The impact of Climatic Changes on the Adaptation of Marine Fish in the

Baltic Sea

Evald Ojaveer

Estonian Marine Institute of the University of Tartu

Margers Kalejs

Georga Apina 22-8, Valmiera 4201, Latvia

Structure

• Freshened Baltic water• Halocline• Modified saline water

A chain of basins separated by • topographic (coasts, islands, bottom relief),• or hydrological (fronts) constraints

• SW and shallower parts -- boreal character• NW and deeper parts -- arctic

Climate water masses inflows

SW Atlantic saline frequent E Continental Typical Baltic strong,moderate NW Atlantic/arctic Freshened only very strong

Main environmental conditions

Area Salinity Ice (%) Temperature Spr.bloom

Kattegat 12-30/32-34 20 17/2 II-III

Belts,Sound 8-17/16-23 30 17/2 III

Arkona 7.5-10/10-23 5 17/2 III-IV

Bornholm 7-8.5/14-21 0 17/2 IV

Gotland 8/11-14 10 16.5/2 IV-V

NW 7/9-12 40 16.5/1 IV-V

GofRiga 5-7 100 18-19/0 IV-V

GofFinland4.5-7/6-10 100 16/0-0.5 IV-V

Bothn. Sea 6-7 100 14-19/0 IV-V

Bothn. Bay 3-4.5 100 13-17/0 VI

SW E NW GoF GoR GOB

Spr. herring + + + + + +

Sandeel + + + + + +

Stickleback + + + + + +

Flounder + + + + + (+)

Sprat + + + + (+)

Cod + (+) (+)

Rockling + (+)

Plaice + (+)?

Dab +

Adaptations

• Higher fecundity

• Earlier maturation

• Lower specific gravity of eggs

• Longer spawning period

• Survival of deviated individuals

Hydrographic conditions/year-class abundance

Hydrographic conditions/year-class abundance

Influence of higher salinity and mild winters

Increase in population abundance

Extension of the area

Influence of stagnation,decrease of salinity in deeps, negative temperature anomaly in winter

• Weakening of immigration

• Strong natural selection for elimination of less adapted phenotypes

Anthropogenic impacts

• Increase of production in pelagic layers• Oxygen depletion in deep layers• Exploitation, especially overexploitation decreases

abundance, possibly also genetic variation• Introduction of alien species has controversial

influence

Species of marine origin adapted in all regions of the Baltic Sea

• Clupea harengus membras -- 10-12 major populations

• Ammodytes tobianus -- probable several populations

• Pomatoschistus minutus• Zoarces viviparus -- probably several populations• Triglopsis quadricornis -- probably several

populations• Myoxocephalus scorpius

Species adapted in the Baltic Proper

• Platichthys flesus trachurus -- probably 6-7 local populations

• Gadus morhua callarias -- 2 populations• Rhinonemus cimbrius• Sprattus sprattus balticus• Autumn spawning herring --several

subpopulations

Species adapted in the SW part of the sea

• Pleuronectes platessa• Limanda limanda -- probably 2 populations

Possible next important natural immigrant

• Mackerel Scomber scombrus