1. 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 Fisheries Danish Institute for Fisheries Research

2. Stock development herring sprat

3. Condition* *log-log regression; weight at mean length; spring

4. 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 ?

5. Time-series quarterly, 1977-2003 climate index (BSI) hydrography (T, S & O 2 ) mesozooplankton abundance herring & sprat stomach contents herring & sprat length+weight Gdansk Deep & Gotland Basin

6. Climate Baltic Sea Index (BSI)

7. Climate & hydrography Temperature (O-50m) r=0.60 Salinity (50-100m) r=0.62

8. Copepod community change Acartia Temora Pseudocalanus

9. Acartia/Temora & temperature r = 0.69 (Acartia) – r = 0.79 (Temora)

10. Process behind Acartia/temperature Egg production [eggs fem -1 d -1 ] Temperature Hatching % Resting eggs vs. in-situ egg production month Dutz et al., 2004 weeks

11. Pseudocalanus & salinity (& oyxgen) r = 0.46 (with 1993) – r = 0.69 (without 1993)

12. Process behind Pseudocalanus/salinity Color scale – salinity [PSU] Schmidt et al., 2003 May 2002 (stagnation) April 2003 (post-inflow)

13. 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)

14. 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)

15. Herring feeding other copepods Acartia Temora Pseudocalanus

16. Condition - causes Herring - spring r= 0.60 r = 0.71

17. mean stomach content condition Sprat feeding other copepods Acartia Temora Pseudocalanus cladocerans

18. condition planktonsprat stock Condition - causes Sprat – spring & summer

19. 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