The total time for passage of food through the gut until the non-digestible portions of a meal are voided as faeces has not commonly been measured. Gastric emptying time and total passage time in skipjack tuna at 23-26 C was about 12 hours with the intestine being maximally filled about five hours after eating and empty after about 14 hours. Defaecation often occurred 2-3 hours after a meal, presumably being material from a previous meal. After a single meal, faeces were found 24, 48 and even 96 hours after the meal. Thus, there is considerable variation in food passage time, presumably relating to the digestibility of the food. Magnuson (1969) commented that the passage rates in skipjack tuna were at least twice as fast as known for any other fish.