Fish Behaviour and Welfare

Fish are farmed intensively in aquaculture which is an economic necessity to provide large quantities for the food industry yet many species’ normal behaviours may be impaired by the nature of intensive aquaculture. Recommendations have suggested that for optimum welfare, animals should be able to express their natural suite of behaviours. Confining large migratory species such as salmonids to relatively small tanks or cages means they are unable to perform the extensive migrations performed by their wild counterparts so are these fish frustrated? When considering why salmonids migrate, their motivation is to find food yet if they are well fed by the farmer does this dampen the desire to migrate? The conflict of behavioural needs and the major welfare issues in aquaculture highlighted by recent scientific studies are discussed by Ashley. Species specific requirements are an important issue since fishes are one of the most diverse vertebrate taxa on the globe. Salmonids require the ability to swim constantly whereas flatfishes require ample space to rest on the substrate. When space is limited for flatfish, such as the commercially important halibut, they perform stereotypical surface swimming which has not been observed outside of the fish farm. Kristiansen and Fernö investigate individual variation in response to floating or sinking food pellets and find that stress coping style results in some individuals showing poor growth when fed floating food but their well-being improves when given food that sinks. These small changes in aquaculture procedures can make a real difference to fish growth and hence improve welfare and economic return