What over-fishing has done to the size of cod in just 30 years

Environment
26 Jun 2025 • 11:03 PM MYT
The Independent
The Independent

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  • Excessive fishing has caused Baltic cod to undergo genetic changes, halving their size over the past 30 years.
  • A study published in Science Advances is the first to demonstrate that decades of overfishing and environmental changes can profoundly alter the genetic makeup of a fully marine species.
  • Researchers found a 48 per cent decrease in the asymptotic body length of Eastern Baltic cod between 1996 and 2019, with genetic variations indicating evolution driven by human interference.
  • The study revealed that the genomes of fast-growing cod systematically differed from slow growers, with fast-growing individuals nearly disappearing from the Baltic Sea.
  • This phenomenon is described as evolution in action driven by human activity, where the consistent removal of larger fish gives smaller, faster-maturing fish an evolutionary advantage.

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