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HAVBRUK2-Stort program for havbruksforskning

Using optimised environmental enrichment to improve the rearing conditions and welfare of Atlantic salmon in relation to the 3Rs

Alternative title: Gir økt diversitet i omgivelsene bedre levevilkår og velferd for Atlantisk laks i fiskeforsøk sett i forhold til prinsippene om de 3Rene

Awarded: NOK 4.0 mill.

The 3Rs approach to science was developed in the late 1950's and suggests scientific experiments should i) Refine their designs and approaches to improve animal welfare, ii) Reduce the number of animals used and iii) where possible, Replace live animals with viable alternatives. With regard to Norwegian R&D, fish are the most commonly used animals in Norwegian scientific procedures. For example, in 2013, 4.8 million fish were used in Norwegian research. The goal of the 'ENRICH Fish' project is therefore to develop and test operational and species-specific social and environmental enrichment techniques to improve the lives of all Atlantic salmon used in applied and fundamental research. IMR has completed all of its experiments on group size and tank acclimation. The goal of the group size experiments was to find the smallest possible group sizes in which behavioural relevance and welfare were maintained. Pre-smolts and smolts were kept at different group sizes ranging from 10-200 individuals and we found that group size has a large influence on the level of, and between-tank variation of aggression in salmon, especially in pre-smolts. Scale loss, presumably resulting from aggressive interactions, was higher and more variable between tanks in the smaller groups. Baseline levels of cortisol on the last day of the experiment increased with group size in pre-smolts. Generally, the different welfare measures for salmon held at stocking densities around 10 kg m-3 did not differ much from that of the highest density, and therefore 10 kg m-3 is recommended as a balance between limiting number of fish (Reduction) and requirements of the social environment (Refinement). In the experiment on the effect of change in rearing unit size on the acclimation rate, pre-smolt previously acclimated to 1 m tanks were transferred to new tanks that were either smaller (0.5 m), similar (1 m) or larger (1.5 m), and kept there for 9 weeks. Fish in the smaller tanks had reduced appetite for a longer amount of time than fish in the larger tanks and thus had lower growth. Scale loss was considerably higher in the smallest tanks, and least in the largest tanks. Baseline cortisol levels were more than twice as high as in the 1 m and 1.5 m tanks after 2 weeks but declined afterwards. The results clearly show that salmon pre-smolts acclimate slower and perform worse during acclimation when transferred to smaller tanks than to similar or larger tanks. Nofima has also completed all of its experiments on environmental enrichment. The first experiment investigated the effects of differing benthic, floating or over-water enrichment materials upon fish welfare and performance 5. Floating enrichment was the most successful enrichment material we tested and it improved tank acclimation times, reduced inter-tank variability in growth and feed intake and improved fish welfare. The second experiment was to evaluate the efficacy of i) 2-D simulated enrichment materials (photographic films applied to tank bottoms and sides that mimic complex habitats) against b) 3-D enrichment materials (actual benthic and floating substrates). The group with 3-D floating substrates (algae) grew significantly worse than other groups. Physical enrichment also affected tank self-cleaning. The lowest inter-tank variability occurred in the control, 3D and 2D ?benthic groups, but size variability decreased in all groups during the trial. There were tendencies towards reduced aggression in tanks with substrate, especially during the initial days. Results suggest that 2D benthic cobbles bring improved performance and welfare benefits to juvenile salmon rearing in the lab. Nofima?s final experiment tested dynamic enrichment, in the form of changes in the environment that the fish could perceive as variation. In one treatment group the water current was shifted 180 degrees once a day and the other treatment involved reduction in the water volume (height) of approximately 30 cm for 15 minutes every hour. The treatment groups tended to grow slower than the controls, but no significant differences occurred. Fin condition showed slight improvement in the treatment groups, but no significant differences were discovered. Dynamic enrichment did not show any positive effects on the growth performance of salmon, but there may be benefits for development of fin condition. Dissemination has been an important part of ENRICH Fish. We have held three Stakeholder workshops to communicate the outputs of the project in Oslo, Bergen and Tromsø. Norecopa has also created an ENRICH Fish multi-stakeholder platform to ensure project goals and objectives are delivered to all relevant stakeholders (researchers, regulatory bodies, governmental and non-governmental policy makers, the aquaculture industry, NGO's and the general public). The platform will stay active (via Norecopa) after the project has finished.

The overall vision of ENRICH Fish is to pursue and deliver the goals of the 3Rs (Refinement, Reduction and Replacement) with regard to the use of live fish in all Norwegian scientific procedures. The 3Rs framework suggests scientific experiments should i) refine their designs and approaches to improve animal welfare, ii) reduce the number of animals used and iii) where possible, replace live animals with viable alternatives. In 2011, fish accounted for 97% of all live animals used in Norwegian research and this equated to 1,578,589 fish out of a total of 1,622,714 animals used. 80% of these fish were from a single species, Atlantic salmon. Salmon also dominates Norwegian aquaculture production, with over 1.2 million tonnes produced in 2013 and the project will therefore focus on Atlantic salmon. The ENRICH Fish project aims to address and implement the 3Rs in all fundamental and applied fish procedures by using Environmental Enrichment (EE) to enhance i) the physical and ii) the social rearing environment of fish and bring daily husbandry and rearing practices closer to the species-specific physiological and behavioural needs of fish. This can be beneficial for overall data quality as poor welfare can increase variability and have an adverse effect upon the validity and quality of the data produced. EE is widely used in a diverse range of animal taxa and is increasingly used in fish rearing. It can improve welfare, survival, recovery from stressors and reduce aggression and anxiety in reared animals. ENRICH Fish will create a multi-stakeholder platform to ensure project goals and objectives are realised and efficiently distributed to relevant stakeholders. Its outputs can be used to develop a program for promoting and implementing the goals of the 3Rs in fundamental and applied fish research, one of the most widely used fish species in Norwegian R&D and aquaculture production.

Funding scheme:

HAVBRUK2-Stort program for havbruksforskning