Demands of aquatic products are increasing dramatically during past decades. Also quality assurance has gradually received more attention by both producers and consumers. Thus, fish producers are exploring all possible approaches for improving the productivity and profitability. Monitoring of fish state and behaviour during cultivation may help to improve profitability for producers and also reduce the threat of severe loss because of disease and stress incidents. It is necessary to evaluate and measure quality of fish products in accurate, fast and objective way for meeting the different demands of the fish‐processing industry after harvesting. Traditional methods are usually time‐consuming, expensive, laborious and invasive. Using rapid, inexpensive and noninvasive methods is therefore important and desirable. Optical sensors and machine vision system provide the possibility of developing faster, cheaper and noninvasive methods for in situ and after harvesting monitoring of quality in aquaculture. This review describes the most recent technologies and the suitability of different optical sensors for the fish farming management and also assessment, measurement and prediction of fish products quality. Two major areas of optical sensors applications in aquaculture are discussed in this review: (i) preharvesting and during cultivation; and (ii) post‐harvesting. Finally, accuracy and uncertainty of optical sensors applications in aquaculture are discussed. This review showed that MVSs and optical sensors have found real‐world application based on tremendous possibility offered by digital camera development and increasing the speed of computer‐based processing; however, still new algorithms, methods and re‐engineered sensors need to be developed to meet real‐world requirements.

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Crayfish cardiac activity monitoring and analysis are widely used during water pollution and ethological studies. A noninvasive crayfish cardiac activity monitoring (NICCAM) system discussed in the current study permits long-term, continuous monitoring of several crayfish simultaneously. The advantages of the system are low price, low number of required components and the possibility of cardiac signal shape monitoring. Calculation and analysis of parameters characterizing the shape of the double peak cardiac activity allows not only reducing the number of incorrect peak detections improving the system accuracy but also can provide additional information on crayfish state. The discussed preliminary experiments on the effect of food odor and chloramine-T on crayfish showed promising potential of signal shape analysis for studying of crayfish cardiac reaction to changes in the aquatic environment.