Dozens of dead fish appeared at the mouth of the Alcantarilha stream in Armação de Pêra on August 22.
This is a natural occurrence in periods of high temperatures and is usually related to lack of oxygen in the water.
Several species of fish were affected including flounder, bream, eels and yellow-eye mullet.
Armação de Pêra parish council president Fernando Santiago told Portuguese daily newspaper Correio da Manhã that “every year this incident happens around this time”.
He added: “The only possible solution to prevent the death of the fish in the future is to build a dock in the area. That would guarantee a permanent connection of the stream to the sea.”
A spokesman from the ARH told the Algarve Resident: “A technician visited the site and took samples of water, which are now being analysed. We received a request from Armação de Pêra parish council for the permission to open a link to the sea in the area.
“Only after we complete the analysis of the water and have the results, will we be able to give an opinion on this matter and decide what the best solution to the problem is.”