Overview

• The median length of mature Eastern Baltic cod dropped from 40 cm in 1996 to 20 cm in 2019, reflecting a 50% reduction under intense fishing pressure.
• Genetic analyses identified directional selection on growth-related genes and a chromosomal inversion linked to slower growth and earlier maturation.
• Researchers examined otoliths from 152 cod collected in the Bornholm Basin between 1996 and 2019 to reconstruct growth patterns and genomic change.
• A fishing ban imposed in 2019 has failed to produce any significant rebound in body size, indicating long-term evolutionary impacts.
• Scientists warn that the loss of genetic diversity may hinder the population’s ability to adapt to future environmental challenges and urge fisheries management to factor in evolutionary timescales.