Download Defining functional groups in fish communities: - usefulness

Defining functional groups in fish communities:
usefulness of ecomorphology
Yves Reecht1 , Marie-Joëlle Rochet1 , Verena Trenkel1 ,
John K. Pinnegar2 and Simon Jennings2
1 Dpt
2 CEFAS
EMH, IFREMER Nantes, France
Lowestoft Fisheries Laboratory, UK
Colloque Approche Systémique des Pêches/Ecosystem Approach to Fisheries
– Boulogne-sur-mer – 5 Nov. 2008
General purpose
Presentation
Content
Approach
Context
Chosen approach
Method
Context
PhD on indicators of impact of fishing on structure and dynamics
of marine food-webs
Results
Perspectives
Approach
Functional structure
∼
indicator of fishing impact
⇒ structure easy to assess with standard surveys data?
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Choice of an ecomorphological approach
Presentation
Content
Approach
Context
Usual approaches
Size-based:
Trophic function
summarised by size
Species-based:
fonctions assumed
homogeneous within species
Chosen approach
Method
size × species ?
Results
Perspectives
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Choice of an ecomorphological approach
Presentation
Content
Approach
Context
Usual approaches
Size-based:
Trophic function
summarised by size
Species-based:
fonctions assumed
homogeneous within species
Chosen approach
Method
size × species ?
Results
Perspectives
⇓
Ecomorphological approach
Hypotheses: morphology–ecological function relationships
⇒ functional traits.
Advantage: No a priori knowledge of ecological functions
required.
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Choice of an ecomorphological approach
Examples of functional traits
Presentation
Content
Predation function:
Approach
Context
Chosen approach
Method
Results
Perspectives
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Choice of an ecomorphological approach
Examples of functional traits
Presentation
Content
Predation function:
Approach
Context
Chosen approach
mouth size
Method
Results
Perspectives
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Choice of an ecomorphological approach
Examples of functional traits
Presentation
Content
Predation function:
Approach
Context
Chosen approach
mouth size
Method
Results
Perspectives
Body depth
standard length
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Choice of an ecomorphological approach
Examples of functional traits
Presentation
Content
Predation function:
Approach
Context
Chosen approach
mouth size
Method
Results
Perspectives
Body depth
standard length
caudal fin aspect ratio
Colloque ASP/EAF – 05/11/2008
cfar =
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h2
A
Choice of an ecomorphological approach
Examples of functional traits
Presentation
Content
Predation function:
Approach
Context
Chosen approach
mouth size
Method
Results
Perspectives
Body depth
standard length
caudal fin aspect ratio
digestive tract length
standard length
...
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Functional groups definition
Steps
Presentation
Content
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Colloque ASP/EAF – 05/11/2008
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Functional groups definition
Steps
Presentation
Content
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Colloque ASP/EAF – 05/11/2008
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Functional groups definition
Steps
Presentation
Content
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Colloque ASP/EAF – 05/11/2008
5/14
Functional groups definition
Steps
Presentation
Content
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Colloque ASP/EAF – 05/11/2008
5/14
Functional groups definition
Steps
Presentation
Content
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Colloque ASP/EAF – 05/11/2008
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Probabilities to belong to groups
Presentation
Content
A key role
(c.f. general purpose)
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
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Probabilities to belong to groups
Presentation
Content
A key role
(c.f. general purpose)
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Within-species functionally homogeneous size-classes
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Probabilities to belong to groups
Presentation
Content
A key role
(c.f. general purpose)
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Within-species functionally homogeneous size-classes
⇓
p(F1, F2,. . . ,Fi) = f(size, species)
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Probabilities to belong to groups
Presentation
Content
A key role
(c.f. general purpose)
Approach
Method
Functional groups
Groups probabilities
Validation
Results
Perspectives
Within-species functionally homogeneous size-classes
⇓
p(F1, F2,. . . ,Fi) = f(size, species)
⇓
Individuals with functional traits not measured:
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Relationships with diet
Presentation
Content
Hypothesis: Diet is an outcome of the potential predation
function
Approach
Method
⇒ partially constrained by functional groups
Functional groups
Groups probabilities
Validation
Results
Perspectives
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Relationships with diet
Presentation
Content
Hypothesis: Diet is an outcome of the potential predation
function
Approach
⇒ partially constrained by functional groups
Method
Functional groups
Groups probabilities
Validation
Results
Tests:
RDA: diet variance explained by functional
group probabilities
Perspectives
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Relationships with diet
Presentation
Content
Hypothesis: Diet is an outcome of the potential predation
function
Approach
⇒ partially constrained by functional groups
Method
Functional groups
Groups probabilities
Validation
Results
Tests:
RDA: diet variance explained by functional
group probabilities
Perspectives
Explained matrices: proportions of. . .
prey habitat
taxonomic groups
prey categories (based on digestibility, size,
mobility and habitat)
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Relationships with diet
Presentation
Content
Hypothesis: Diet is an outcome of the potential predation
function
Approach
⇒ partially constrained by functional groups
Method
Functional groups
Groups probabilities
Validation
Results
Tests:
RDA: diet variance explained by functional
group probabilities
Perspectives
Explained matrices: proportions of. . .
prey habitat
taxonomic groups
prey categories (based on digestibility, size,
mobility and habitat)
Similar analyses with size only groups
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Functional groups 1/3
Presentation
Content
Approach
FG
F1
F2
F3
Method
F4
Results
Functional groups
F5
Predictions
Potential predation function
benthic-small-prey omnivorous
water-column-small-prey omnivorous
benthic-low-mobilitysmall-hard preys-feeders
benthic-elusivesmall-hard preys-feeders
benthic-elusivelarge-hard-preys-feeders
Validation
Conclusion
F6
F7
water-column-small-hard-preys-feeders
water-column-small-soft-preys-feeders
F8
F9
water-elusive-medium-soft-preys-feeders
water-column-large-soft-preys-feeders
F10
benthic-small-soft-preys-feeders
F11
benthic-elusive-mediumsoft-preys-feeders
Perspectives
Colloque ASP/EAF – 05/11/2008
SG
A1.B3.C3
A1.B1.C3
A1.B2.C2
A1.B3.C2
A1.B2.C1
A1.B4.C1
A2.B2.C1
A2.B3.C3
A2.B4.C1
A1.B4.C3
A3.B2.C3
A3.B4.C3
A3.B1.C3
A2.B1.C3
A3.B2.C1
A3.B2.C2
A3.B3.C2
A3.B4.C1
A3.B4.C2
Characterisation/strategy
ambushed/suction
suction feeding
grazing
suction/grazing
hunter (adapted to turbid conditions)
swimming hunter, adapted to turbidity
hunter (adapted to turbid conditions)
slow swimming, ambushed
swimming hunter, adapted to turbidity
cruising hunter
ram feeding
cruising hunter
suction feeding
suction feeding
high manoeuvrability, adapted to turbidity
hunter
suction feeding
hunter, adapted to turbidity
hunter
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Functional groups 2/3
Presentation
Content
Approach
A size effect. . .
groups with different
size
Method
Results
Functional groups
Predictions
Validation
Conclusion
Perspectives
Colloque ASP/EAF – 05/11/2008
Group
F1
F2
F3
F4
F5
F6
F7
F8
F9
F10
F11
Length (mm)
141±
±39
119±
±54
193±71
204±102
563±
±224
239±65
201±93
323±62
459±64
225±147
639±
±184
9/14
Functional groups 2/3
Presentation
Content
Approach
A size effect. . .
groups with different
size
Method
Results
intra-species size effect
omnivorous, small
preys
=⇒
Functional groups
Predictions
carnivorous,
medium preys
=⇒
Validation
Conclusion
Perspectives
⇒
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carnivorous,
large preys
Functional groups 2/3
Presentation
Content
Approach
A size effect. . .
groups with different
size
Method
Results
intra-species size effect
Functional groups
Predictions
Validation
Conclusion
Perspectives
. . . but also a taxonomic one
in a same group:
inter-species size
differences
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Functional groups 2/3
Presentation
Content
Approach
A size effect. . .
groups with different
size
Method
Results
intra-species size effect
Functional groups
Predictions
Validation
Conclusion
Perspectives
. . . but also a taxonomic one
in a same group:
inter-species size
differences
Some species in only
one group
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Functional groups 3/3
Presentation
Content
The method. . .
Approach
Method
c.f. within-species size effect!
separate taxonomically
close species
Results
Functional groups
Predictions
Validation
Conclusion
Perspectives
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Functional groups 3/3
Presentation
Content
The method. . .
Approach
Method
Results
Functional groups
Predictions
Validation
separate taxonomically
close species
but gather taxonomically
distant species
Conclusion
Adapted to catch large,
benthic,elusive and hard to digest
preys
Perspectives
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Functional groups 3/3
Presentation
Content
The method. . .
Approach
Method
Results
Functional groups
Predictions
Validation
separate taxonomically
close species
but gather taxonomically
distant species
Conclusion
Perspectives
⇓
Adapted to catch large,
benthic,elusive and hard to digest
preys
Sign of ecological convergence ?
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Probabilities of groups
Within−species
size range (mm)
Functional group
Presentation
Content
F1
F2
F3
F4
F5
F6
F7
F8
0
F9 F10 F11
200
400
600
800 1000
Proportions
Species
black−bellied angler (27)
boarfish (26)
●
lemon sole (31)
dab (30)
Results
Functional groups
Predictions
red gurnard (31)
●
●
●
●
●
●
horse mackerel (29)
sprat (22)
blue whiting (24)
whiting (30)
hake (24)
silvery pout (5)
herring (29)
lesser−silver smelt (28)
●
John dory (28)
●
●
greater argentine (10)
●
●
●
●
●
●
●
●
●
●●
●
norway pout (27)
lesser−spotted dogfish (28)
megrim (25)
imperial scaldfish (19)
●
poor cod (32)
●
ling (8)
●
●
●
●
●
●
●
●
long−rough dab (26)
●
●
●
●
Colloque ASP/EAF – 05/11/2008
F3
F4
***
n.s.
F2
***
F1
***
n.s.
spurdog (8)
n.s.
Perspectives
●
●●
●
●
grey gurnard (32)
haddock (19)
1
●
●
●
cod (17)
mackerel (26)
●
●
●
●
spotted dragonet (29)
Conclusion
0.5
●
dragonet (28)
Validation
●
F5
F6
F7
●
***
Method
●
0.2
***
Approach
angler (29)
●
●
●
expd.plot.tmp$sp
thick−backed sole (31)
F8
Within group, inter−specific
size differences
F9 F10 F11
11/14
Constraints on diet
Presentation
Content
Coherence between prediction and diet
Approach
Method
Results
Functional groups
Predictions
Validation
Conclusion
Perspectives
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Constraints on diet
Presentation
Content
Coherence between prediction and diet
Approach
Method
Results
Functional groups
Predictions
Validation
Conclusion
Perspectives
Better explain diet than size only
Diet characteristics
taxonomic groups
prey categories
prey habitat
Colloque ASP/EAF – 05/11/2008
functional groups
36%
43.1%
51.1%
12/14
size groups
31.4%
34.3%
19.1%
Conclusion
Presentation
Content
Approach
Method
Results
The method. . .
revealed intricate size and taxonomic effects on predation
function
appeared sensible regarding diet
Functional groups
Predictions
Validation
provide additional information regarding size only
Conclusion
Perspectives
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Conclusion
Presentation
Content
Approach
Method
Results
The method. . .
revealed intricate size and taxonomic effects on predation
function
appeared sensible regarding diet
Functional groups
Predictions
Validation
provide additional information regarding size only
Conclusion
Perspectives
Advantages:
less expensive than stomach content analyses
potential rather than realised function (under certain
conditions)
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And then. . .
Presentation
Content
Abundances time-series
Approach
Method
Results
Perspectives
Quantifying fishing impact
functional groups relative
abundances /
index of functional structure
Colloque ASP/EAF – 05/11/2008
∼
index of fishing pressure
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