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Eastern Baltic cod has evolved to be smaller and slip through nets, according to historical research that overfishing with changes in the DNA of the marine species connects.
Cod that would ever have overshadowed a plate now fits easily on one because faster -growing specimens that are usually caught for food largely disappeared, scientists have discovered.
The evolutionary shifts powered by human over -exploitation risks that undermine some fish populations that are irreparable, according to researchers who watched fish -DNA for almost a quarter of a century.
“For the first time in a full marine species, we provided evidence of evolutionary changes in the taken of a fish population that is subject to intense exploitation, which the population has pushed on the edge of collapse,” said Kwi Young Han, main author of the research published in the Journal Science Advances on Wednesday.
Just over a third of the world’s marine fish that are usually caught on human consumption, is considered overfish, according to the Food and Agricultural Organization of the UN. The median adult length of Eastern Baltic cod has been halved since the 1990s from 40 cm to around 20 cm, published according to research last year.
Fishing on Eastern Baltic Cod Is banned By the EU since 2019, after a steep fall in the population of the species.
Han and her colleague researchers analyzed genetically and chemically small earnings in 152 cod caught from 1996 to 2019 in the Bornholm pelvis between Sweden and Poland. Faster growing specimens almost disappeared, while fish that slowly grew but achieved reproductive adulthood with a smaller size.
The researchers found proof of so -called directional selection in the evolution of genetic variants associated with body growth. This meant that the slower -growing fish gradually occurred more often and the faster -growing specimens less.
The authors of the study had “broken new terrain” when linking shrinking fish sizes “genes that are important for fish growth and reproduction,” said Malin Pinsky, a marine biologist who studied Atlantic COD.
While fish had evolved to survive, the genomic changes created many problems, Pinsky said. Smaller fish produce fewer offspring, while the genetic narrowing of the species harms its potential to adapt to changes in the environment. Smaller fish were more vulnerable to predators and climate change, he said.
“We are worried about these populations and others as they collapse or even extinct.”
Similar evolutionary shifts have appeared in species, including atlantic salmon and have probably influenced other heavily exploited marine fish, such as anchovies, herring and tuna, said Han, who did the research in Geomar Helmholtz Center for Ocean Research Kiel in Germany.
The study produced important genetic evidence of the evolutionary selection pressure exerted by fishing, said Rick Stafford, professor of Marine Biology at Bournemouth University.
“COD can live more than 30 years, but with the current visits it is rare to find COD more than five years old,” said Stafford.
