University of South Bohemia in Ceske Budejovice 1 article published in JoVE Behavior Continuous Noninvasive Measuring of Crayfish Cardiac and Behavioral Activities Iryna Kuklina*1, Filip Ložek*1, Petr Císař1, Aliaksandr Pautsina1, Miloš Buřič1, Pavel Kozák1 1Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budĕjovice This article presents a noninvasive biomonitoring system for the continuous recording and analyses of crayfish cardiac and locomotor activities. This system consists of a near-infrared optical sensor, a video-tracking module, and software for evaluating crayfish heartbeats that reflects its physiological condition and characterizes crayfish behavior during heartbeat fluctuations.