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) vincent.vallee@ifremer.fr

Ilan Perez MS Candidate

ilanperez.perso@gmail.com &

Thank you !

Vincent Vallée, Ilan Perez, Maria Ching Villanueva & Fabian Blanchard