The effects of climate change and the collapse of the shrimp fishery on fish communities’ diversity and ecological functions in a tropical context:
The case of the continental shelf off French Guiana
4th International Symposium ECCWO, June 4-8, 2018, Washington DC
Vincent Vallée1, Ilan Perez1, Maria Ching Villanueva2 & Fabian Blanchard1
1 Ifremer Guyane, Fisheries Biodiversity Unit UMSR LEEISA, University of Guyane - CNRS - Ifremer
2 Ifremer Centre de Bretagne, Fisheries Biology Laboratory
Ven. Col.
Local context
A high fish diversity between 400 and 500 species 1
• An increasing SST (sea surface temperature)
T (°
C)
Local context
2
27
27.5
28
28.5
29
29.5
1990 1995 2000 2005 2010 2015
+1 °C
• A collapsing fishing pressure by bottom trawling (shrimp fishery)
• An increasing SST (sea surface temperature)
T (°
C)
Local context
2015 2010 2005 2000 1995 1990
Shrim
p la
ndin
gs (t
.)
Days
at t
he se
a
2
27
27.5
28
28.5
29
29.5
1990 1995 2000 2005 2010 2015
+1 °C
Describe the effects of climate change and a decreasing fishing pressure on tropical fish communities
Provide a better understanding of the tropical fish communities’ functioning in order to plan how they could respond to future climatic and fishing scenarios Set up future ecological and economic implementations
Objectives and interests
3
Samplings
RESUBGUY CHALOUPE STUDY
10 m
60 m
33 stations
4
1993 2017
Samplings
RESUBGUY CHALOUPE STUDY
1993
1994
2006
2007
2009 2014
2017
2016
1990’s 2000’s 2010’s 4
Functional diversity: the traits based approach
14 morphological traits 2 ecological traits
Measured from 1 to 10 collected individuals for 174 species
• Trophic group - planktivorous - invertivorous - piscivorous - omnivorous • Habitat - benthic - demersal - pelagic
Modified from Villéger et al., 2010
Functional Richness (FRic), Functional Dispersion (FDis) Functional Specialization (FSpe)
5
Functional indices
Functional richness (FRic)
Convex hull = FRic
FRic = the portion of the functional space filled by a species assemblage
6
Trait 1
Trai
t 2
Functional indices
Functional richness (FRic)
FRic of the last three decades
FRic of one decade
FRic = the portion of the functional space filled by a species assemblage
Trait 1
Trai
t 2
6
Functional indices
Functional richness (FRic) ! Rare species
with an extreme
combination of traits
FRic = the portion of the functional space filled by a species assemblage
Trait 1
Trai
t 2
Trait 1
Trai
t 2
6
Functional indices
Functional richness (FRic)
FDis = abundance weighted deviation of species trait values from the center of the functional space filled by the community
Functional Dispersion (FDis)
FRic = the portion of the functional space filled by a species assemblage
Trait 1
Trai
t 2
Trait 1
Trai
t 2
6
Taxonomic indices
***
*** *
***
*** ns
Shannon exponential (H’) Species richness (S)
7
Functional indices
***
*** ns
***
*** ns
Functional Dispersion (FDis) Functional richness (FRic)
The same trend is observed for the functional specialization (FSpe) 8
Morpho-ecological groups
Benthic fish
Rays Reef fish
Demersal fish
Pelagic fish
9
Morpho-ecological groups
10
Reef fish
Demersal fish
Pelagic fish
Rays
Benthic fish
Total Biomass
100
1000
Biom
ass (
kg)
1990’s 2000’s 2010’s
Morpho-ecological groups
10
Reef fish
Demersal fish
Pelagic fish
Rays
Benthic fish
Total Biomass
x 3.5
x 3.7
Effects of the decreasing
fishing pressure
100
1000
Biom
ass (
kg)
1990’s 2000’s 2010’s
Size Spectra Slope (SSS)
11
-2.4
-2.2
-2
-1.8
-1.6
-1.4
-1.2
1990 1995 2000 2005 2010 2015 2020
Size
spec
tra
slope
log
(abu
ndan
ce)
log (size class median)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1.1 1.6 2.1
2010’s
1990’s
Mean Temperature of the Survey Community (MTSC)
Cheung et al., 2013
Mean annual SST
T (°
C)
12
2525.5
2626.5
2727.5
2828.5
2929.5
1990 1995 2000 2005 2010 2015 2020
+1 °C
+1.2 °C
MTSC
Mean Temperature of the Survey Community (MTSC) T
(°C)
Tropical species
Sub-tropical species Mean B = 2 t Mean B = 2.57 t Mean B = 2.86 t 12
1990’s 2000’s 2010’s
2525.5
2626.5
2727.5
2828.5
2929.5
1990 1995 2000 2005 2010 2015 2020
+1 °C
+1.2 °C
Mean annual SST
MTSC
Cheung et al., 2013
90%
0%
0%
4%
41%
47%
0.5%
53%
38%
The Rays group
1990’s 2000’s 2010’s
0
100
200
300
400
500
600
700
800
900
1990 1995 2000 2005 2010 2015 2020
Hypanus_americanus
Hypanus_guttatus
Fontitrygon_geijskesiBiom
ass (
kg)
Tropical species
Sub-tropical species
13
H. americanus
H. guttatus
F. geijskesi
Restructuring of the fish communities so far but until when ?
Synthesis
Ilan Perez, Ifremer © 14
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
Mean SST of the 1990’s
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
Mean SST of the 1990’s
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
Mean SST of the 1990’s
Mean SST of the 2010’s
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
Mean SST of the 1990’s
Mean SST of the 2010’s
What’s next about SST ?
15
T (°
C)
Species rank
5
10
15
20
25
30
Mean SST of the 1990’s
Mean SST of the 2010’s
Estimated mean SST for 2050 (30°C?)
Biodiversity in tropical regions is likely to be impacted by higher rate of local extinction due to warming waters In French Guiana, positive effects of the decreasing fishing
pressure on the fish communities’ dynamics dominates over the climate change so far
16
Conclusions
French Guiana
SST (°C)
Biodiversity in tropical regions is likely to be impacted by higher rate of local extinction due to warming waters In French Guiana, positive effects of the decreasing fishing
pressure on the fish communities’ dynamics dominates over the climate change so far
Ecosystem approach to fisheries management Mechanistic approaches to evaluate impacts of future scenarios on fish communities
16
Conclusions
French Guiana
SST (°C)
Vincent Vallée PhD Student (2016-2019) [email protected]
Ilan Perez MS Candidate
Thank you !
Vincent Vallée, Ilan Perez, Maria Ching Villanueva & Fabian Blanchard