The crayfish are widely accepted as very sensitive and fast bio-indicators of changes in water quality. Studies based on heart beat analysis demonstrated the potential of using crayfish as detector of pollutants. Consequently, several computer-aided systems were developed to use this mechanism. The main complication with applying such a system is the necessity of using metal wires or optical fibres to transmit the signal from sensor which is placed on back of the crayfish to the processing hardware; these attachments restrict system design to one crayfish in one aquarium.

The multidisciplinary collaboration of the two laboratories (Laboratory of Signal and Image Processing and Laboratory of Ethology of Fish and Crayfish) led to an original system for crayfish heart beat monitoring based on completely non-invasive/contactless hardware. The system can determine crayfish heart beat frequency using only the combination of near infra-red (NIR) illuminator and sensitive camera. The heart rate is the only parameter needed in most of the studies using crayfish as bio-indicators. The low-cost system needs no attachment, so more crayfish in one aquarium can be monitored simultaneously and it provides accurate information on heart rate and crayfish need no adaptation to the system. It can be used as equivalent to existing systems to simplify the crayfish studies.

Detailed information on obtained results can be found in publication: Císař, P., Saberioon, M., Kozák, P., Pautsina, A., 2018. Fully contactless system for crayfish heartbeat monitoring: Undisturbed crayfish as bio-indicator. Sensors and Actuators B: Chemical 255: 29-34. (IF 2016 = 5.401; AIS 2016 = 0.786).

- Top image – raw image of infrared camera, white rectangles represent reflective markers of around heart area, red rectangle is determined by the software automatically and visualized to the image.
- Bottom image – the changes of reflected infra-red light from the heart area (red rectangle) with detected local minima and maxima representing crayfish heart rate.