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

CAUSESOF VARIABILITY IN FISH

CONDITION

Habitat productivity

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

K of Lophius budegassaMEDITERRANEAN

DSI of Pagellus acarneMEDITERRANEAN

(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

Bottom characteristics

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

Habitat protection

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

Water temperature

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

GREENLAND

East Greenland

West Greenland

NORTH ATLANTIC

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

Stock density

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

Sex and reproductive stage

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

Size (age) of fish

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

Stock productivity

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

Management implications

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!