Some of the key farmed fish welfare issues we are working on are as follows.
Stocking density (the weight of fish kept in a given volume of water) is often thought to have a big influence on their welfare. However research and practical experience has shown that, on its own, stocking density is not necessarily one of the most important things affecting whether fish have a good quality of life. Some fish seem to prefer a higher stocking density, while others prefer lower stocking densities. Having stocking densities that are too low can cause certain species of fish to become territorial and aggressive towards each other.
Water is the main life support system of the fish, and the ‘quality’ of the water (temperature, pH and oxygen levels, etc.) will have a big impact on fish welfare. Again, some fish survive better in certain conditions than others. We believe that much more work needs to be done on some aspects of water quality such as carbon dioxide levels, which may impact on fish welfare if levels are too high. Similarly, increasing the water temperature when the fish are small can make them grow more quickly, but if the fish grow too fast during this time it can result in spinal deformities.
Farmed fish are sometimes handled, for example, when they are being vaccinated or when they are being graded according to their size. These procedures can be stressful for the fish, for example if they are taken out of the water, and it is essential to keep handling to an absolute minimum.
There are a number of ways in which fish can be transported, the most common being by road, boat or helicopter. We believe that all transport can be potentially stressful for the fish, so extra attention is needed during the process, particularly when the fish are being loaded and unloaded. It is also essential to be able to maintain the correct water quality (see above) for the whole length of the journey, even if delays or emergencies make the journey much longer than expected.
A number of slaughter methods are used in aquaculture. We believe that the only method of slaughter which is acceptable in terms of animal welfare is percussive stunning followed by bleeding (at present we are still evaluating the use of electricity to stun / kill fish). Other methods such as the use of carbon dioxide, suffocation in air or on ice, or bleeding the fish without stunning are all unacceptable on animal welfare grounds.