 Fish are consumed fresh , or may be preserved by traditional methods , which include combinations of drying , smoking , and salting , or fermentation . Modern methods of preservation include freezing , freeze drying , and heat processing ( as in canning ) . Frozen fish products include breaded or battered fillets , fish fingers and <unk> . Fish meal is used as a food supplement for farmed fish and for livestock . Fish oils are made either from fish liver , especially rich in vitamins A and D , or from the bodies of oily fish such as sardine and herring , and used as food supplements and to treat vitamin deficiencies . 
