Welfare of fish used in scientific trials on the agenda

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By Milthon Lujan

Norway.- We use many thousands of animals in experiments yearly. The most used species in Norway is not mice but a fish: the Atlantic salmon. Optimisation of the environment of animals used in testing is frequently on the agenda. But does this also apply to fish?


Nofima, in cooperation with the Institute of Marine Research and Norecopa, is working to figure this out. During the two-year research project ENRICH Fish, many attempts have been undertaken to map the conditions that affect Atlantic salmon placed in pens at various stages in their life-cycle.

In summary: can one use knowledge of fish welfare to improve conditions for fish used in experiments? Can today’s practices be improved?

Many questions

The conclusion after two years’ work is that fish that are placed in standard pens and used in testing for the development of feeds and vaccines are relatively well. They develop as expected, based on their species in the wild.


But can one get salmon to thrive better in pens? A standard experiment provides little variation in environment for the fish. To minimise variations between treatments other than those factors one wishes to study, it is important to have as little variation between pens as possible. If variation is high, one must increase the number of fish in the study to gather enough data to conclude. If variation is small, one requires fewer fish. Salmon in the early life stages—the freshwater phase, before migration to the sea—are temporarily adapted to variations in environment, such as in water currents and places in which to conceal themselves. How important is such variation for salmon, and are they affected by a lack of variation? And how, then, can we enrich their environment so that the research pens mimic the conditions to which the fish originally adapted?

”After the project, we have some answers, but also a number of new questions. The experiments so far indicate that the welfare of the fish is seen to, and that the various attempts to vary their environment do not provide significant results. Because the project was relatively limited in scope, there are many things we might study further. Amongst other things, the requirement to limit the number of experimental animals seems to reduce animals’ welfare in some instances, and thus goes against its intended purpose,” says Senior Researcher Chris Noble at Nofima, who led the project.

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Enriched environment

Growth, appetite and injuries on the fins and skin are used as welfare indicators for fish. Feed, water temperature and other factors that can affect life in the pen are also important for good growth conditions for fish in trials. During ENRICH Fish, testing was undertaken to enrich the environment of fish in trials, to see if this gives any insights into either the growth and habits of or ways to minimise external injuries to the fish. Amongst the tests carried out was a test giving the fish various opportunities to hide, both from the surface and from other fish in the pen. There was also a test ”furnishing” the pens with stones and artificial seaweed to offer the fish more variation in their surroundings.


”The conclusion was that the fish used the furnishings, but as expected, cleaning became complicated with stones and seaweed in the pens. We predicted this, and we had therefore decorated some pens with pictures of stones and seaweed wrapped in plastic wrap and glued to the walls and floor. The two-dimensional pictures appeared to give the same benefits as the three-dimensional elements,” says Chris Noble.

During the project, the research team also examined the influence of group size, as well as the number and density of fish in the pens. They further examined the meaning of pen size and how moving fish from one pen size to another affects the fish in experimental trials.

”Group size, with a lower limit, has meaning for how salmon perform in trials. It can thus be that social relations in the pens should be given more weight than group size. The results also show that fish that are moved to smaller pens than those they are used to have more problems fitting in within the new pen than when they are moved to a pen of the same or larger size, and that this should be taken into account when planning trials,” says researcher Jonatan Nilsson at the Institute of Marine Research.

Project leader Chris Noble has with him in the project group senior researchers Bjørn-Steinar Sæther, Atle Mortensen and Velmurugu Puvanendran from Nofima; researchers Ole Folkedal and Jonatan Nilsson from the Institute of Marine Research; and Professor Adrian Smith, secretary of Norecopa.


Norecopa is a national platform established by Norwegian government authorities, which has worked since 2007 to spread information on alternatives to animal testing. Norecopa strives for consensus between parties interested in animal testing: administration, research and teaching, industry and animal protection.

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The three Rs

Central to Norecopa’s work is the principle of the three Rs:

– Replacement (replacing testing animals with alternatives)
– Reduction (reducing the number of animals used in animal testing)
– Refinement (improving animal testing to reduce pain and suffering)


The researchers in the project also emphasize a fourth R: relevance.

”In our context, reduction is not as relevant as the other aspects. If the fish are well, it does not matter that there are many of them. We therefore consider it relevant to instead optimise the number of fish in trials rather than to reduce that number. It is, for example, not certain that the fish experience the conditions as better if the number of fish is reduced. Some species, including salmon, become more aggressive when there are fewer of them in the group,” says Bjørn-Steinar Sæther.

”Results from experiments with very low fish density will rarely reflect what one finds in the practice of fish farming with higher densities, and one risks that the results are misleading or irrelevant. If one is using animals in research, the quality and relevance of the research must be high,” says Jonatan Nilsson.

The project has shown that there should be more conscientious approaches to the surroundings of fish used in trials, and that those with benefits can be standardised, both within and between experiments.

”This will mean that results will become more comparable, and the need to undertake trials will be reduced. For a single experiment, this might mean that one must use more fish, but as this will provide more reliable results, the overall effect will be that the total number of experimental animals used will be reduced,” says Sæther.

This way of thinking is understood by Adrian Smith at Norecopa.

”We have documentation on optimal confinement conditions for mice, rats and other traditional testing animals, but there is very little information to be found on fish used as experimental animals. What the researchers reveal in this project is therefore an important contribution to our knowledge. We always have focus on using as few animals in testing as possible, but in some instances, there may be a need for a known number of individuals so that the animals can thrive,” says Smith.

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Dr. Penny Hawkins, section head of the British animal welfare organisation the Royal Society for the Prevention of Cruelty to Animals (RSPCA), took part in the reference group of ENRICH Fish. She embraces the project and hopes that the research currently underway will result in welfare standards for farmed fish, cleaner fish and other types of fish in captivity.

”Thousands of Atlantic salmon are used in laboratories and many millions are used in aquaculture. I believe that it is important to find out what can be done to improve the lives of these animals, and this project is an important step in the right direction,” says Penny Hawkins.

She believes that the fact that about 25,000 different species are ”squashed together” under the term ”fish” must also be changed.

”We lack documentation on standards, and we lack good practices for animal welfare when it comes to fish. This project is about Atlantic salmon. That can mean a lot for this species, and it pushes us in the direction of giving fish in scientific trials the same prioritisation as the so-called higher species,” she argues.

Contact person
Christopher Noble
Senior Scientist
Phone: +47 909 65 133

Bjørn-Steinar Sæther
Senior Scientist
Phone: +47 77 62 92 28

Source: Nofima

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