Overfishing changes not only stocks but also the genome of cod in the central Baltic Sea. A new study from GEOMAR shows: The animals grow slower today and remain smaller – a consequence of decades of fishing.

 

Genetic changes due to fishing pressure

Researchers identified gene variants associated with growth that have changed due to selective fishing. A chromosomal inversion was also affected.

 

Otoliths provide a time travel

Using ear stones (otoliths) from 152 cod from the years 1996–2019, the researchers demonstrated how growth and genetics have changed.

 

Slow-growing cod survive

Smaller cod that reproduce earlier had a survival advantage. Large, fast-growing specimens almost completely disappeared.

 

Recovery hardly possible

Genetic diversity shrank, recovery remains absent – despite a fishing ban since 2019.

 

Conclusion

Fishing influences evolution. Sustainability must be thought of in the long term.