Welfare is a complex and multifaceted subject involving scientific, ethical, economic and religious dimensions. Animal welfare is often defined by how an animal copes with the conditions it lives in. An animal is in a good state of welfare if it is healthy, comfortable, well nourished, and able to express innate behaviour whilst not suffering from unpleasant states such as pain, fear, or distress. In aquaculture, consideration of animal welfare is now fundamental when making decisions on daily husbandry practices, and when choosing production systems.
There are a range of welfare indicators to consider when assessing welfare. These indicators should be species-specific, reliable, feasible and quantifiable. They should also provide information on the extent to which the animal’s welfare needs are being met. While there is no set framework for assessing welfare in fish, there are four distinct categories of welfare indicators which provide:
- Health status – Injury, disease status and immune response
- Physical status – Growth, respiratory rate
- Physiological status – Stress hormones
- Behavioural status – Food intake, swimming, aggression / hierarchy
Welfare Concerns in Aquaculture
Feeding: Failure to provide an appropriate diet in an attractive form may result in growth issues. Failure to provide the right amount of food at the right time may result in population hierarchy and malnutrition.
Health: Fish are routinely treated and vaccinated to prevent and manage diseases within populations. Health treatments typically involve crowding, handling and other adverse conditions that will cause stress and damage to individuals. For some disease treatments, brain damage is known to occur.
Grading: Fish are graded to produce like-sized groups for efficient husbandry and to prevent aggression/hierarchy. Grading involves crowding and handling that will cause stress and damage to individuals.
Transport: Fish are routinely transported from tank to tank or from site to site. Transport involves crowding, handling, changing water quality and other adverse environmental conditions that will cause stress and damage to individuals.
Stocking density: Stocking densities that are too high can have negative effects on welfare. High stocking density results in reduced growth, aggression, and an increase in fin erosion and external damage.
Slaughter: Fish are slaughtered following the production cycle prior to human consumption. Slaughter practices involve handling, crowding, and in some cases, pain. Muscle quality is severely affected when the slaughter operation is poorly managed. For any stunning/killing method to be considered humane, it is critical to demonstrate that it actually kills the animal, or at least causes unconsciousness that lasts until death. If the method does not cause an immediate loss of consciousness, then it is also necessary to demonstrate that it does not cause pain or distress before the animal becomes unconscious.