New study reveals limited diet overlap among small pelagic fish in the Baltic Sea
Photo: Kinlan Jan
Small pelagic fish are central to the Baltic Sea food web. They feed on plankton and serve as prey for larger fish, seabirds and mammals. Because of this, their feeding habits influence the entire ecosystem. A new study led by researchers at the Department of Ecology, Environment and Plant Sciences (DEEP), published in ICES Journal of Marine Science, shows that the main pelagic fish species in the central Baltic, herring, sprat and stickleback, overlap surprisingly little in their use of resources.
Less overlap than expected
Group Winder at DEEP, together with colleagues at the Swedish University of Agriculture examined the diets of the dominant species by combining stomach content analyses with data on prey availability. Using DNA metabarcoding, they could assess the full spectrum of their resource use. Modest diet overlap was also supported by stable isotope data. The results suggest that these fishes are not locked in strong competition under current conditions. Seasonal dynamics in prey availability play a key role, as the fish adjust their diets throughout the year.
Sampling onboard R/V Svea in May 2022. Photo: Kinlan Jan
Implications for management
These findings suggest that the fish species have developed flexible feeding strategies, which may help stabilize the ecosystem. Lower competition means that populations are less likely to collapse if one type of prey becomes scarce. This knowledge is important for fisheries and ecosystem management, which often assume higher levels of competition than this study suggests.
A more resilient ecosystem
While the study is limited to the central Baltic Sea, the results provide a more optimistic view of the ecosystem’s resilience. By using resources differently, pelagic fishes reduce pressure on each other and create a buffer against environmental fluctuations. Future research will explore whether this pattern holds in other regions and under more extreme conditions.
Access the scientific article, published in ICES Journal of Marine Science on 9 September, here: Limited resource use overlaps among small pelagic fish species in the central Baltic Sea.
Last updated: 2025-12-05
Source: Department of Ecology, Environment and Plant Sciences