Production of protein hydrolysates from skipjack tuna (Katsuwonus pelamis) viscera as feeding attractants for Asian seabass (Lates calcarifer)

Skipjack tuna viscera hydrolysate (TVH) was produced by enzymatic hydrolysis using alcalase. A study of the effect of time and enzyme concentration was performed and formed the basis for preparing TVH with the desired degree of hydrolysis (DH). An enzyme to substrate ratio of 5 g kg−1 (TVH A1) and 16.4 g kg−1 (TVH A2) at pH 8.0 with a temperature of 50 °C, and hydrolysis time of 60 min were found to be optimal conditions to obtain hydrolysis of 42.9% and 62.9%, respectively. Both TVH A1 and TVH A2 were analysed for chemical and amino acid composition and peptide size. The effectiveness of TVH at different DH as feeding attractants was estimated in a feeding trial at different inclusion levels. Ten experimental diets, including a fish meal‐based reference diet, were fed to Asian seabass for 28 days. Fish fed the diet supplemented with 30 g kg−1 of TVH A2, and the reference diet showed the highest feed intake (P