Table 1.

AGD scoring system [72]

AGD score	AGD severity	Description
0	Clear	No sign of infection and healthy red colour (non-symptomatic)
1	Very light	1 white spot, light scarring or undefined necrotic streaking
2	Light	2–3 white spots/small mucus patch
3	Moderate	Established thickened mucus patch/ white spot groupings up to 20% of gill area
4	Advanced	Established lesions covering up to 50% of gill area
5	Heavy	Extensive lesions covering most of the gill surface (over 50%)

Fish were classified depending on visual inspection of the gills. White spots and mucus patches on the gills are typical indicators of an AGD infection