Alternative protein sources in aquafeed: Current scenario and future perspectives Fishmeal is the main protein source for most commercially farmed aquatic species due to its high nutritional value and lack of anti-nutritional factors. However, its availability and high cost have prompted the search for alternative protein sources. This review examines the use of fishmeal and alternative protein sources on the health, welfare, and growth performance of major aquatic species. The inclusion levels of alternative protein sources range from 10 to 80% for plant-based and 2 to 100% for animal-based sources, with positive effects on health, growth, and fillet quality. However, high inclusion levels can negatively affect fish growth and metabolism. Mixing different protein sources can enhance nutritional properties. Plant-based protein sources, such as soybean meal, corn gluten meal, rapeseed meal, and lupin meal, are widely used as alternatives to fishmeal. Soybean meal is a high-quality protein source with a balanced amino acid profile. Fermentation can reduce anti-nutritional factors and improve nutritional value. Corn gluten meal is high in protein but low in essential amino acids. Rapeseed meal has high protein content but contains anti-nutritional factors. Lupin meal is a good protein source but can cause liver damage at high levels. Faba bean meal is rich in protein and starch but contains anti-nutritional factors. Pea meal is a good alternative but has lower nutritional value than soybean meal. Animal-based protein sources, such as poultry by-products, feather meal, and meat and bone meal, are also used as alternatives to fishmeal. These sources have a better amino acid profile and are more cost-effective. However, high levels of inclusion can negatively affect fish growth and metabolism. Insect meal is a promising alternative due to its high protein content and sustainability. Insect meal is rich in proteins, essential amino acids, vitamins, and minerals, and is considered a sustainable and economically viable alternative. The future of aquafeed formulation is expected to be based on the blend of different protein sources. Research is ongoing to find the most sustainable and effective alternative protein sources for aquaculture. The review highlights the need for further research to fill knowledge gaps and improve the sustainability of aquaculture. The use of alternative protein sources can help reduce the environmental impact of aquaculture and meet the growing demand for sustainable animal proteins.Alternative protein sources in aquafeed: Current scenario and future perspectives Fishmeal is the main protein source for most commercially farmed aquatic species due to its high nutritional value and lack of anti-nutritional factors. However, its availability and high cost have prompted the search for alternative protein sources. This review examines the use of fishmeal and alternative protein sources on the health, welfare, and growth performance of major aquatic species. The inclusion levels of alternative protein sources range from 10 to 80% for plant-based and 2 to 100% for animal-based sources, with positive effects on health, growth, and fillet quality. However, high inclusion levels can negatively affect fish growth and metabolism. Mixing different protein sources can enhance nutritional properties. Plant-based protein sources, such as soybean meal, corn gluten meal, rapeseed meal, and lupin meal, are widely used as alternatives to fishmeal. Soybean meal is a high-quality protein source with a balanced amino acid profile. Fermentation can reduce anti-nutritional factors and improve nutritional value. Corn gluten meal is high in protein but low in essential amino acids. Rapeseed meal has high protein content but contains anti-nutritional factors. Lupin meal is a good protein source but can cause liver damage at high levels. Faba bean meal is rich in protein and starch but contains anti-nutritional factors. Pea meal is a good alternative but has lower nutritional value than soybean meal. Animal-based protein sources, such as poultry by-products, feather meal, and meat and bone meal, are also used as alternatives to fishmeal. These sources have a better amino acid profile and are more cost-effective. However, high levels of inclusion can negatively affect fish growth and metabolism. Insect meal is a promising alternative due to its high protein content and sustainability. Insect meal is rich in proteins, essential amino acids, vitamins, and minerals, and is considered a sustainable and economically viable alternative. The future of aquafeed formulation is expected to be based on the blend of different protein sources. Research is ongoing to find the most sustainable and effective alternative protein sources for aquaculture. The review highlights the need for further research to fill knowledge gaps and improve the sustainability of aquaculture. The use of alternative protein sources can help reduce the environmental impact of aquaculture and meet the growing demand for sustainable animal proteins.