Gut residence time (GRT) is often reported to be extremely variable among crustaceans. In this study, GRT was measured in tethered mysids that were fed continuously, and appearance of the first faecal pellet was found to be quite consistent averaging 1.6 h. There was no significant difference between GRT in those mysids held singly and those accompanied by free-swimming conspecifics, even though previous studies have shown metabolic benefits in social behaviour. Gut residence time data from a range of pelagic crustaceans feeding continuously showed a clear linear relationship with size. It appears that, when feeding ceases and crustaceans are allowed to clear their guts in filtered water, GRT can be very long and variable. However, when feeding is continuous, GRT can be relatively short and consistent.
