Effect of slaughter method on the progress of rigor of rainbow trout (Salmo gairdneri) as measured by an image processing system

Summary Rainbow trout (Salmo gairdneri) were slaughtered by AC and DC electrocution, exposure to elevated concentrations of carbon dioxide and by a blow to the head. The fish were subsequently bled and placed in ice. At regular intervals after slaughter the fish were taken from the ice and placed on a horizontal table with the posterior half of the fish overhanging the edge. The angle which the fish's tail formed with the vertical was used as an index of rigor and was measured by an image processing system. It was found that the stages of rigor were statistically the same for the four different treatments except that the onset of rigor for fish given a blow on the head was delayed.