Phenotypic and genomic variation within the eastern Baltic cod population

The Atlantic cod is the main top fish predator in the pelagic of the Baltic sea and of huge ecological and economic value. However, the situation of the eastern cod stock occurring in the Baltic proper is dire.

Due to overfishing, poor growth of individual fish and recruitment failure the stock is at its all-time low and since 2019 the cod fishery is closed.

Intriguingly, the fish in the Åland sea are still large and in good condition, and a large proportion of the fish is in spawning condition.

Recent preliminary studies show the sperm are motile and the eggs can hatch at lower salinities than those of the fish from the southern Baltic proper.

In this project, we will focus on the adaptive potential of Baltic cod in relation to changing conditions in the Baltic sea.

In the laboratory, we will compare key early life history parameters including sperm motility, egg buoyancy and hatching success and larval survival in a range of salinities between northern and southern Baltic proper cod.

We will conduct a factorial experiment with salinity and temperature to investigate the adaptive potential of cod to future conditions in the Baltic sea.

These experiments will be combined with transcriptomic and epigenomic analyses to investigate the physiological and genetic mechanisms behind the adaptive divergence in response to environmental conditions.

These analyses will give a detailed picture on the adaptive potential within the eastern cod population in the Baltic proper.