Absence of rapid eye movements during sleep in adult zebrafish

•Zebrafish are novel yet important model in sleep research.•Sleep in zebrafish is measured using behavioral assays that cannot differentiate between REM and NREM sleep.•In current study we use image analysis to measure two key REM components: rapid eye movements and respiratory rate.•We show that there are no sleep related eye movements but during sleep respiration becomes slower and less regular.•We find no evidence for REM–NREM cycles in zebrafish.