A Body Volume Model for the Common Perch Perca Fluviatilis L., 1758

Background. Expansion of the digitalization possibilities in the modern scientific research aligns with the trends in societal development. The study of the body shape features of a fish contributes to collecting the primary material for further processing. The species-specific morphometric characteristics provide the means to derive a model from the original. Relevance. The improvement of methodological approaches to the creation of digital models in ichthyology and fish farming is crucial for expanding the possibilities of studying fish biology. The aim of this work is to substantiate the methodological approaches to the introduction of a digital model for a fish species using the common perch Perca fluviatilis L., 1758 as an example. Methods. The collection of primary material has been carried out according to conventional methods of ichthyological research. The volume of a fish body has also been studied through the example of a body shape model based on the collected morphometric data in the form of the sum of two halves of two ellipsoids. The possibility of using morphometric characteristics for creation of a “morphological passport” of a fish species has been investigated. Results. The ratio of the measured body volume of a common perch to the calculated volume according to the model featuring the sum of the halves of two ellipsoids has been identified. Based on the obtained values, it has been found to be close to 0.97, which is compliant with the investigated model by 97 % and determines the development of the common perch in the Dnieper-Bug Canal within the Pinsky District, Republic of Belarus. The rationale for using a non-specific data presentation for a fish species with the common perch as an investigation target is given based on the length from the end of its snout to the end of its scale covering. Following the results of this study, it has also been found out that the percentage values regarding l1/l in the common perch fingerling changed as compared to those of seven-yearling from 25 % to 17 %. However, the investigated O/l ratio increased from 43 % in fingerlings of this species to 50 % in older age groups. Conclusion. The sum of the ratios of the common perch body length taken from the top of the snout to the vertical line drawn from the base of the ventral fins to the dorsal fin, as well as its body width, height, and girth, to the length of its body from the top of the snout to the end of the scale covering has been identified. It started with 1.218 in fingerlings and increased to 1.926 in seven-yearlings. This unique combination of the four values of the investigated relationships can be used in creating a digital “morphological passport” of the common perch.