Scottish Animal Welfare Commission: welfare of cleaner fish used in the Scottish salmon industry - report

8. Glossary

Crowding – the term crowding refers to the gathering of fish from a larger pen into a smaller space. This typically occurs before a treatment, transport or slaughter (Noble et al., 2018).

Thermal delousing systems – the use of a thermolicer involves crowding the fish before pumping them through a bath of hot water of up to 34°C (Overton et al., 2019). The warm water is If the water is above 28^oC, the fish show signs of pain (Nilsson et al., 2019).

Physical or mechanical delousing systems – these delousing treatments involve the fish being crowded and then pumped through a system where lice are removed using low pressure water sprays or turbulence (Overton et al., 2019).