Forsøksdyr: Temperature-dependent development rate of Caligus elongatus

Godkjenningsdato 02.06.2020

Godkjenningsperiode 03.06.2020-31.12.2021

Salmon lice (Lepeophtheirus salmonis) have temperature-dependent rate of development, which has recently been described. However, this knowledge is lacking for Caligus elongatus, which is another ectoparasite that is rising in commercial significance in Norway. The aim of this study is to establish the development rate of C. elongatus at different temperatures (4, 8, 12 and 16°C), while also investigating temperature influence on size, infection success, accumulated mortality and egg production.

As Atlantic salmon will be infected with C. elongatus for the duration of the parasite's life, some adverse effects are expected; there will be mild stress on the hosts during infection however this is not expected to be high as the number of parasites per fish will be relatively low (approx. 5-10) for the fish's body size. Temperatures will also be below what has previously been observed to be 'stressful' for the fish with infection.

The expected benefit of this dataset is increased knowledge of the biology of C. elongatus and how temperature influences their epidemiology - this species is rising in significance particularly in the northern regions of Norway, and this study will provide scientific documentation to be used by biologists, farmers and authorities.

This study will use 480 Atlantic salmon of ~150g: 4 temperatures will be tested, and each temperature will have 4 replicate tanks of 30 fish per tank. Tanks will be sampled on a rotating basis so fish will not be disturbed too often. This number of animals is based on the frequency of samplings required, and power of analyses estimated from previous trials of the same design.

Replacement: is not possible here as a live host is required to propagate the parasite and for 'normal' growth.
Reduction: the minimum number of fish is proposed, to ensure robust experimental design and data collection.
Refinement: handling is minimised and fish will be lightly sedated during transfers to reduce stress. Tanks to be sampled will be rotated within temperature groups, so that the same tank is not disturbed too frequently. All technicians and researchers involved will have experience with this species.