Nofima reports

Rapport/Report 59/2016 - English summary

Roth, Bjørn

Publication details

Publisher: Nofima AS

Issue: 59/2016

Number of pages: 41

International Standard Numbers:
Printed: 978-82-8296-458-6

Open Access: none


Optilice is a commercial system for removal of the parasite sealice (Lepeophtheirus salmonis) and (Caligus elongatus) using temperate seawater (28-34 °C) for 20-30 s on Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). Test under commercial conditions treating 50-100 tons/h show that 98 % of all mobile pre and adult sealice, are removed. The attached stage as chalimus is not. The temperate water has minor effect on the welfare of the fish. Histology shows no necrosis of gills, the fish had a nice mucus layer intact and treated fish gained appetite within the next day. Water and blood analysis do not show evidence of hypoxia during treatment. The welfare challenge is mechanical injuries and the fact salmonids has the ability to injure itself during the process. Large scale experiments shows that treatment causes and increased mortality of approx. 0.1-0.2 % within 24 h. Over the following month, the mortality increases to 0.5 %. Main cause is physical trauma. Conclusion is that temperate seawater is efficient for removing mobile sealice on salmonids. The welfare of the fish is dependent on both operational conditions such as crowding, and dewatering and mechanical such as pumps, impellers and temperature regulation systems.