I had a great opportunity to spent four weeks (23rd April – 22nd May) in “University of León - Universidad de León, INDEGSAL“, Spain, León. During these days I was working under supervision of PhD Felipe Martínez-Pastor. I have been studying methods of sperm motility analysis (CASA and CASA-automated plugins for ImageJ) and cluster (subpopulation) analysis of obtained data using R environment software (R-Studio). Dr. Felipe taught me how to adapt aforementioned plugins for the analysis of video records which we recorded in Czech Republic (records of whitefish and sturgeon spermatozoa). Also he explained theoretical basics of cluster analysis and how to apply it (using the R-Studio software) for the analysis of the data from plugins (several motility parameters for each spermatozoon). Obtained results showed very nice clusterization of whitefish spermatozoa in different activation media. This stay was supported from GAJU project (GAJU 062/2015/Z Fedorov).