CLIMATE CHANGE IN GALICIAN FISHING (PART I)

Vigo is the biggest city of Galicia, which is situated in the northwest of Spain, and it is well known for its maritime and industrial activity. The highest amount of freshly-caught fish in Spain arrives to the port of Vigo, particularly, in 2014, 31.056 tons of fish, according to surveys made by “Puertos del Estado”. This figure places the Port of Vigo as one of the most important fishing docks throughout Europe.
Slightly changes in the environment deeply affect the marine ecosystem, which has (a) direct influence over fishing, causing both positive and negative consequences. In Galicia we have not been able to avoid climate change, therefore the number of captures and the distribution and the growth of the different species are currently suffering variations.
Despite the widespread belief, not only is the rise/increase of the sea temperature rise the responsible for (fishing) change, but also the pH level decrease. The rise/increase of the sea level rise or and the salinity drop represents are key factors that explain it.
To show different effects that each factor produce on the fishing, we can summarize some of them:
• Sea temperature rise: a rise of 0.2ºC per decade registered within our coast is the main reason why species from southern areas have been moving to northern ones where they were unlikely to live before. We are talking about Trachurus picturatus (horse mackerel) and Solea senegalensis (sole) among others. This, indeed, has had a positive effect on fishing because the captures have been increasing since the arrival of these species and they can perfectly coexist with local species, that is to say, they are not invaders (or "they are not invading?) (1).
• pH level decrease: a decrease of 0.0052 per decade, which is a significant value, is strongly very harmful for calcareous organisms (with shell)(2). To understand it, it is needed necessary to explain the process where CO2 is the main involved element. CO2 is present both in the air and in the water, in such a way that their concentrations are in equilibrium (or "...their concentrations are equal"). Therefore, the more CO2 within the air, the more in the water. In the sea, this CO2 chemically reacts with water, giving/making/creating carbonate (CO3-2), which is the principal component of the shells, and dropping its pH (acidification). This does not usually mean any kind of problem, in fact, this reaction is normal and the carbonate is usually in supersaturated conditions, without reacting.