Influence of Stocking Density on Growth, Digestive Enzyme Activity, Immunity, and Cortisol Levels of Subadult Half‐smooth Tongue Sole Cynoglossus semilaevis in a Recirculating Aquaculture System

Abstract

According to the authors' experience of culturing Half-smooth Tongue Sole Cynoglossus semilaevis, high stocking densities lead to production failure, but few studies have addressed the problem. The purpose of this experiment was to evaluate the impact of stocking density on the growth and physiological parameters of subadult (700-1,200 g) Half-smooth Tongue Soles. The experimental design was completely randomized with three replications and one factorial scheme with three stocking densities: low density (LD; 200 fish/tank, 3.51 kg/m 2 ), medium density (MD; 300 fish/ tank, 5.30 kg/m 2 ), and high density (HD; 400 fish/tank, 7.06 kg/m 2 ). After 90 d, final mean body weight in the LD group was 1,003.4 g, which was 7.85% higher than that in the HD group. In addition, the activities of digestive enzymes (lipase and amylase) were depressed in the HD group relative to the other groups. Levels of immunology indicators (lysozyme, total superoxide dismutase, catalase, and glutathione peroxidase) were significantly lower in the HD group than in the LD and MD groups. The cortisol concentration was significantly higher in the HD group than in the LD and MD groups. These results show that growth, enzyme activity, and cortisol levels in Half-smooth Tongue Soles are negatively affected when the fish are cultured at high stocking density.

Effects of stocking density on the growth performance, mitophagy, endocytosis and metabolism of Cherax quadricarinatus in integrated rice–crayfish farming systems

“…An increasing stocking density induces oxidative stress leading to high catalase (CAT) activity and malonaldehyde (MDA) content in channel catfish ( Ictalurus punctatus ) ( Refaey et al, 2022 ). In addition, some studies demonstrated that high stocking density could decrease digestive enzyme activity ( Liu et al, 2018 ) and change body composition ( Aidos et al, 2018 ). Hence, an appropriate stocking density is vital in aquaculture, which may take into consideration both welfare of animal and economic benefits of farming.…”