Saving Seafood

These Cod Have Been Shrinking Dramatically for Decades. Now, Scientists Say They’ve Solved the Mystery

July 7, 2025 — A new study reveals that decades of overfishing have altered the evolution of cod in the eastern Baltic Sea.

The research, published in the journal Science Advances on June 25, aimed to answer a question that had puzzled scientists for decades: What’s behind the dramatic size change in eastern Baltic cod?

These fish used to be enormous. In 1996, the biggest Baltic cod grew more than three feet long. By 2019, however, their sizes had been cut in half, and the cod’s weight was but a fraction of its previous glory. Now, the average cod can sit in a person’s cupped hands.

For decades, fishers in the Baltic Sea caught cod relentlessly, using large nets. Smaller fish could escape more easily, presenting an external pressure to remain smaller. But directly connecting the population’s decrease in size to evolution—and not other environmental factors, such as pollution or temperature change—is notoriously difficult for scientists.

Regulators banned fishing of eastern Baltic cod in 2019 due to a population collapse, but their size still shows no signs of bouncing back. In the new study, scientists find that overfishing did not merely remove the biggest individuals—it changed the genetic composition of the cod population, predisposing them to remain small.

“Human harvesting elicits the strongest selection pressures in nature,” Thorsten Reusch, a marine ecologist at the GEOMAR Helmholtz Center for Ocean Research Kiel in Germany and co-author of the paper, tells Emily Anthes of the New York Times. “It can be really fast that you see evolutionary change.”

Read the full article at The Smithsonian Magazine

Brussels enacts emergency ban to protect Baltic cod

July 24, 2019 — Emergency measures to save the ailing eastern Baltic cod stock from impending collapse have been announced by the European Commission. With immediate effect, commercial fishing for cod is banned in most of the Baltic Sea until 31 December, 2019.

The ban covers all fishing vessels and applies in all those areas of the Baltic Sea where the largest part of the stock is present, namely subdivisions 24-26, except for some specific targeted derogations.

It follows measures that have already been taken by some European Union member states, but given that these measures have not ensured a uniform approach in all areas where the eastern Baltic cod stock is found, and that not all member states intended to adopt national measures, the Commission decided that further emergency action was warranted.

“The impact of this cod stock collapsing would be catastrophic for the livelihoods of many fishermen and coastal communities all around the Baltic Sea. We must urgently act to rebuild the stock – in the interest of fish and fishermen alike. That means responding rapidly to an immediate threat now, through the emergency measures the commission is taking. But it also means managing the stock – and the habitat it lives in – properly in the long term,” E.U. Commissioner for Environment, Maritime Affairs, and Fisheries Karmenu Vella.

Read the full story at Seafood Source

Baltic Cod Fishermen Get Better Quotas Than Science Wants

October 11th, 2016 — With Baltic cod drawing closer to the edge of commercial extinction, the European Union on Monday set tougher catch quotas for fishermen but stayed well above targets sought by scientists and environmentalists.

After all-day negotiations in Luxembourg, the EU fisheries ministers agreed on a 56 percent quota cut for the western Baltic cod caught off Denmark and Germany, while scientists were pushing for the quota to be cut by about 90 percent.

Officials said Denmark was pushing hard to safeguard the livelihood of its fishermen to make sure there was enough that they would still be allowed to catch.

EU Fisheries Commissioner Karmenu Vella had been seeking a reduction of 88 percent “to bring back the stock to sustainability as soon as possible” but also had to compromise to keep member states on board for a unanimous decision.

“After listening to the member states’ arguments, and the impacts on the different fleets and in particular on artisanal fleets, I have accepted a lower reduction,” Vella said, insisting it would still give the species a good chance of survival in the Baltic waters.

The EU has agreed to revamp its fishing policies to protect dozens of species from commercial extinction, and by 2020 all fish must be sustainably caught. Member states, however, have a long tradition of rejecting scientific advice and instead sought the best deal possible for the industry, not for the survival of the fish. Over the years, it has driven many species to the edge of a full collapse, and instead of being plentiful, like cod in the Atlantic and North Sea and Bluefin tuna in the Mediterranean, they became threatened species.

It is now the same for cod in the western Baltic and tough quota reductions are needed. Some environmentalists have called for a total closing of those fisheries.

Read the full story at The New York Times