Fish require diets containing 30 to 55% of crude protein and an amino acid supply precisely adapted to meeting the needs for optimal growth. Fish meal is an ideal protein source for aquafeed because it has a high protein level (65% to 72%) with an ideal proportion of all ten indispensable amino acids that meet the requirements of all fish species. However, finding alternatives to fish meal has become an absolute necessity in order to reduce the reliance of aquaculture on marine ingredients. Animal by-product meals (meat meal, bone meal, blood meal, poultry by-product meal, hydrolysed feather meal) are used as alternative protein sources in aquafeed in extra-European countries. Since the use of animal protein in aquafeed is forbidden in Europe (except non ruminant blood meal), more attention has been given to the use of plant protein sources which are available in large amounts on the market. The limitations as regards their incorporation in diets for fish are related to the level of protein, the amino acid profiles and the presence of anti-nutritional factors (ANF). Protein extracts from oilseeds and cereals are higher in protein than meals and pulses and lower in ANF but currently more expensive, thus limiting their use in aquafeed. Numerous studies undertaken with different fish species have led to improved knowledge on the potential of various plant ingredients. Blends of plant protein sources duly supplemented with the required indispensable amino acids can replace 75 to 95% of fish meal in almost all species, thus reducing the pressure of aquaculture on marine resources. Further research should focus on factors that can facilitate total replacement, on the origin of the adverse effects of ANF and on the dietary supply of micronutrients (minerals and vitamins) in order to improve the ormulation of totally plant-protein-based diets for fish.