ABSTRACT. – This review article deals with possibilities and ways of using comparati-
vely simple hematological methods in evaluation of fish welfare and health. A broad over-
view of data concerning these topics was given. Special emphasis was put on a number of
influences affecting hematological status. They include life cycle phase, biological rhythms,
environmental impact, feed quality, pathogens and stress. It is stressed that knowledge of
above influences is a prerequisite to distinguish physiological from patholocical blood
picture. In the same time, they are essential to establish normal values for a given species.
A brief outline of basic, easy applicable, hematological methods was also given. The use
of hematological status in evaluation of fish welfare and health was illustrated by two case
studies. As a conclusion, use of hematological analyses is recommended in fish culture
and environmental research.
