Effects of stocking density on growth performance and metabolism of juvenile Lenok (Brachymystax lenok)

Abstract

A 127 day growth trial was conducted to investigate the impact of stocking density on growth performance and metabolism of the lenok (Brachymystax lenok). Juvenile lenok were stocked in triplicate at 4 initial densities (0.74, 1.53, 3.15, and 6.11 kg m−3). Samples were taken at days 30, 60, 97 and 127 of the experiment. At day 30, a lower specific growth rate (SGR) with higher feeding rate (FR) and lower feed efficiency (FER) in the low stocking density group (D1; initial density, 0.74 kg m−3) was observed compared with the high stocking density group (D4, initial density, 6.11 kg m−3). In contrast, a reduced SGR in D4 at days 97 and 127 was observed compared with D1. However, significant metabolic differences of plasma and liver were only observed between D1 and D4 using nuclear magnetic resonance (NMR)-based metabolomics analyses at the end of the experiment, including activation of energy metabolism, alterations in amino acid metabolism, changes in choline metabolism and repression of lipid metabolism. Gas chromatography-mass spectrometer (GC–MS) was then used to identify specific fatty acid in plasma, and the results showed that there were significant reductions of n-3PUFA, n-6 PUFA, MUFA and SFA in D4 compared with D1 at day 127. In conclusion, high stocking density resulted in detrimental effects on growth performance and alterations in metabolism of the lenok, suggesting that the welfare of the lenok at this size could be adversely affected by high fish density.