Transport and recovery of gilthead seabream (Sparus aurata L.) sedated with AQUI-S® and etomidate: Effects on intermediary metabolism and osmoregulation

Abstract

The improvement of aquaculture industry is directly linked to the improvement of fish welfare, as better growth rates are related to low-stress conditions for fish. In aquaculture facilities, routine processes such as live transportation activate the stress response compromising welfare of fish. As a solution, the use of anesthetics seems to reduce the negative effects of stress on fish physiology. There is a plethora of anesthetic compounds available, but their effects are however species specific. In this study, the effects of sedative concentrations of AQUI-S® and etomidate on physiological stress responses after a mimicked transport process, and further recovery, were evaluated. Gilthead seabream (Sparus aurata) was studied due to its great importance in European aquaculture. Prior to the transport assay, induction times to sedation, anesthesia and recovery were characterized for different concentrations of each anesthetic. Our results showed that AQUI-S® is more effective to induce deep anesthesia and require shorter recovery times than etomidate. Subsequently, seabream juveniles were placed in a mobile setup of water tanks, and transported for 6 h with a sedative concentration of either AQUI-S® (2 ppm of isoeugenol), etomidate (0.15 ppm), or without anesthetic. Afterwards, all groups were allowed to recover for 18 h in clean water tanks. Samples of plasma, liver and gills were collected before and after the transport process, as well as after the recovery period. The sedative concentrations of both anesthetics evoked differential responses in plasma and liver, and seemed to reduce secondary stress responses in gills compared to the control group. AQUI-S® induced additional plasmatic stress responses (increasing cortisol, glucose and osmolality) after transport. However, etomidate resulted more effective in the transport by reducing energy expenditure and promoting lipid synthesis in the liver. In conclusion, AQUI-S® resulted more suitable in short-term procedures where deep anesthesia is required; while etomidate was more effective to minimize stress responses in 6 h-transported seabream juveniles.