The processing of fish leads to a significant removal of fish parts, such as heads, bones, guts, etc... This manual will provide technical guidance on fish silage, a process that transforms fish waste into a liquid mix of hydrolysed proteins, lipids, minerals and other nutrients, easily digestible by both terrestrial and aquatic animals. Fish silage could make a difference in terms of: environmental impact, through reduced levels of waste; animal health; and economic gains, as waste is converted into a valuable product that can replace expensive feed ingredients or fertilizers.