PhD students

Background of the project
Decreased frequencies of major inflow events of oxygenated water, together with increasing sea surface temperatures and immense anthropogenic pressures, have intensified the extent and severity of hypoxia in the Baltic Sea. These factors have in recent decades negatively affected key physiological and ecological parameters of cod (Gadus morhua) in this region. Notably however, recent reports from the Åland Sea in the northern Baltic have shown noticeably larger and healthier cod, compared to cod from the southwestern and central Baltic. The reasons for this difference have been hypothesized to be better oxygen conditions in these northerly areas, in addition to higher availability of Saduria entomon, a key prey item in the diet of cod which in recent times has decreased in the central parts of the Baltic. 

About the project
Combining controlled experiments with information derived from the field, the aim of this study is to investigate the physiological changes that occur when Baltic cod is exposed to prolonged moderate hypoxia. In addition, the project will include historical analysis of Saduria distributions coupled to environmental data of oxygen conditions across the Baltic, and stomach content analysis of the Åland cod, to test the hypothesis of Saduria as a key determinant of the health status of the Baltic cod. 

Perspectives
Findings from this study will provide important insights for fisheries management and conservation efforts in the Baltic. Understanding the link between environmental stressors, such as hypoxia, and food quality can inform strategies to protect and restore Baltic cod populations. Moreover, recognizing the importance of Saduria as essential prey could lead targeted efforts to preserve or its populations in the central Baltic, potentially improving the resilience of Baltic cod.

Supervisors
Jane W. Behrens, Mikael van Deurs and Kim Birnie-Gauvin, DTU Aqua