Long-term examination of health conditions in monoculture of communally tested amphimictic diploid, diploid gynogenic and triploid tench, Tinca tinca (L.)

Abstract

Amphimictic diploid (2n), induced triploid (3n) and meiotic gynogenic (MeiG) tench populations were established in 1998 by mass propagation. After separate nursing, fish were group-marked by freeze branding and 200 specimens per population were stocked into an experimental earthen pond for communal test until present. Parasitological and haematological (haemoglobin content Hb, haematocrit PCV and differential leukocyte count) examinations were performed every spring and autumn in the 2+ category, once sex could be registered macroscopically. Altogether 9 genera and/or species of parasites were detected on skin, 7 genera and/or species on gills, 1 genus in eye and 1 species in gut. The highest invasion extensity was recorded in the MeiG tench in the majority of examinations till the age of 4+. The courses of PCV and Hb values for 2n and MeiG populations showed high similarity while those for 3n population were slightly decreased and sex-related differences proved to be insignificant within populations in the majority of examinations. Differential leukocyte counts showed significant differences (p<0.05) of 3n vs. 2n and/or MeiG considering lower proportions of lymphocytes and higher proportions of segmented neutrophils in the majority of cases.