230. In comparison with other farm animals, salmon and trout have been kept for farming for a short time and little modification has been achieved by genetic selection. Farmed carp may differ from natural stocks in minor body-shape changes but the major changes in body-shape have been achieved by selection in largely ornamental species, particularly goldfish Carassius auratus.
231. Genetic engineering by chromosome manipulation to produce all-female broods and triploid individuals is widely practised in trout farming. These have no obvious welfare implications. Future genetic engineering by gene transfer may have welfare implications.