Nofima reports

Rapport/Report 34/2016 - English Summary

Gjerde, Bjarne; Lein, Ingrid; Tanase, Cristina

Publication details

Publisher: Nofima AS

Issue: 34/2016

Number of pages: 16

International Standard Numbers:
Printed: 978-82-8296-410-4

Open Access: green


Reliable figures for the number of lice on salmon in cages is important to take measures against lice at the right time. Local lighting and weather conditions may affect the counting results at the cage. Nofima and Philips Lighting conducted a project (FHF 901044) aiming to identify reasons for possible deviations between reported and actual salmon lice numbers. Lice were counted on 20 fish/cage at three locations at Nordmøre every second week during February-April 2015 using three methods: standard counting at the cage, light box and magnifying lamp. There was no systematic differences between counting methods. The light box gave uncomfortable working positions and light conditions. It is important to report number of lice remaining in the anesthetic bath. Lack of coherence between light conditions and lice count contradicts the counters subjective opinion that light conditions are important and previous findings in Nofima. It should therefore be carried out a controlled experiment to study the effect of light intensity, additional lighting and type of additional lighting (fixed work lights, headlamps) on the lice count.