Cod stocks in the western Baltic Sea are at an historic low. If fishing continues, they could collapse to such an extent that they are irretrievably lost - if not biologically, then at least for the 400 German commercial fishers whose livelihoods depend, among other things, on these animals.
Unfortunately, this would not be the first time that humans have depleted the sea of a fish stock: this has already occurred once before, during the Middle Ages.
A particularly extensive study from Kiel has reconstructed catch figures between 1200 and 1600. Even then, long before industrialisation, a combination of overfishing and external environmental influences drove the stock decline. Around 1500, the average temperature dropped by 0.85°C due to a cold period, meaning that the autumn-spawning herring, a major food source for the flourishing Hanseatic League at the time, no longer produced enough young to survive the winter. Stocks rapidly collapsed, destroying the livelihoods of thousands of fishers. On the Swedish peninsula alone, 45,000 people depended on fishing at that time. To this day, more than 400 years after complete overexploitation, only the spring-spawning herring (which is also overfished today) occurs in the Baltic Sea.
We can learn from this history and, on this occasion, shift our focus from the plate to the future.
Since 2015, the estimated spawning stock biomass of cod has been below a critical threshold. Since 2022, commercial cod fishing has therefore been prohibited, with the exception of approximately 500 tonnes of permitted bycatch. Recreational fishers are still allowed to retain one cod per day.
It remains to be seen whether these measures will be sufficient to prevent the socio-economic and ecological system from permanently losing its equilibrium.
Sources:
Lehmann, O., Schmidt, J., Voss, R., (2021): „De vorbisteringhe deß heringheß uthe deme Sunde“ - Indizien für eine vorindustrielle Überfischung des Ostseeherings. Hansischen Geschichtsblätter (Volume 139/2021)
European Commission: Fishing opportunities in the Baltic Sea for 2023.
