Mediterranean warming transforms fishing catches and income on the Catalan coast

• This is the main conclusion of a study led by ICM-CSIC and AZTI, which analyzes changes in catch and revenue composition over the past 20 years.

Barcelona, 21 March 2025. A new study led by the Institut de Ciències del Mar (ICM-CSIC) in collaboration with the Marine and Food Research Center AZTI has revealed significant changes in the fishing catch and revenue composition on the Catalan coast over the past 20 years. According to the study, these changes are linked to rising water temperatures in the Mediterranean, which range between 0.3 and 0.8°C per decade, reaching peaks of up to 2.5°C above the historical average in some years.

The research, published in the prestigious journal Global Change Biology, shows an increase in the relative contribution of warm-water species (tropicalization) and a decrease in cold-water species (deborealization), both in the catch and the revenues generated by fishing. These changes are affecting fleets and key commercial species in the region differently.

“Combining ecological and economic data allows us to gain a more comprehensive view of how Mediterranean Sea warming is impacting the fishing sector, with important implications for the sector’s management and adaptation” explains Lucía Espasandín (ICM-CSIC), the study’s lead author.

Differences between fleets and species

The study highlights that fleets operating in pelagic habitats, such as surface longliners, have been the most affected by the decline in cold-water species. This could mean greater vulnerability and economic losses as they depend on a limited number of target species. On the other hand, the bottom trawl fleet, which operates on the seabed, has experienced an increase in warm-water species in both catches and revenues. This could translate into a greater capacity for adaptation and new opportunities for the sector.

Among high-value commercial species, hake (Merluccius merluccius), blue whiting (Micromesistius poutassou), and Norway lobster (Nephrops norvegicus) have shown a decline in both catch and revenue, indicating that they face a dual threat: climate change and fishing pressure.

Special cases: sardine and octopus

According to the study, two species, sardine (Sardina pilchardus) and octopus (Octopus vulgaris), showed a particular trend: despite a decline in their catch, their revenue has increased. This highlights that the relationship between catches and revenues is not linear, as prices can fluctuate based on demand and market conditions.

Finally, the study emphasizes the importance of considering the spatial dimension in fisheries research. By analyzing data by ports along the Catalan coast, researchers identified significant differences in changing patterns that would have gone unnoticed in a more generalized analysis.

“This work not only helps us better understand the effects of climate change on fishing but also allows us to identify the adaptive capacity or fragility of specific fleets and establish priorities for fisheries management in the Mediterranean,” concludes Espasandín.

Confirmation of a trend observed in previous studies

These findings further substantiate the results of earlier research, which had already highlighted shifts in marine biodiversity as a consequence of global warming. A study led by AZTI and published in Nature Communications in 2024 examined the evolution of marine communities in European seas over recent decades, confirming a widespread trend of tropicalisation and deborealisation.

The study, which analysed historical data from 1,817 species in the northeastern Atlantic, the Mediterranean, and the Baltic, found that the increase in warm-water species is most pronounced in the Atlantic, while the loss of cold-water species is especially evident in the Mediterranean and the Baltic, regions where warming is occurring at a faster rate. Moreover, the research emphasised that these changes affect not only key commercial species, such as the Mediterranean sardine and the Baltic cod, but also entire ecosystems, disrupting food availability and trophic networks.

“Ocean warming is not only reshaping marine communities, but it also has direct consequences for fisheries and local economies. Adapting fisheries management to these changes will be essential to ensuring the sector’s sustainability in the years to come,” explains Guillem Chust, AZTI researcher and lead author of the study.

• Reference article: Espasandín, L., Ramírez, F., Ortega, M., Villarino, E., Chust, G., Sbragaglia, V., and  Coll, M. (2025). “Ocean warming effects on catch and revenue composition in the Northwestern Mediterranean Sea.” Global Change Biology, e70112. https://onlinelibrary.wiley.com/doi/10.1111/gcb.70112