Aquaculturists and their organizations can be assessed in comparison to other people and organizations on moral, ethical and stewardship criteria. This chapter considers the criticisms directed towards aquaculture on ethical and stewardship grounds. Ethically irresponsible behaviour would lead to harm to humans in terms of health, economic or social well-being. Irresponsible stewardship would lead to harm to future generations of humans or to the sustainability of natural resources. Charges of irresponsible actions are assessed here only as they relate to the role of genetics in management of the production system. Genetics plays two roles in aquaculture: monitoring and modification. Use of genetic monitoring is generally associated with ethical operations exhibiting good stewardship. The genetic modifications of aquacultured animals are compared to those of maize in the context of responsibility. Genetic technologies for modifications include selective breeding, inbreeding. hybridization, chromosomal manipulation, gynogenesis, control of sex determination, cloning and production of transgenics. Aquaculturists have genetic responsibility for domestic populations and for wild stocks that are linked genetically to cultured animals. A large difference exists between genetic modification accomplished as research and that which is applied in commercial operations. In general, commercial aquaculture has not exhibited the same drive to commodification of genetic resources as the crop breeding industry. Selection of outbreeding populations is the principal technology employed. Traits selected for improvement are chosen for improvement of yield, not for mechanization or marketing advantages. Few production systems use more complex genetic technologies. Genetic modifications appear to improve the ethical responsibility of aquaculture operations. The analysis of responsibility for stewardship is less clear. The long-term impact of genetic management of aquaculture stocks may be loss of genetic variation. Genetics permits economic valuation of traits, but no method exists for incorporation of ethical or stewardship values. Aquaculturists should avoid genetic modification for irresponsible reasons and adopt precautionary management of genetic resources.