Effects of stunning/slaughtering methods in rainbow trout (Oncorhynchus mykiss) from death until rigor mortis resolution

The effects of stunning/slaughtering methods (carbon monoxide asphyxia, CO; electroshock, E; asphyxia in the air, A) were studied in rainbow trout kept in freshwater at 12 °C. The fish were analysed for blood parameters, rigor mortis evolution, fillets shape changes over 48 h, and ATP depletion and Adenylate Energy Charge (AEC) in muscle immediately after death. Treatment Awas most stressful giving the lowest pH values during rigor evolution, the highest concentration of lactate (6.31 mM) in plasma and the lowest AEC values in the muscle. None of the three-stunning/slaughtering methods affected perimeter, length and height of the fillets, with exception for the area at 24 h and 48 h post mortem, which was significantly reduced by CO treatment (CO b A b E). Globally, CO and E treatments showed the highest ability in preserving muscle energy immediately after death, whereas treatment E resulted the most suitable method for slaughtering, based on blood and muscle indicators.