MORE THAN 10 tons of dead carp have been found in Barragem da Bravura, close to Lagos, a dam that supplies water to the boroughs of Lagos and Portimão. It is thought that the high temperatures could be the reason for the situation, but only laboratory tests being carried out this week will confirm the exact cause. Meanwhile, officials guarantee that the quality of the water has not been affected. “What seems unusual is that the
water temperature appears to be 25ºC throughout, whereas normally there is a stratification or, in other words, temperature layers. On average, water at the bottom of the storage dam would measure less than 10ºC, allowing the fish to protect themselves from high temperature conditions,” explained Valentina Calixto, vice president of the Comissão de Coordenação e Desenvolvimento da Região do Algarve, the commission for the co-ordination and development of the Algarve region. “This could be one of the causes for the death of the carp, which are more sensitive than other species to variations in temperature.”
Carnivorous bass, which are also abundant in the same dam, appear to have escaped harm. Although, having said this, in areas where a difference of four degrees between the surface temperature and the water beneath has been reported, no dead fish have been found.
Meanwhile, Valentina Calixto believes that the small algae that provide a food source for the carp “could have some toxicity”. For this reason, some specimens of the dead fish have also been sent to the Instituto Português de Investigação Marítima, the Portuguese institute for maritime investigation in Lisbon, which will proceed to “investigate if any other parasitic substance could be affecting the species”.
More than 100 people have been involved in the work to remove the dead fish from the Bravura dam, a task that also required the assistance of a mechanical digger.