Research Article: Study on formulated diet for large yellow croaker (Larimichthys crocea) larvae at the early feeding stage

Most hatcheries in China rely on live prey for successful rearing of fish and shrimp larvae. Besides the high costs, live prey with pathogenic bacteria also increases the risk of contracting foodborne diseases. More than ۳.۵ billion large yellow croaker (Larimichthys crocea) larvae (total length over ۴-centimeters) were raised in ۲۰۱۶. However, no formulated diet is available for replacing live feed in early stages of this croaker so far. In the present study, a new microdiet (Yq) is investigated for rearing croaker larvae at early stages (۱۵ days after hatching). A commercial import diet (Cd) and live prey (Lp) were fed as controls. About ۲۰,۰۰۰ larvae per tank were hatched from Ningde Fufa Fishery Company in May ۴th, ۲۰۱۷. Quality parameters, such as growth performance, survival and three digestive enzyme activities were measured. The survival rate of Yq (۵۸.۵%), Cd (۵۱.۵%) and Lp (۶۹.۶%) exhibited no significant difference (p>۰.۰۵). Furthermore, the cost of Yq was only about ۲۳.۳% of the cost of Lp. Specific growth rate in Lp was about ۸ times higher (p<۰.۰۵) than that in two other microdiet treatments. Tryptic activity was slightly higher than other enzymes’ activities, revealing that trypsin plays an important role in the degradation process of large yellow croaker larvae. In the Lp group, tryptic activity was ۴ times higher than that of the other two groups. In addition, the activity of three diets on α-amylase and lipase activities were not significantly different (p>۰.۰۵). The high survival rate and low cost of Yq showed that it is suitable in rearing Larimichthys crocea larvae at the early stages.