Biology session

Morphometric methods that describe hard-to-define body shapes using mathematical methods are also widely used in biology. Among others, morphometrics is also used in fish biology, for example to characterise certain species or to separate fish stocks. The original objective of our study was to investigate the population structure of the European perch (Perca fluviatilis) stock in Lake Balaton based on morphological and morphometric characteristics. However, based on preliminary analyses, it appears that the person’s experience may have a significant influence on the results. Thus, the first focus of our study was to explore this methodological problem. Therefore, this methodical study’s aim is to examine how the results of morphometric measurements taken by measurers with different levels of experience will differ. By repeating the measurements several times, we also investigated the learning process and experience acquisition of each measuring person. The data were provided by six measurers with varying degrees of experience in morphometric measurements. The analyses were carried out on photographs of 80 perch from three populations using traditional distance-based morphometric method. In total, 21 morphometric variables were recorded on each photo by the measurers. These series of measurements were repeated three times. Preliminary results show that the results of the participants differ significantly from each other, and that the reliability of the measurements (the standard deviation of the data series) is significantly influenced by the experience and skill of the person taking the measurements and the quality of the images. However, analysis of the data series from the different persons showed similar patterns of separation in most of the three populations studied. It seems that the method can be used to isolate populations even by less experienced measurers. However, when comparing the data sets of different measurers, it is important to keep in mind that the results are fundamentally influenced by the measuring person.