Abstract
Observations were conducted of the changes in the measurements of selected morphometric characters in embryos and larvae of three closely-related fish species (dace, Leuciscus leuciscus (L.), ide, Leuciscus idus (L.), European chub, Leuciscus cephalus (L.)). It was confirmed that individual development immediately following hatching is fast with rapid changes in body proportions that stem from the development of particular systems. It was also observed that in dace and ide the values of the biometric characters observed were very similar, as were the trends of these changes. Although chub differed insignificantly from the other two species, statistically significant relative values and the character of growth were noted especially with regard to the lowest height of the tail fold, head depth, body depth, and yolk sac length. Differences in body proportions can be explained by the different maintenance strategies of these species during the earliest stages of ontogenesis.