Freshwater (pre-smoltification/juvenile fish)
RSPCA welfare standards for farmed Atlantic salmon 23 September 2015
* indicates an amendment
FW 1.6 The following water quality parameters must be complied with when water quality is managed.
Parameter Ova Alevins Fry Parr/Smolt
Oxygen (O2) mg/l 7.0 7.0 7.0 7.0
saturation % in exit
>90.0 >70.0 >70.0 >70.0
(N/A for Green
<0.025 <0.025 <0.025
<10.0 <6.0 <6.0 <10.0
Max temp °C 8.0 10.0 to 12.0 12.0 to 14.0 16.0
Min temp °C 1.0 1.0 1.0 1.0
pH in inlet water 5.5 to 8.0 5.5 to 8.0 5.5 to 8.0 5.5 to 8.0
<25.0 <25.0 <25.0 <25.0
mg/l <0.2 <0.2 <0.2 <0.2
Nitrate mg/l † N/A <50.0 <50.0 <50.0
† The RSPCA acknowledges that for fully functioning recirculation systems nitrate levels will be above 50mg/l.
Super-saturated water can compromise fish welfare. Levels of oxygen, carbon dioxide and
nitrogen should be regularly monitored in order to avoid this. As our knowledge of the water
quality needs of the fish improves, it may be necessary to change and/or add to the constituents
in FW 1.6. For example the inclusion of parameters associated with the mineral content of the
water may be appropriate as we get more information about their effect on the welfare of the fish.
In order to ensure due diligence with regard to the welfare of the fish, it is expected that all water
quality parameters with the potential to affect welfare are measured.