CLUPEA
When Atlantic herring first entered the brackish waters of the Baltic Sea, it was faced with an extreme challenge. The water here was far less saline than in the Atlantic, an environment where many marine fish struggle to survive. Yet the herring managed to adapt, spread, and become one of the most important species in the Baltic. How did it succeed? And what happens to herring as climate change reshapes the conditions in the sea?
Herring has long been of great importance to both the Baltic Sea ecosystem, Swedish fisheries and to our food supply. At the same time, there is still much we do not know about how the fish have adapted to different environments and how future changes may affect the stocks.
In recent years, researchers have mapped the genomes of thousands of herring from both the Baltic Sea and the Atlantic. The results reveal links between specific genes and the fish’s ability to adapt to different environments, for example, how they cope with low salinity, temperature changes, or varying light conditions.
The CLUPEA project takes the next step
The CLUPEA research project, led by researchers at Uppsala University, aims to understand what these genes actually do, and how genetic variation shapes the fish’s functions and adaptive capacity. By studying which genes are activated in different parts of the fish and testing the effects of specific genetic changes, the researchers can trace the link from DNA to how the fish functions in its environment.
The research focuses in particular on genes involved in:
- adaptation to the low salinity of the Baltic Sea
- differences between spring- and autumn-spawning populations
- tolerance to temperature variation
- metabolic regulation, such as differences in fat content between Baltic and Atlantic populations
- vision and adaptation to the Baltic light environment
This knowledge is important both for research and for the management of herring. As the climate changes, temperature and salinity in the Baltic Sea are also expected to shift, especially in key spawning areas. This may affect both survival and reproduction. By improving our understanding of the genetic basis of adaptation, CLUPEA can contribute to better long-term management of one of the Baltic Sea’s most important species.
CLUPEA at BalticWaters Fish Laboratory
Parts of the CLUPEA project are conducted in collaboration with BalticWaters Fish Laboratory. At the laboratory, researchers perform controlled in vitro-fertilisations and collect samples from embryos, newly hatched larvae, and adult fish. This creates new opportunities to study how gene activity affects development and survival, as well as differences between spring- and autumn-spawning populations.
The CLUPEA project – Unravelling molecular mechanisms behind adaptation to environmental heterogeneity and change – is conducted by researchers at Uppsala University. The project runs for five years starting in 2025 and is funded by the Knut and Alice Wallenberg Foundation.