Review of Circadian Activity and Sleep Behavior in Fish and a Pilot Study

Abstract

Animals, including fish, regulate their activity and sleep patterns via an endogenous circadian clock. Sleep is a universal phenomenon across taxa, including humans, and it serves multiple functions such as neural recovery, metabolic regulation, and immune maintenance. However, sleep in fish is difficult to define solely based on behavior; therefore, physiological and genetic indicators have commonly been used in parallel to characterize sleep-like states. These investigations were conducted primarily in a laboratory setting using video-based tracking systems. In this study, methods for assessing fish activity and sleep were reviewed, and these approaches were applied to black and red seabream to evaluate their circadian activity patterns. Both the species exhibited stable daily activity rhythms under controlled laboratory conditions. These findings provide baseline information that can contribute to understanding the behavioral and physiological responses of aquaculture species to rising seawater temperatures associated with climate change, and to the development of appropriate management strategies.