A "periodic" phenomenon, caused by the wave of intense and sudden rains in recent days. Following the fish kill recorded in Su Siccu five days ago, Cagliari's Local Health Authority (ASL 8) has provided reassurances. As explained by the directors of the Animal Health and Food Hygiene Veterinary Services, Drs. Bianca Falchi and Andrea Puddu, the heavy rainfall has washed away the sludge present in the canals, dislodging the anaerobic bacterial flora that had previously been immobilized on the lakebed.

This suddenly alters the canal waters, which from lagoonal, that is, with intermediate salinity, suddenly become fresh, even though the fish are able to adapt to the decrease in salinity, but slowly, in the lagoon . "So between the pollutants in the sludge and the salt shock , the fish don't survive. The mullets remain trapped between a surface layer with too low salinity, which causes osmotic stress, and a bottom layer with the right salinity but without oxygen, which causes asphyxiation."

"The lethal combination of these factors," Falchi and Puddu continue, "leads to the periodic die-off of grey mullet . Currently, in addition to the now few dead floating fish, there are already large grey mullet swimming up the canal, attracted by the nutrients carried by the water," the Directors point out. "This indicates that the ecosystem will rebalance very quickly. In any case, the recommendation is that the fish be disposed of, even if they are not environmentally toxic or infectious."

(Unioneonline/vf)

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