterns emerge when predator species are specialists, or are dominant in biomass.When copepods are the dominant prey:

► ratio-dependent FR when predator species are dominant: euphausiids, mesopelagic fish

► for anchovy, horse mackerel, redeye, sardine:type III FR when seasonal decrease in copepods production type II FR when seasonal increase copepods production

Csq in end-to-end modelling: choice of FR when coupling models of high trophic levels (fish) and models of low TL (npzd type) would depend on predators omnivory, on plankton seasonal production and on relative dominance of predators

No patterns for large omnivorous fish species (cf economic/cost approach Mullon et al. on Friday morning)

GRAZIE MILLE !!!