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Topic: Fish welfare

laks i merd Erlend Astad Lorentzen HI

Oppdrettslaksen er Norges viktigste oppdrettsfisk.

Photo: Erlend Astad Lorentzen / Havforskningsinstituttet

Farmed fish are Norway’s most important farm animals. Each year, over 350 million salmon and rainbow trout are put out in fish cages in the sea.

Disease, parasites and injuries that occur during handling and transport are some of the reasons why approximately 60 million of them (15–20%) die before they are big enough to be slaughtered. Some of those that survive also experience various welfare problems. Although only a relatively small percentage is affected, we’re still talking about millions of fish. Examples of production-related problems include vertebral deformities, late effects of viral infections and occasional lesions caused by bacterial infections.

In 2018, around 12 million wrasse and over 30 million farmed lumpfish were used in fish cages. These cleaner fish eat sea lice off the skin of the salmon. They perform a useful job, but very many of them get sick and die.

Overall, this means there are significant animal welfare issues in the aquaculture industry. As well as the problems experienced by the fish, these issues also result in big financial losses and harm the reputation of the industry. The industry, research groups and the authorities have therefore set a goal of reducing mortality rates at fish farms and improving fish welfare.

Why should we care about fish welfare?

The suffering of animals is the main reason to care about animal welfare. In addition, we know that animals reared in conditions in which they can thrive provide the best financial returns.

The Norwegian Animal Welfare Act (2009) protects all vertebrates, including fish, decapods, honey bees and cephalopods. The Act states that these animals have an intrinsic value over and above their utility value. Section 23 stipulates that “The animal keeper shall ensure that animals are kept in an environment which is consistent with good welfare, and that meets the animals’ needs which are specific for both the species and the individual.”

The book “Welfare indicators for farmed Atlantic salmon” defines animal welfare as quality of life as experienced by the animal itself (Noble et al., 2018). The key is for an animal to have a conscious qualitative experience of itself and its surroundings, as that will allow it to find the resources it needs, avoid dangers and weigh up different needs against one another.

Fish have a wide range of senses and a relatively large brain. They have a high learning capability and good memory, and display advanced individual and social behaviour. As such there is strong evidence that fish have a qualitative and conscious experience of being, and that their welfare is worth caring about.

How can we measure fish welfare?

Since we cannot measure what fish experience, we have to rely on indirect methods to measure their welfare.

Welfare needs are needs that have a negative impact on welfare if they are not met or are less fully met, and a positive one if they are met or are more fully met. They include, for example, vital needs like oxygen and safety, whose absence cause fear and discomfort, which in turn stimulate fish to avoid dangerous environments. We therefore assume that the degree to which welfare needs are met is closely associated with animal welfare, and that observations of the characteristics of the animal and its environment that tell us how well its welfare needs are being met are also good welfare indicators.

Examples of good welfare indicators:

  • fish growth
  • health and physiological function
  • fish behaviour
  • measurements of important environmental parameters like oxygen, temperature, carbon dioxide and other metabolites, to confirm that the environment meets the species’ environmental needs

How can we improve fish welfare?

To safeguard the welfare of farmed fish, they need to be kept in an environment where they can both thrive and cope. In addition, training and gradual adaptation can help the fish to cope with the conditions at the fish farm.

It is therefore important to have access to locations with good environmental conditions and little infection pressure from pathogens, as well as to adapt the timing of release to the environmental needs of the fish at the relevant stage of their lives. Various actions can also be taken to make the fish more robust, such as ensuring that all fish released have already smoltified and hence have developed tolerance to salt water
Viktig med gode miljøforhold for oppdrettslaksen. (Foto: Espen Bierud / Havforskningsinstituttet)

All farmed salmon are vaccinated against the most dangerous bacterial diseases. Without these vaccines, we would have enormous fish welfare problems, and the aquaculture industry wouldn’t exist in its current form. We still have significant problems with viral diseases, and as we lack good vaccines against most of them, new vaccines will play an important role in improving fish welfare.

Many fish are injured or killed during handling and when being treated against sea lice and parasites. This is because the equipment and methods used are too rough on the fish. This particularly affects fish that have been weakened by disease or poor environmental conditions. Developing gentler methods and using preventive farming methods that reduce the need for handling are important measures that could have an immediate impact on animal welfare. Epidemiological tools like fallowing large areas in order to reduce infection pressure and coordinating the release and slaughter of fish, or reducing infection between farms in other ways, will also have a positive impact. New methods such as land-based fish farming, semi-closed systems, snorkel cages and locating more farms further out to sea will also reduce infection pressure and the need for treatment, but they could also have some negative impacts on welfare, due to higher density and lower water quality at land-based farms, for example, or strong currents and waves out at sea.

Working towards better welfare

In the slightly longer term, selectively breeding fish with high tolerance levels for the environment at fish farms and pathogens may enable us to develop fish that are more comfortable with the conditions at fish farms and whose welfare is consequently better. For example, selecting broodstock with resistance to the viral disease IPN has led to a sharp reduction in the prevalence of this disease in recent years.

Fish farming is an art that requires extensive knowledge and skill. Mortality rates and the degree of welfare problems vary greatly between locations and producers, and many producers achieve excellent results. There is therefore a lot to be gained by learning from each other and extending best practice to all companies. The industry is currently working hard to do this.