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.
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.