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Selective Fishing Halves Eastern Baltic Cod Size and Reshapes Their Genomes

Using otolith archives paired with DNA sequencing, the study reveals evolutionary shifts that have prevented cod from regaining lost growth since 2019

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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.