At a Glance
- Norwegian spring-spawning herring have shifted their spawning grounds 800 kilometers northward, moving from southern Norway to Lofoten due to a breakdown in intergenerational learning.
- This shift is attributed to the loss of older fish caused by age-selective fishing, disrupting the social learning process known as entrainment that once guided younger herring.
- Researchers used long-term fisheries data, acoustic surveys, and tagging experiments to track the emergence of a new dominant migration route beginning with the 2016 herring cohort.
- By 2021, most herring followed the northern route, reinforcing the new behavior in the absence of older fish capable of transmitting traditional migration knowledge.
- The study warns that fishing practices can alter natural behaviors in marine species, potentially creating irreversible ecological shifts with widespread effects on local food webs and fisheries.
A recent study has shown that Norwegian spring-spawning herring (NSS herring) has shifted its spawning grounds by 800 kilometers, moving from Norway’s traditional southern coast to the northern Lofoten region. This surprising change in migration routes is linked to the loss of collective memory, which is passed down through generations of fish, particularly from older, experienced herring to younger recruits. The study, led by the Institute of Marine Research in Norway, suggests that this disruption may have significant consequences for local ecosystems and fisheries.
The migration behavior of NSS herring has long been an example of how schooling fish pass on their migration routes through social learning, a process known as “entrainment.” Having followed the same migration paths for years, older herring helps guide younger fish to appropriate spawning areas. However, the study found that a reduction in the population of older herring, caused by age-selective fishing, resulted in fewer opportunities for young fish to learn from experienced ones. This loss of guidance led to a shift in migration patterns, with younger herring now opting for a northern route to Lofoten.
Using extensive data from fisheries records, acoustic surveys, and tagging experiments, the research team tracked the movement of herring over several years. They observed that the 2016 cohort of herring began to use the northern migration route, bypassing the traditional southern spawning grounds. By 2021, this northern route had become the dominant migration pattern as the younger fish continued reinforcing this behavior. The study also noted a significant decline in the population of older fish, which further diminished the potential for cultural transmission of migration knowledge.
The findings, published in Nature, highlight the impact that fishing practices and environmental changes can have on species’ natural behaviors. In this case, the loss of older herring has led to a new migration pattern, with possible long-term effects on the local food web. As these new migration routes become more established, reversing the change may prove difficult, and the implications for the fish population and the surrounding ecosystem are still being explored.
References
- Jackson, J. & Phys.org. (2025, May 13). Collective memory loss in herring results in 800 km shift in spawning grounds. Phys.Org; Phys.org. https://phys.org/news/2025-05-memory-loss-herring-results-km.html
- Slotte, A., Salthaug, A., Vatnehol, S., Johnsen, E., Mousing, E. A., Høines, Å., Broms, C. T., Bjarnason, S., Homrum, E. Í., Skagseth, Ø., & Stenevik, E. K. (2025). Herring spawned poleward following fishery-induced collective memory loss. Nature. https://doi.org/10.1038/s41586-025-08983-3
