Effects of transport densities on the physiological and biochemical characteristics of sturgeon (Acipenser baerii ♀ × A. schrenckii ♂)

Transport procedures usually cause fish stress, especially at high densities, which might cause considerable stress and compromise product quality for adult fish. However, many previous studies of density on sturgeon have hindered understanding of its roles in the physiological change during and after the transportation of sturgeon and no study explored high density as fish-to-water ratios up to 1:1. The objective of this study was to investigate the effects of transport density and duration on antioxidant indices, immune response, and post-transported recovery time of adult sturgeon (758.30 ± 42.8 g, one and a half years old) during long-distance and high-density transportation. Sturgeon were anesthetized with MS-222 under different fish-to-water ratios of 1:1 (D1), 1:2 (D2), 1:3 (D3) and 1:4 (D4), and simulated transport was carried out for 0 h, 1 h, 6 h, 24 h, 48 h and 72 h, and resuscitation was carried out for 6 h, 24 h and 48 h after transport. The relevant measurements were made on the water and serum samples. The findings demonstrated that after 72 h of transportation at various densities, the survival rate was 100%. Total ammonium nitrogen concentrations in the water increased in parallel with the stocking density after 48 h. After 72 h of transport, blood levels of malondialdehyde (MDA), glutathione peroxidase (GSH-PX), catalase (CAT), glutamate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and total protein (TP) were substantially higher in group D1 than in group D4 (P < 0.05), although serum levels of MDA, cortisol (COR), TP, and immunoglobulin M (IGM) in group D2 were not statistically different from those in group D3 (P > 0.05). To cope with the pressure imposed by high-density transport, the antioxidant, metabolic, and immunological indexes of sturgeon in the D1 and D2 were significantly greater than those of sturgeon in D4 group during transport. The D1 group had the most severe damage to antioxidant, metabolic, and immune abilities after resuscitation, and at 48 h after resuscitation, the levels of MDA, AST, and IGM were still significantly higher than those in the control group (P<0.05), whereas the levels of IGM in the D2 group were not significantly different (P > 0.05). Sturgeon under anesthesia should not be transported for longer than 72 h at a time with a fish-to-water ratio of 1:1 because doing so resulted in irreparable harm to all fish indicators. To better comprehend the circumstances necessary for efficient transportation, the study may contribute to evaluate the changes in physiological and biochemical characteristics of sturgeon.