Modelling shows potential spread of algae bloom near Haugesund.
A bloom of the harmful algae Pseudochattonella remains present across several salmon farming regions in southern Norway, with authorities warning of a high risk of behavioural changes and increased mortality in affected areas.
In a status update published Tuesday, the Institute of Marine Research said the bloom is still present in the southern parts of Production Area 1 (PO1), parts of Production Area 2 (PO2), and in the outer and southern sections of Production Area 3 (PO3).
Algae analyses show moderate to high concentrations in some locations, which researchers say may affect fish behaviour and lead to elevated mortality.
Incident reports have been received from sites north of Haugesund in PO3 and from the eastern part of Boknafjorden. Monitoring data in PO2 show large variation between sampling points, with higher densities in exposed southern coastal areas and moderate concentrations inside Boknafjorden.
Drift modelling carried out by the Institute of Marine Research suggests the outer parts of PO3, from Haugesund to Selbjørnsfjorden, may be at risk of further spread. The speed of dispersion will depend on wind direction, wind strength and local current conditions.
Based on the incident reports and modelling, the risk level for the Haugesund–Selbjørnsfjorden area is currently assessed as moderate. For the inner parts of PO3, where monitoring data remain limited, the risk is considered low.
Further south, the risk remains high in areas south of Arendal. Monitoring data show a reduction in Pseudochattonella concentrations at the Arendal station in recent days, suggesting the bloom may now have moved past the area.
Farmers operating in PO1 and the outer parts of PO2 and PO3 have been advised to remain alert for behavioural changes or increased mortality in fish and to report incidents to the Institute of Marine Research.
