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Variation in fish condition within and between populations: the effect on their productivity and management implications (Mediterranean and North Atlantic)
Josep Lloret(a) , Hans-Joachim Rätz(b) and Montserrat Demestre (a)
(a) Institut de Ciències del Mar (CMIMA-CSIC), Barcelona, Catalonia, Spain
(b) Institut für Seefischerei, Hamburg, Germany
UNESCO WORKSHOP June 2005. Varna (Bulgaria)
LARGE-SCALE DISTURBANCES (REGIME SHIFTS) AND RECOVERY IN AQUATIC
ECOSYSTEMS: CHALLENGES FOR MANAGEMENT TOWARDS SUSTAINABILITY
1. Condition (fitness) is an important feature of fishes because it affects growth, reproduction and mortality
2. Two areas: Mediterranean and North Atlantic3. Several commercial demersal species: cod, white seabream,
hake, red mullet, etc4. Several sampling methods: groundfish surveys, data from fishery vessels, spear fishing5. Several condition indices: K, HSI, DSI, GSI, total lipids
(muscle and liver)6. Publications:
2005. H.J. Rätz and J. Lloret. ICES Journal of Marine Science (in press). 2005. J. Lloret, R. Galzin, L. Gil de Sola, A. Souplet and M. Demestre. Journal of
Fish Biology 67:1 (July; in press).2003. J. Lloret and S. Planes. Marine Ecology Progress Series 248:197-2082003. H.J. Rätz, J. Lloret. Fisheries Research 60:369-380.2002. J. Lloret, Gil de Sola, L., Souplet, A. and Galzin, R. ICES J. mar. Sci. 59:1215-
1227.
FISH CONDITION
MEDITERRANEAN
a) Condition is generally better in the north (Gulf of Lions: higher productivity) than in the south (Catalan Sea: lower productivity)
b) Condition generally decreases with depth (deep waters: lower productivity)
Rhône river
Ebre river
(230)
(38)
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
ln % lipiddry weight
Gulf of Lions Catalan Sea
Total lipids in the muscle of Pagellus acarne
MEDITERRANEAN
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
0 50 100 150 200 250 300Depth (m)
Ln
% li
pid
dry
wei
ght
Total lipids in the muscle of Mullus surmuletus
MEDITERRANEAN
Interannual fluctuations of K of Lophius piscatorius
B
1.1
1.2
1.3
1.4
1.5
1994 1995 1996 1997 1998 1999 2000 2001
Co
nd
itio
n fa
cto
r (K
)
MEDITERRANEAN
(84)
(84)
(46)
(46)
0
1
2
3
4
5
Muscle lipid Liver lipid
Rocky unprotectedSandy unprotected
Condition of juvenile Diplodus sargus is better in the rocky coast than in the sandy coast
% dry weight
MEDITERRANEAN
(19)
(19)(41)
(41)
0
0.5
1
1.5
2
HSI Muscle lipid
Rocky protected BanyulsRocky unprotected
Condition of post-spawners D. sargus is better in the rocky protected area of Banyuls than in the adjacent
rocky unprotected area
Index (HSI) or% dry weight
MEDITERRANEAN
(43)
(32)
(32)
(42)
0
2
3
Muscle lipid Liver lipid
Rocky Protected Cap CreusRocky unprotected
…and the same in the rocky protected area of Cap de Creus
% dry weight
1
4
MEDITERRANEAN
Greenland
Iceland
N W S cotland and Ireland
Irish S ea
S outhern G rand B ank
S G ulf o f S t. Law rence
Northwest
Greenland
Labrador
Grand Bank
Golf v. St. Lawrence
Georges Bank
NORTH ATLANTIC
Northeast
Northeast Arctic
Iceland
West of Scotland
North Sea
Irish Sea
SPATIAL VARIABILIY IN TEMPERATURE AND CONDITION
0.8
0.9
1.0
1.1
1.2
0 1 2 3 4 5 6 7 8 9 10 11
Temperature (°C)
Fu
lto
n's
co
nd
itio
n
GB
NS
IC
SLNO
SBGR
NE
SC
IR
r2=0,67, p=0,0036.
NORTH ATLANTIC
Cod stocks living in temperate waters are better conditioned than those living in cold waters
R2=0.28 Mean K= 0.89
0,8
0,85
0,9
0,95
1
1982 1984 1986 1988 1990 1992 1994 1996 1998
K
2
3
4
5
6
Tem
per
atu
re (
°C)
Condition factor (K) Temperature
INTERANNUAL VARIABILIY IN TEMPERATURE AND CONDITION IN GREENLAND
NORTH ATLANTIC
Condition is better when water temperature is higher than average
NORTH ATLANTIC
The strong year class 1984 of cod off Greenland experienced a low condition during the following years
-0,1-0,08-0,06-0,04-0,02
00,020,040,060,08
0,1
19751977197919811983198519871989199119931995199719992001
lnK
n
0
50000
100000
150000
200000
250000
ye
ar
cla
ss
e a
ge
3 (
mil
l)
mean lnKnyear class numbers at age 3
0
1
2
3
4
5
6
HSI M. barbatus DSI M. barbatus
Juveniles Adult males Adult females
HSI P. erythrinus
Sex differences in condition
Females are better conditioned than males; and adults better than juveniles
MEDITERRANEAN
Differences in condition between different reproductive stages of D. sargus (Gulf of Lions)
Post-spawners are better conditioned than spawners
(65)
(19)
0
2
4
6
8
10
12
DSI
Inde
x
Spawning males Post-spawning males
MEDITERRANEAN
HSI of cod during resting (Greenland, autumn 1998; males + females)
0
4
8
12
16
20
20 30 40 50 60 70 80 90 100Length (cm)
HS
I
Observed
Estimated
The bigger are better conditioned
NORTH ATLANTIC
GSI of Mullus barbatus during spawning (NW Mediterranean; spring 2000&2001; females)
5
10
15
20
10 15 20 25 30
Length (cm)
GS
I
MEDITERRANEAN
The bigger are better conditioned
GSI of Diplodus sargus during spawning (Gulf of Lions; spring 2001; males)
0
2
4
6
8
10
12
14
16
15 20 25 30 35 40
Length (cm)
GS
I
MEDITERRANEAN
The bigger are better conditioned
CONSEQUENCES OF THE VARIABILITY IN CONDITION:
EFFECTS ON STOCK PRODUCTIVITY AND
MANAGEMENT IMPLICATIONS
Growth of cod (weight at age 4)
0
1
2
3
4
5
6
0.8 0.9 1.0 1.1 1.2
Fulton's condition
We
igh
t a
t a
ge
4 (
kg)
IRSC
GB
NS
IC
GR
NE
SB
NO SLr2=0,79, p=0,0006.
Well conditioned cod stocks are more productive because they grow faster
NORTH ATLANTIC
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.8 0.9 1.0 1.1 1.2
Fulton's condition
Ric
ker'
s a
co
eff
icie
nt
IC
SC
SLNE
GR
SB
NO
NS
IR
GB
r2=0,49, p=0,0234.
Well conditioned cod stocks are more productive because they recruit more successful at decreased stock sizes
Recruitment potential of cod (Ricker’s a-coefficient from the SSB-R relationships)
NORTH ATLANTIC
40
45
50
55
60
1989 1991 1993 1995 1997 1999 2001 2003
len
gth
at
age
4
Growth of cod off Greenland is faster when condition is better; r2= 0.50
NORTH ATLANTIC
1. Poor conditioned populations are more susceptible to overexploitation
2. Low condition values recorded in given years can precede negative events in stock productivity in the following years: condition can be monitored to detect regime shifts and forecast changes in the productivity of stocks
3. Additional management measures are needed when poor condition values are recorded (in given years or habitats) In this sense, the protection of habitats can help to preserve the condition and status of fish stocks.
NORTH ATLANTICMEDITERRANEAN
TAKE CARE WITH POOR CONDITIONED FISH!