According to researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, decades of intense fishing pressure didn’t just reduce the [cod] population – it rewired the species itself.

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“Selective overexploitation has altered the genome of Eastern Baltic cod,” explains Dr. Kwi Young Han, the study’s first author. “We see this in the significant decline in average size, which we could link to reduced growth rates.”

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They traced how cod growth patterns and genetic traits shifted across nearly three decades of fishing pressure.

The outcome? Cod that grew fast and large used to be common. Now, they’ve nearly vanished. The survivors are the ones that grow slower, mature smaller, and escape early capture.

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“When the largest individuals are consistently removed from the population over many years, smaller, faster-maturing fish gain an evolutionary advantage,” noted Dr. Thorsten Reusch, head of the Marine Ecology Research Division at GEOMAR.

“What we are observing is evolution in action, driven by human activity. This is scientifically fascinating, but ecologically deeply concerning.”

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