We have detected high concentrations which, on several occasions, have exceeded a hundred specimens, with a maximum of 455, the highest ever recorded in Catalonia. This is an exceptional event on the Catalan coast, since groups of more than 100 individuals have never been detected before.
In recent years it has been observed that open ocean aquaculture facilities tend to attract different species of seabirds. These structures, as well as becoming an excellent meeting and resting point, also turn into a feeding site for different species, among which stands out the European storm petrel (Hydrobates pelagicus), the smallest seabird in Europe, which has a Mediterranean subspecies.
To analyze the relationship between these fish farms and the presence of seabirds, from 2015 to 2021, BioSciCat carried out a study on the interactions between different seabird species and bluefin tuna (Thunnus thynnus) fattening facilities, in the Ametlla de Mar, with the collaboration of the Balfegó S.L. group.
Study results
In 2015, concentrations never previously reported in Catalonia were discovered, which have been repeating every year, especially before breeding, and when it is ending. The storm petrel does not breed in Catalonia. The closest colonies are in the Columbretes and the Balearic Islands. Recent studies show that they can travel more than 400 km from their breeding colony to feeding sites.
It appears, therefore, that the activity carried out in fish farms provides predictable feeding opportunities for storm petrels, which allow them to save energy and time. This is especially relevant in critical periods, for example, when they leave their colonies and go into the high seas looking for food for their chicks.
In these cases, having a reliable source of food can increase the survival and breeding success of the species populations. It would be necessary to go deeper into the study of the effects that the use of bluefin tuna farm’s facilities may have as feeding areas.
The results of this study can be browsed in the paper we have published in volume 64 (2021) of the Bolletí de la Societat d’Història Natural de les Balears: https://ibdigital.uib.es/greenstone/sites/localsite/collect/bolletiHistoriaNatural/index/assoc/Bolleti_/2021v064/pdf.dir/Bolleti_2021v064.pdf (English version).
However, there are still many unanswered questions about the biology and conservation of this enigmatic pelagic species.