Crowding, pumping and stunning of Atlantic salmon, the subsequent effect on pH and rigor mortis

Abstract

An optimum setting for electrical stunning of Atlantic salmon under commercial conditions was tested and compared against percussive stunning before and after pumping and at increasing durations of crowding (0.5 and 3 h). For electrical stunning the fish were exposed to 60 V, 100 Hz AC + DC for 6 s after pumping. The results show that there were no significant differences in muscle pH or rigor index between fish exposed to electricity or a percussive force. Pumping and crowding did have a significant effect. Pumping alone halved the time until maximum rigor from 24 to 12 h post mortem. Increasing crowding for 3 h caused a significant drop in muscle pH and the time until onset of maximum rigor tension was reduced to 6 h post mortem. We conclude that optimum electrical stunning performs equally well as percussive stunning and that future challenges for improving the pre rigor times for Atlantic salmon lays in the pumping and crowding conditions, and not in the selected stunning technique.