Good Health and Welfare of Farmed Fish
Maintaining good health and welfare of fish is a fundamental aspect of fish management and vital to secure a sustainable future for the rapidly growing aquaculture sector. Welfare has a direct and profound effect on the health, survival, productivity of our farmed fish, as well as the quality of the final product.
Every management procedure we impose on our fish stocks from the egg to the final harvest will have an impact on the welfare of the fish by causing stress or even damage. The stress response in fish, as in other animals, is a protective mechanism which allows the fish to cope with changes imposed on it. Stress itself does not necessarily have a negative effect on fish production, it is usually only when there is continuous or repeated stress that it becomes damaging to the fish by increasing risks of clinical disease, poor growth and poor survival. This in turn is reflected in increased mortalities, lower productivity and feed conversion. By ensuring the best welfare at all stages of the production cycle, stress and damage are minimized and the chances of successful fish management and higher productivity are greater.
Farmers need to know where impacts on fish welfare occur. These may be the obvious management procedures such as transport, grading, crowding and other handling activities. However, a good stockman will also be aware of more subtle stresses to the fish such as noise, light, vibration, human activities and small changes in water quality. For example, it is important to have procedures and practices in place to mitigate the impact of such stresses, like a drop in dissolved oxygen levels at night.
Stress and related damage to the fish can also be minimised by deploying ‘best practice’ management procedures, including low impact passive grading, rather than mechanical grading and ensuring very gentle crowding techniques with optimum water quality.
Farmers must have empathy with their fish and understand where welfare may be impacted. Carrying out a welfare risk assessment throughout the production cycle to identify these risks and put procedures in place to help alleviate negative impacts on welfare is key. A good stockman will be able to recognise welfare indicators in terms of fish appearance and behaviour to give early warning of any problems developing and be able to act rapidly to protect their stocks. Good observation is absolutely vital for this and stocks must be closely monitored at all times during any management procedure. Due to the nature of aquaculture, this may need to be done remotely by camera observation to observe how fish are behaving e.g. during transportation.
Crowding pre-harvest is another example where close monitoring is vital to ensure that any signs of stress or poor welfare are picked up instantly and attended too. Overcrowded fish will quickly show signs of stress through increased activity at the surface of the water, their escape response, colour changes in their skin etc. Good farm practice and observation should pick up on such early warning signs and enact corrective action instantly.