Burnt Tuna: An Ultrastructural Study of Postmortem Changes in Muscle of Yellowfin Tuna ( Thunnus albacares ) Caught on Rod and Reel and Southern Bluefin Tuna ( Thunnus maccoyii ) Caught on Handline or Longline

ABSTRACT Ultrastructure of muscle from yellowfm tuna ( Thunnus elbacares ) caught by rod and reel, and southern bluefin tuna ( Thunnus maccoyii ) caught by longline or handline was examined at various postmortem times. The pattern of degeneration after death was similar to that of other vertebrates. Burnt tuna meat, which is pale or brown in color, and soft, occurred in carcasses showing a greatly accelerated rate of postmortem degeneration. Burnt tuna had no ultrastructural features which made it different from normal degenerated meat. Ultrastructural quality of muscle was best in samples from longline tuna, and poorest in samples from handline tuna. Longer capture times (hooking to boating) are correlated with better ultrastructural quality of tuna meat, and less burning.