Forsøksdyr: Cleaner fish welfare in the Atlantic salmon sea cages.

Godkjenningsdato 10.10.2018

Both the function (delousing capacity) and welfare of cleaner fish in salmon net pens are currently compromised, due to frequent disease outbreaks and high mortality rates. Careful attention to the species-specific biological demands is required. Unfortunately, knowledge on cleaner fish environmental tolerance ranges is still too limited. This project aims to establish basic knowledge of cleaner fish biology focusing on the two most important produced species: lumpfish and Ballan wrasse. Specifically, we aim to study:

- the survival rate for both species in relation to the environmental conditions
- to establish environmental preferences and tolerance limits
- to assess welfare in the sea cage
- to assess fish physiological state and immune capacity
- to build a cleaner-fish welfare index model (CWIM) scoring system on the existing one on salmon
SWIM system.
-to provide advise on cleaner fish welfare to the food authorities and the wider public

Cleaner fish will be transferred in salmon sea cages as biological control means on sea lice between the autumn 2018 - spring 2019, as a standard rearing practice. These cages will have detailed monitoring of vertical fish behavior (echo sounder), environment (continuous CTD-profiling) and an underwater online camera monitoring system.

Cage setup is as follow:

-n. 3 cages with 6000 salmon each + 600 cleaner fish max (5% per species) + echo-feeding system
(300 wrasses from September; 300 lumpfish from November)
-n. 3 cages with each 6000 salmon + 600 cleaner fish max (5% per species) + normal feeding system
(300 wrasses from September; 300 lumpfish from November)

We will utilise the opportunity given by the above experiment to also study cleaner fish behaviour, welfare and survival. To do this in detail, we apply to use 600 floy tags: 50 wrasse and 50 lumpfish in each of 6 cages.

Dead fish will be collected from each cage daily and frozen for further analyses (i.e. back deformity); on week 0, 4, 8 and 12 from the transfer in the cage for each specie, 10 fish per time point will be killed by overdose and sampled for a) CWIM score, b) gut contents (lice count) c)molecular analyses (480 fish in total).
Twice every week, an operator will observe cleaner fish with an underwater camera recording:
- behavior (i.e. resting; swimming; interactions with salmon; eating lice)
- distribution of cleaner fish at each depth.
- differences between eco v.s. normal feeding
The wrasse surviving into the winter will be followed for welfare and mortality assessment over the rest of the experiment.
REFINEMENT: Animals will experience normal husbandry practice and for those tagged we expect minimal distress during anaesthesia and tag insertion. Sampled fish will also be killed by a lethal dose of anaesthetic. REPLACEMENT: Farmed lumpfish and wrasse are chosen avoiding wild and endangered stocks. REDUCTION: The number/biomass of fish is chosen following the standard salmon farming procedure. The number of tagged individuals is chosen to minimise animal numbers but provide robust statistical results.