The farmed fish industry
There are many species of fish used in aquaculture, and these are farmed in both freshwater and seawater. They are produced in a wide variety of systems, which range from closed systems, where the water is artificially re-circulated, to open systems where the fish are contained in more natural bodies of water, such as a pond or sea enclosure.
By 2030, with a predicted world population growth of another two billion people, aquaculture will have to produce nearly double its present levels in order to maintain the current rates of fish consumption per person. It is therefore very important that steps are taken to ensure that as many farmed fish as possible are reared under higher standards of animal welfare.
Farming of Atlantic salmon
Atlantic salmon is one of the most commonly farmed fish species in the UK, with farms mainly located in the Scottish highlands.
At the start of their lives, the fertilised salmon eggs are usually grown in trays. The eggs hatch into ‘alevins’ or ‘yolk sac fry’ and they spend time on the bottom of their trays until the yolk sac has been absorbed. They then start to rise up into the water column as ‘first feeding fry’. This is the start of the freshwater growing period, and they are transferred to larger tanks/freshwater lochs as the young fish develop. They spend a significant period of time in freshwater before they are ready to go to sea.
Eventually, certain physiological and external signals, trigger a transformation in the appearance and behaviour of the young salmon. These changes result in the young fish being ready to go to sea - a process called ‘smoltification’. There are a number of ways in which fish can be transported to sea, the most common being by road, boat or helicopter.
Once the fish are transferred to sea, this will be their home for the next one to two years. When they have reached the required weight, they are pumped or netted out of their enclosure and slaughtered. There are a number of ways that the fish can be slaughtered, some of which can cause welfare problems.