This large herring population has evolved uniquely over hundreds or thousands of years in the Baltic Sea.

Notably, these herring exhibit higher fat content and lower levels of dioxin, indicating a healthier profile for human consumption.

Analysis of the herring's morphology revealed damaged gill rakers, suggesting a significant dietary shift from plankton to fish, likely including the common stickleback.

Herring play a crucial role in the ecosystem, linking plankton production to various organisms, including predatory fish, seabirds, and humans.

The investigation into this unique herring began when local fishermen reported a larger type of herring that spawns just before midsummer.

A recent study from Uppsala University has identified genetically distinct, fish-eating herring in the Baltic Sea, a body of water that formed around 8,000 years ago following the last glaciation.

Genetic analysis revealed at least two distinct subpopulations of these fish-eating herring, located to the north and south of Stockholm.

The fish-eating herring's faster growth rates and reduced pollution risks further enhance their potential benefits for human consumption.

As keystone species, both Atlantic and Baltic herring are essential for connecting lower trophic levels like plankton to higher predators.

The evolution of these fish-eating herring is thought to be influenced by minimal competition from larger predatory fish, such as mackerel and tuna, which are absent in the Baltic Sea.

Historically, Baltic herring were classified as a subspecies of Atlantic herring, noted for their smaller size and lower fat content.

Previous research has highlighted various herring ecotypes that have adapted genetically to factors such as climate, salinity, and spawning seasons.