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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 !!!