Hydrolyzed feather meal (HFM) is a by-product of the poultry industry. An increase in HFM incorporation in Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) diets has been described in North America (Poppi et al. 2011). HFM is an economical protein source with a relatively high digestible protein content for fish (Bureau et al. 1999). Studies found that replacing fish meal with limited amounts of feather meals in practical trout or salmon diets did not negatively impact fish growth and feed utilization (Bureau et al. 2000), while specific types of fish such as Nile tilapia and common carp (Cyprinus carpio L.) can thrive with up to 50 % replacement of FM by HFM (Abdel-Warith et al. 2001; Mendoza et al. 2001).

If you want to replace total fish meal with feather meal, you must concern amino acid profile of diet. Such ingredients have high amounts of Proline and Glutamine which are none essential. After that, amounts of EAA like Methionine, Histidine and Lysine are not enough to meet the requirements of fish such as  rainbow trout, tilapia or cat fish. So, we must concern amino acid requirement of each species in replacing dietary fish meal with other potential ingredients.

Thanks you're absolutely right