Post on 13-Jan-2016
Weever fish
What the non-commercially exploited species can tell us about climate change
Richard D.M. Nash1, Audrey J.Geffen1,2 & Henk Heessen3
1. Port Erin Marine Laboratory, University of Liverpool, Isle of Man, British Isles2. Department of Biology, University of Bergen, Norway3 Netherlands Institute for Fisheries Research, IJmuiden, The Netherlands
Why have an interest in non-commercial species?
However, changes in population size may be a consequence of fishing operations due to changes in habitat, ecosystem status and/or predator/prey relationships.
Therefore one cannot just choose any species if one wants to try and look at possible effects of climate change on fish populations and areas.
Changes in population size are not directly driven by commercial fishing.
The potential players
et al.
1965 1970 1975 1980 1985 1990 1995 2000Year
0
2
4
6
Ab
un
dan
ce in
dex
9
9.5
10
10.5
11
11.5
12
Te
mp
era
ture
(oC
)
Dutch coastal data
Solenette
1965 1970 1975 1980 1985 1990 1995 2000Year
0
1
2
3
4
5
Ab
un
dan
ce in
dex
9
9.5
10
10.5
11
11.5
12
Te
mp
era
ture
(oC
)
Dutch coastal data
Scaldfish
Why the interest?
Lesser weever: Echiichthys vipera
- 2 0 - 1 0 0 1 0 2 0 3 0
4 0
5 0
6 0
7 0
Distribution of Lesser Weever
Azores
Canaries
Lesser Weever
Classed as sub-tropicalNot commercially exploitedVery few predators
Generally found on soft substrata BuriesSpawns June to AugustJuveniles tend to be inshore and larger adults further offshoreTends to inhabit areas <50m depth
Wheeler, A. 1978. Key to the Fishes of Northern Europe.
It has no value to fishermen or anglers, and its chief impact on man is in being one of very few dangerous fishes in European seas.
Totenese, E. 1986. CLOFNAM.
This species is considered the most dangerous of the European weevers, both for its poison and for its frequent occurrence very near to beaches.
North Sea
1. Annual changes in lesser weever distribution
2. Annual changes in lesser weever abundance
3. Changes in lesser weever length frequencies
0 5 10
50
55
60
1971
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1972
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1973
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1974
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1975
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1976
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1977
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1978
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1979
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1980
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1981
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1982
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1983
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1984
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1985
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1986
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1987
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1988
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1989
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1990
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1991
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1992
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1993
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1994
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1995
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1996
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1997
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1998
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
1999
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
0 5 10
50
55
60
2000
North Sea weever fish (Catch per rectangle)
0 to 1
1 to 10
10 to 50
50 to 100
100 to 500
1970 1975 1980 1985 1990 1995 2000
0
10
20
30
40
50
M
ean
ab
un
dan
ce
per
sam
ple
d r
ecta
ng
le
0
5
10
15
20
25
30
No
of
rect
ang
les
con
tain
ing
wee
vers
North Sea
IBTS
1970 1975 1980 1985 1990 1995 2000 2005
0
4
8
12
16
20
Ab
un
dan
ce (
no
. ha-1
)
North SeaDutch surveys
0 5 1 0
5 0
5 5
6 0
1970 1975 1980 1985 1990 1995 2000Year
Lesser Weever: Latitude of population centre
0
2000
4000
0
2000
4000
0
2000
4000Ab
un
dan
ce
4 8 12 16Total length (cm )
0
2000
4000
1985-89
1990-94
1995-99
2000-03
Irish Sea
1. Distribution of lesser weever
2. Annual changes in population size of lesser weever
3. Annual variation in production of lesser weever
4. Changes in condition of lesser weever
Distribution of Lesser Weever in the Irish Sea
- 6 - 5 - 4 - 35 3
5 4
5 5
1 9 9 4
-6 -5 -4 -353
54
55
ENGLANDIRELAND
W ALES
SCOTLAND
IoM
Liverpool Bay
Simulated drift of plaice eggs and larvae, in the Irish Sea, after 31 and 61 days. Vertical movement behaviour patterns allowed for larvae. Data based on distribution of eggs and current patterns in 1995.Data from DEFRA/CEFAS funded research (MF0425) - plaice
Juvenile lesser weever (and plaice) and nursery grounds in the eastern Irish Sea
- 6 - 5 - 4 - 3
53
54
55
1 2
3
4
56
7
W ales
England
Scotland
Ireland
IrishSea
Zone 1Red Wharf Bay andPenmaenmawr
Zone 3Blackpool andMorecambe
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year
0
10
20
30P
op
ula
tio
n s
ize
(mill
ion
s)
9 . 6
1 0
1 0 . 4
1 0 . 8
1 1 . 2
1 1 . 6
Mea
n a
nn
ual
te
mp
erat
ure
(o
C)
Lesser W eever fish in the Irish Sea
Survey data supplied by CEFAS, Lowestoft
Incom plete surveys
Lesser weevers in the Irish Sea (temperature 4 years ahead of population size)
R sq = 0.73
9 . 6 9 . 8 1 0 . 0 1 0 . 2 1 0 . 4 1 0 . 6 1 0 . 8 1 1 . 0 1 1 . 2 1 1 . 4 1 1 . 6M ean Annual tem perature (oC)
0
5
10
15
20
25
30
Po
pu
lati
on
siz
e (m
illi
on
s)
19901991
1992
1993
1994
1995
1996
1997
19981999
2000
Lesser weevers in the Irish Sea (temperature 4 years ahead of population size)
R sq = 0.73
9 . 6 9 . 8 1 0 . 0 1 0 . 2 1 0 . 4 1 0 . 6 1 0 . 8 1 1 . 0 1 1 . 2 1 1 . 4 1 1 . 6M ean Annual tem perature (oC)
0
5
10
15
20
25
30
Po
pu
lati
on
siz
e (m
illi
on
s)
19901991
1992
1993
1994
1995
1996
1997
19981999
2000
2001
2002
2003
- 6 - 5 - 4 - 3
5 3
5 4
5 5
I R I S H S E A
L e s s e r w e e v e r : L a t i t u d e o f p o p u l a t i o n c e n t r e
1988 1990 1992 1994 1996 1998 2000 2002 2004Year
53
54
Lat
titu
de
(N)
1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year
0
10
20
30
Po
pu
lati
on
siz
e (m
illio
ns)
5 3
5 3 . 5
5 4
Lat
itu
de
of
po
pu
lati
on
cen
tre
Lesser W eever fish in the Irish Sea
Survey data supplied by CEFAS, Lowestoft
Incom plete surveys
92-93 93-94 94-95 95-96 96-97 97-98 98-99 99-00 00-01 01-02
Years
0
100
200
300
An
nu
al P
rod
uct
ion
(g
wet
wei
gh
t p
er 1
00 in
div
idu
als)
0
200
400
600
800
1000
To
tal A
nn
ual
Pro
du
ctio
n
(to
nn
es)
1 0
1 0 . 4
1 0 . 8
1 1 . 2
1 1 . 6
Me
an
An
nu
al
tem
pe
ratu
re (
oC
)
4 8 12 16 20 24 28Population size (millions)
0.96
1
1.04
1.08
1.12
1.16
Mea
n c
on
dit
ion
Fac
tor
(K)
1992
1993
1994
1995
1996
1997
1998
1999
2000
20012002
1 0 1 0 . 4 1 0 . 8 1 1 . 2 1 1 . 6Mean Annual Temperature (oC)
0.96
1
1.04
1.08
1.12
1.16
Mea
n c
on
dit
ion
Fac
tor
(K)
1992
1993
1994
1995
1996
1997
1998
1999
2000
20012002
One final thought
1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year
0
10
20
30
Po
pu
lati
on
siz
e (m
illio
ns)
0
4000
8000
12000
16000
Sp
awn
ing
Sto
ck B
iom
ass
(t)
Co
d
Lesser W eever fish in the Irish Sea
Survey data supplied by CEFAS, Lowestoft
Incom plete surveys
1970 1975 1980 1985 1990 1995 2000 2005
0
10
20
30
40
50
M
ean
ab
un
dan
ce
per
sam
ple
d r
ecta
ng
le
0
50000
100000
150000
200000
250000
300000
Sp
awn
ing
Sto
ck B
iom
ass
of
Co
d
North Sea
In both areas there has been a decline in e.g. cod stocks.In both areas there has been a general increase in water temperatureIn both areas the lesser weever population appears larger than in the immediate past.
What can non-commercially exploited species tell us about climate change?
Even these species are subjected to variability driven by commercial fishing operations – difficult to disentangle climate versus other driving factors.
In many cases the data time series are too short to show clear trends in distribution, however, there are signs of increased population size of e.g. weever fish in to the North Sea.
In the case of the Irish Sea population there was a clear trend in population size with the thermal regime, however, this breaks down in more recent years.