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Impact of climate change on the fish
community structure of the eastern
continental shelf of the Bay of Biscay
Jean-Charles Poulard(1) and Fabian Blanchard(2)
(1)
(2)
IFREMER. Laboratoire d'Ecologie Halieutique, Rue de l'Ile d'Yeu. BP 21105. 44311 Nantes Cedex 3. France
IFREMER. Ressources Halieutiques. BP 70. 29280 Plouzané Cedex. France
ICES symposium “The influence of Climate Change on North Atlantic Fish Stocks”, Bergen, Norway 11-14 May 2004
Introduction
 Many fish species are at their southern or northern
limit of distribution range in the Bay of Biscay
 Warming in Bay of Biscay was evidenced by
Koutsikopoulos et al (1998) for the period 19721993, the warming trend was confirmed for the
whole of the 1990s by Planque et al (2003) since 1989 the
Bay of Biscay is on average warmer than usual at all seasons and all locations
Introduction
 Community studies in regions of overlapping “polar” and
“temperate” species base their climate change attribution
on differential responses:
- marine polar fish species have tended to be stable or
decline in abundance
- temperate species at the same site have increased in
abundance
 So, we can expect that in the Bay of Biscay:
- abundance and biomass of cold or temperate water
species will tend to decline
- a contrario, abundance and biomass warm water
species will tend to increase
Data
Data used were collected
during 14 autumn
groundfish surveys carried
out :
- in 1973
- during the 1987-2002
period
The study area was
restricted to the area
sampled in 1973:
- latitudes between 48°30' N
and 43°30' N
- depth ranges from 15 to
200 m.
The number of hauls per
survey varied from 56 to
154.
-9 °
-8 °
-7 °
-6 °
-5 °
-4 °
-3 °
-2 °
-1 °
48 °
48 °
France
47 °
47 °
Bay of Biscay
46 °
45 °
44 °
46 °
Study area
Depth (m)
less than 50
50 - 100
100 - 200
200 - 500
500 - 1000
more than 2000
-9 °
-8 °
-7 °
45 °
44 °
-6 °
-5 °
-4 °
-3 °
-2 °
-1 °
Data provided by 1279 hauls were analysed.
Methods
 Standardised annual abundance indices of 56 fish taxa
present on average in at least 5% of the tows are used as
input in a Correspondence Analysis to detect trend in the
evolution over time of the fish abundance indices
Variables: 14 groundfish survey indices
Illustrative variables
Year
Latitude
Species
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002 Minimal Maximal Mean Range
Ammodytes tobianus
0
2
3
0
34
8 100
71
3
5
0
35
1
7
35
70 52.5
35
Argentina silus
0
38
21
1
12
42
12
7 100
17
5
2
0
0
45
75
60
30
Argentina sphyraena
15
20
13
14
21
29
27
52
38
19
5
6
41 100
25
70 47.5
45
Arnoglossus imperialis
4
7
5
8
10
20
11
14
23
27
45
25
84 100
-17
58 20.5
75
Arnoglossus laterna
4
2
6
14
35
45
45
32
83
29
6
16
72 100
-17
70 26.5
87
Standardised survey indices
Trachinus draco
Trisopterus luscus
Trisopterus minutus
Zeus faber
43
9
99
30
2
19
40
7
17
60
73
11
23
32
49
23
26
18
66
14
23
8
61
8
29
100
92
19
24
54
100
13
56
11
96
36
42
15
43
41
6
7
40
24
9
12
16
24
78
31
57
88
100
22
95
100
27
25
28
-47
66
65
66
63
46.5
45
47
8
39
40
38
110
 Latitudinal patterns of species are used to interpret the
temporal trends
Results
Correspondence Analysis first plan
Molva molva
Axis 2 - 13.46 %
Echiichthys vipera
Engraulis encrasicolus
Standardized abundance indices
Standar dized abundance indices
100
100
Scomber japonicus
75
Argentina silus
Hyperoplus lanceolatus
50
0.8
25
1997
75
50
25
0
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
Ammodytes tobianus
0
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
Dicologlossa cuneata0.4
Year
Pomatoschistus minutus
2000
1994
Buglossidium luteum
Large range species
Microstomus kitt
1998
Microchirus variegatus
1990
Conger conger
Capros aper
Low mean latitude
1995
-0.4
Squalus acanthias
Small range species
1988
1999
High mean latitude
1992 Sprattus sprattus
Molva molva
0.4
1987
Scomber scombrus
Enchelyopus cimbrius
Year
Lesueurigobius friesii
0.8
Pollachius
pollachius
1989 Mullus surmuletus
Echiichthys vipera
Axis 1 - 21.30 %
1.2
Gadiculus argenteus
Phycis blennoides
2002
Zeus faber
Merlangius merlangus
-0.4
Arnoglossus imperialis
2001
Chelidonichthys lucernus
1973
-0.8
Melanogrammus aeglefinus
Results
 Two species groups can be identified from the
species abundance trends observed over the study
period:
- abundances increased for 36 species (group A), the
majority of these species has a wide distribution range in
latitude and a low mean latitude distribution
- abundances decreased or fluctuated for 20 species (group
B), most of these species have a small distribution range
in latitude and a high mean latitude distribution
Results
Biomass changes
Species group B biomass
Species group A biomass
300
Biomass (1000 tons)
800
600
400
200
100
200
0
1970
1975
1980
1985
1990
Year
1995
2000
0
1970
1975
1980
1985
1990
Year
1995
2000
Species group B
Species group A
300
900
800
250
Biomass (1000 tons)
Biomass( 1000 tons)
Biomass (1000 tons)
1000
700
600
500
400
300
200
200
150
100
50
100
0
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
0
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
Year
Year
Latitude range
20-59
60-120
Latitude range
20-59
60-120
Results
Species group B - average length
20
20
19
19
18
18
17
17
Length (cm)
Length (cm)
Species group A - average length
16
15
14
13
16
15
14
13
12
12
11
11
10
10
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
Year
Year
The sharp decrease of the mean length of species group A (large range and
southern latitude species) is mainly due to increase abundance of small fish.
This effect seems due to climate change.
Results
Species group B - trophic level
4.2
4.2
4
4
Trophic level
Trophic level
Species group A - trophic level
3.8
3.6
3.4
3.2
3.8
3.6
3.4
3.2
3
3
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
1973 1987 1988 1989 1990 1992 1994 1995 1997 1998 1999 2000 2001 2002
Year
Year
The trophic level of species group B declined significantly from 1973 to 2002
(Mann-Kendall test S= - 45, P= 0.014)
Conclusions
 Changes in abundance and biomass observed in the fish
community can be explained by warming
 Decrease of mean length of group A can be explained by
increase of abundance of small and warm water species
(Capros aper, Microchirus variegatus, Dicologlossa
cuneata...) which are favoured by climate change
 Climate change is one of a long list of pressures that
influence the distribution and abundance of populations
 Decrease of trophic level of species group B can be
explained by increase of blue whiting abundance as hake
and whiting decrease. Climate change and fishing effect
favour lower trophic level species