Animal Welfare & Euthanasia

Animal welfare and euthanasia

Significance in production, research and training

(special thanks to Dr. Trygve Poppe, who contributed to this section)

Good animal welfare is an important cornerstone for biologists, scientists or students working with animals and fish are no exception.  Knowledge of the normal anatomy, physiology and behaviour is crucial for understanding complex pathological changes and their pathophysiological development. Even more important, is our ethical responsibility as human beings towards animals that we keep for the purpose of increasing our knowledge and understanding, or to benefit from their production. There has been a tremendous change in attitudes among the public, the consumers and within the fish-farming community, towards animal welfare, or more precisely: fish welfare. This is now a component implemented within production strategies of most fish farming companies, and employees take mandatory courses in fish welfare. The shift in attitude is also reflected in international and national legislation and this increased awareness should also be reflected in the way fish scientists and laboratory personnel relate to fish kept as research animals, including those that end up on the necropsy table. In the UK for example, this is strictly regulated by the “Animals (Scientific Procedures) Act 1986”,  including procedure authorisation from ethics committees, licensing of establishments where fish can be maintained or experiments carried out, and responsibility assigned to  include  roles such as those for the Named Veterinary Surgeon. They provide advice on the health, welfare and treatment of animals within the licensed premises, a role that some of the authors of this manual have been undertaking for many years.

The specific aspect of sacrifice by euthanasia is also covered by legislation, which requires that the animal has to undergo a quick loss of consciousness, followed by cardiac or respiratory arrest and loss of brain function, aiming to the loss of pain perception. The technique must also minimize or reduce the distress of the animal before the loss of perception, usually achieved by previous anaesthesia. In the laboratory, fish can be killed humanely for scientific purposes by methods identified or referred to as “Schedule 1” (see links below).

 Options and regulations may differ if euthanasia is applied to fish meant for consumption, to laboratory animals, or to fish sampled for disease diagnosis, and it may also vary in different countries. Therefore, specific information should be sought to guarantee the application of the most adequate method, according to the situation and in order to comply with regulations. 

For experimental animals, this also includes adequate holding facilities. Among other considerations, attention should be paid to ensure best possible water flow and quality, appropriate light regimes, temperature and tank colour, ensuring they are in accordance with the biological requirements of the species. Procedures applied should minimise handling and induce only minimal stress, this will also help to minimise artefacts and ensure that results can be correctly interpreted. In the farming environment, increasing the water temperature when the fish are small can improve growth or make them grow quickly, but if fish grow too fast it can result in spinal deformities (Fig. 1) raising a welfare issue. 

EU legislation is in place to ensure that feed are not only safe for human, animal and environmental health; there is also regulation on the circulation and use of feed materials, the components and additives, feed hygiene and on genetically modified feed in animal nutrition (Fig. 2). Additionally, when farmed fish are unable to escape or evade water quality issues, such as algal and jellyfish blooms, this can also evoke ethical questions (Fig. 3).



Similarly, transport of juvenile fish can cause extensive stress and poses welfare problems. This is currently covered by the legislation and farmers have a legal responsibility to ensure animals are moved in a way that does not cause injury or unnecessary suffering (Fig. 4). In summary, although fish welfare has become of significance relatively recently, everybody currently dealing with fish have a duty to consider the effects of their action in the fish wellbeing. Awareness of animal welfare is our responsibility whether we keep fish as pets, for production, research or teaching purposes. The UK Royal Society for the prevention of Cruelty to Animals (RSPCA) has published “Welfare Standards for Farmed Atlantic Salmon”, and what follows below are the recommended links related to the subjects covered in this section: