Fish farming is one of the fastest growing sectors of agriculture, attracting considerable attention to the question of whether existing farming regulations and animal welfare laws are adequate to deal with the expanding role of fish in feeding humans. The role of fish as model organisms in scientific research is also expanding -- a majority of research biology departments now keep zebrafish for the purposes of genome biology, and they are used widely used for basic neuroscience research. However, due to their diversity and distance from mammalian biology, fish pose difficult questions for the application of legal and ethical principles of animal welfare. This paper reviews the developing legal and scientific context in which such questions must be answered.