climate, zooplankton and pelagic fish growth in the central baltic sea christian möllmann © georgs...

Climate, zooplankton and pelagic fish growth in the Central Baltic Sea

Christian Möllmann ©Georgs Kornilovs ®

Marina Fetter ®Friedrich W. Köster ©

© Danish Institute for Fisheries Research, Charlottenlund® Latvian Fisheries Research Institute, Riga

Ministry of Food, Agriculture and FisheriesDanish Institute for Fisheries Research

Stock development

herring

sprat

stoc

k si

ze (

num

ber

s)

0

2e+10

4e+10

6e+10

8e+10

wei

ght-

at-ag

e (k

g)

0.02

0.03

0.04

0.05

0.06

0.07

0.08stock size

weight- at- age

1980 1985 1990 1995 2000

0

1e+11

2e+11

3e+11

4e+11

5e+11

0.008

0.010

0.012

0.014

0.016

0.018

Condition*

herring

cond

itio

n (g

)

40

45

50

sprat

1980 1985 1990 1995 2000

cond

itio

n (g

)

25

30

35

*log-log regression;weight at mean length;spring

Aim(s)

• show effect of climate on Baltic hydrography• demonstrate effect of hydrography on dominating copepod species• evaluate if trends in copepods affect feeding of herring and sprat• relate trends in feeding to condition• explain growth changes ?

Time-series

• quarterly, 1977-2003• climate index (BSI)• hydrography (T, S & O2)• mesozooplankton abundance• herring & sprat stomach contents• herring & sprat length+weight• Gdansk Deep & Gotland Basin

Climate

1980 1985 1990 1995 2000

BSI

-6

-4

-2

0

2

4

6

8

BSI

Plot 2 Zero

Baltic Sea Index (BSI)

Climate & hydrography

BSI-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

deg

C

0.4

0.5

0.6

0.7

0.8

0.9

Temperature(O-50m)

r=0.60

BSI-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

psu

0.90

0.92

0.94

0.96

0.98

1.00

1.02

1.04

Salinity(50-100m)

r=0.62

Copepod community change

0%

25%

50%

75%

100%

Acartia

TemoraPseudocalanus

Acartia/Temora & temperature

1980 1985 1990 1995 2000stan

dar

diz

ed a

bun

dan

ce (

n*m

-2)

& t

empe

ratu

re 0

-50m

(deg

C)

-2

-1

0

1

2

3

Acartia

Temora

temperature

r = 0.69 (Acartia) – r = 0.79 (Temora)

Process behind Acartia/temperature

Eg

g p

rod

uct

ion

[eg

gs

fem

-1 d

-1]

Tem

per

atu

re

Hatch

ing

%

0

10

20

30

40

0 4 8 12 16 20 24 28 32 36 40

4 °C10 °C

Resting eggs vs. in-situ egg production

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9

0

20

40

60

80

100egg productiontemperaturehatching

month

Dutz et al., 2004

weeks

1980 1985 1990 1995 2000stan

dar

diz

ed a

bun

dan

ce (

n*m

-2)

& s

alin

ity

50-100m

(ps

u)& o

xyg

en (

ml*

l-1)

-2

-1

0

1

2

3Pseudocalanus

salinity

oxygen

Pseudocalanus & salinity(& oyxgen)

r = 0.46 (with 1993) – r = 0.69 (without 1993)

Process behind Pseudocalanus/salinity

Color scale – salinity [PSU]

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0- 9 0

- 8 0

- 7 0

- 6 0

- 5 0

- 4 0

- 3 0

- 2 0

- 1 0

67891 01 11 21 31 41 51 61 71 81 9

Schmidt et al., 2003

May 2002 (stagnation) April 2003 (post-inflow)

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0- 9 0

- 8 0

- 7 0

- 6 0

- 5 0

- 4 0

- 3 0

- 2 0

- 1 0

67891 01 11 21 31 41 51 61 71 81 9

Color scale – salinity [PSU]Black line – oxygen content [ml*l-1] Schmidt et al., 2003

Process behind Pseudocalanus/salinity

May 2002 (stagnation) April 2003 (post-inflow)

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0- 9 0

- 8 0

- 7 0

- 6 0

- 5 0

- 4 0

- 3 0

- 2 0

- 1 0

67891 01 11 21 31 41 51 61 71 81 9

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0

Color scale – salinity [PSU]Black line – oxygen content [ml*l-1]Red dots – individual egg-carrying females Schmidt et al., 2003

Process behind Pseudocalanus/salinity

May 2002 (stagnation) April 2003 (post-inflow)

Herring feeding

summer

1980 1985 1990 1995 2000

wet

wei

ght

(g)

0.00

0.04

0.08

0.12

0.16

0.20

other copepodsAcartiaTemora

Pseudocalanus

spring

wet

wei

ght

(g)

0.00

0.02

0.04

0.06

0.08

0.10

Condition - causes

log Pseudocalanus4.2 4.4 4.6 4.8 5.0

log

cond

itio

n

1.60

1.62

1.64

1.66

1.68

1.70

1.72

Herring - spring

r= 0.60

log sprat10.4 10.6 10.8 11.0 11.2 11.4 11.6 11.8

r = 0.71

spring

wet

wei

ght

(g)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

mean stomach contentcondition

summer

1980 1985 1990 1995 2000

wet

wei

ght

(g)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

Sprat feeding

other copepodsAcartiaTemoraPseudocalanus

cladocerans

77- 90 91- 0320

25

30

spring

summer

condition

77- 90 91- 03

500.0x103

1.0x106

1.5x106

2.0x106

2.5x106

plankton

77- 90 91- 03

100x109

200x109

300x109

sprat stock

Condition - causes

Sprat – spring & summer

Summary

• strong link between climate and hydrography• salinity and temperature changes determine copepod community• decrease in Pseudocalanus affected herring growth• no ”plankton effect” on sprat growth• strong competition due to large sprat stock• no direct effect of temperature & salinity