We are increasingly attuned to the needs of animals, whether they are our beloved pets or our future food source. The more we identify with a species, the more empathy we feel. That’s why, in my opinion, we are extremely aware of issues related to the welfare of mammals, but not so much when it comes to fish. Fortunately, this is changing, as we now know that fish are sensitive animals, capable of learning, feeling pain, and actively trying to avoid stressful situations. Most fish are quite intelligent, in fact.

Let me be clear: the idea that breeders (not only of fish, but also of livestock, poultry, etc.) will do anything for profit, and that “anything” includes mistreating animals, couldn’t be further from the truth. Stressed animals don’t eat or grow well, which means that animal welfare is essential for achieving good production results. Therefore, European producers ensure that fish are raised respecting the maximum densities (number of fish per tank or cage) that allow for the expression of normal behavior.

However, there are critical production points where animal welfare may not be ideal. Examples include transport from the nurseries to the growing tanks and cages, and sorting, where fish are separated according to size to ensure that smaller fish are not preyed upon by larger ones. It is essential that the personnel involved in these tasks are well-trained and experienced and follow existing guidelines, such as those adopted by the Council of Europe. When fish are mishandled, they can be injured and more prone to disease, and nobody wants that, least of all fish farmers, as it certainly results in economic losses.

Slaughter, of course, is another critical step. How to ensure animal welfare during slaughter? In Mediterranean fish farming (mainly sea bream and European sea bass), fish are removed with nets and immediately placed in a mixture of water and ice, between 0 and 2°C. The thermal shock anesthetizes the fish, making the process virtually painless and relatively quick, with death occurring after 30 minutes. In traditional fishing, fish are not slaughtered in this way, being left to die from asphyxiation, which can take several hours. Before harvesting, fish are typically fasted for 24 hours, which in itself is not considered poor welfare, as periods of low or no food availability are common in nature and, as such, fish are prepared for it. However, since fish raised in a cage or tank are not harvested all at once, the fasting period can be longer and cause stress as well as weight loss. It is therefore important that harvesting procedures (fasting and netting) are as short as possible and that cages are harvested alternately to allow for recovery. It is important to note that stressful slaughter practices accelerate the onset of rigor mortis and quality deterioration, leading to a lower quality product with a reduced shelf life. Again, nobody wants that, least of all fish farmers.

The use of crushed ice (as opposed to asphyxiation) improves animal welfare, but it is by no means a perfect solution. Ideally, an anesthetic with no withdrawal period, such as isoeugenol, already approved in countries like Australia, New Zealand, and Chile for this purpose, would be used. In the EU, however, as there are no studies on the impact of this type of product on human health, no anesthetic is approved for use during fish harvesting.

Over the past few decades, research has been conducted in the EU on fish welfare during production and slaughter. Proper handling of fish in aquaculture is a challenge, as many factors affect individuals and species differently. For example, in the case of salmon, a cold-water species, slaughter in a mixture of water and ice is ineffective, and other stunning methods are used, such as electric shock or percussion (also used in terrestrial animals such as poultry, pigs, and cattle). However, these methods are difficult to use on smaller species and, currently, there are no commercially available options (percussive or electric) for use in Mediterranean fish farming. Research on this subject is ongoing and, as soon as suitable alternatives emerge, they will certainly be adopted by our fish farmers. Until then, we minimize the impact on animal welfare by optimizing procedures, carried out by qualified professionals who ensure that the negative impacts of current practices are as small as possible, and we encourage much-needed research to develop pre-slaughter and slaughter methods that avoid stressing the animals.

Elisabete Matos