Infestation of Argulus Foliaceus L. on Fish Fry Reared in Illuminated Cages

The rearing of fish fry in illuminated cages is one of the methods used before fish release into water bodies. The aim of the study was to investigate the peculiarities of infestation with Argulus foliaceus L. of the fry of pike Esox lucius (L.), pike-perch Sander lucioperca (L.), bream Abramis brama (L.), vimba Vimba vimba (L.) and peled Coregonus peled (Gmel.) reared in illuminated cages. The experiment was carried out in a mesotrophic lake in MayAugust. The fry of different fish species were reared in a separate net cages. Their density reached 10000 ind. m. A. foliaceus was detected on all fish fry species investigated. Infestation of fish with this parasite started when the total length of fish reached 1.8–2.0 cm. Correlation between the prevalence of Argulus and the total length of fish fry (r = 0.96, p = 0.049) and water temperature (r = 0.95, p = 0.045) was found to be reliable. The prevalence of this parasite was higher on peled than on bream (t-test = -5.748, p = 0.029) and vimba (t-test = -5.167, p = 0.035) of the same length. At the end of rearing period 0.01% of pike, 0.3% of bream, 1.4 % of vimba, 14.9% of pike-perch and 77.8 % of peled fry were infected with A. foliaceus.