ABSTRACT

Lowering the body temperature close to freezing delays the onset of rigor. The duration of rigor is also a function of body temperature and glycogen content at death. A high glycogen content and a low temperature above freezing both serve to prolong rigor. Rigor mortis is of longer duration if the fish has exerted less muscular activity prior to death. This results in a higher glycogen content. Results of several studies demonstrated that rigor mortis developed earlier and disappeared sooner in trawl-caught fish compared to fish caught with hand lines. This was attributed to struggling, crushing, and anoxemia in the trawl-caught fish. It is also believed that the shorter the trawler haul is, the better the fish will keep. In any given catch of trawl-caught fish, some of the fish may still be alive when the nets are hoisted on deck; thus, there may be a variation among the fish in the amount or degree of struggle expended prior to death. This could account in part for the variability in keeping-quality within the same catch of fish. The onset and duration of rigor vary with different species. In general, flatfish exhibit a more extensive rigor than round fish.