The Municipality of Silves is monitoring the situation together with the Portuguese Environment Agency (APA), after measurements taken at the site showed oxygen levels of around 10%, compared with normal levels of approximately 90%, as reported by Algarve Primeiro.

The municipality explained that the low flow of the Ribeira de Alcantarilha, combined with high temperatures and limited renewal of the water, has led to a sharp reduction in the amount of oxygen available.

At such low levels, conditions become unsuitable for fish to survive and can also lead to the death and decomposition of algae and other organic matter.

Municipal teams have already started removing the dead fish to reduce the environmental impact and prevent problems caused by their decomposition.

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Silves Council has also made staff and machinery available to temporarily open a passage between the stream and the sea. The measure would allow seawater to enter and help renew the water in the Ribeira de Alcantarilha.

However, the operation can only be carried out at high tide and requires approval from the APA, which is responsible for the watercourse.

Before authorising the intervention, the environmental agency was waiting for the results of microbiological tests carried out on the water.

This is not the first time fish deaths have been recorded in the Ribeira de Alcantarilha. A similar situation occurred in 2024, when the mouth of the stream was eventually opened to the sea following severe water shortages and low oxygen concentrations.

The municipality said it would continue monitoring the situation with the APA and removing dead fish while waiting for conditions that allow further intervention.