Nocturnal feeding patterns of <i>Mysis relicta</i> in Lake Michigan, based on gut content fluorescence1

Abstract

Fluorometric measurements of the gut contents of Mysis relicta were used to determine the relative amount of pheopigment per animal at 0.5, 3.5, and 6.5 h after sunset. Mysid guts always contained significantly greater relative amounts of pheopigments at 3.5 than at 0.5 h after sunset; changes between 3.5 and 6.5 h after sunset were less consistent. This is taken to indicate that mysids filter feed on phytoplankton throughout their summer diel vertical migrations in Lake Michigan.