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In the rudd aged two years and infected with Ligula intestinalis plerocercoids the relation between its body weight and lenght (longitudo corporis) was described as W=0.0129xL. The analogous relationship in healthy fish was W=0.0166xLAt a relative infection intensity of 7.99 per cent, the infected fish were about 29.5 per cent lighter than the healthy ones. The difference between the mean body length of infected and healthy fish was not significant (p<0.05). The infection occured mainly in early spring. Plerocercoids showed a regular increase of weight during the year. An average infection extensiveness was 31.6 per cent and it underwent seasonal changes with vertices in early summer and autumn. Fish infected with more than one plerocercoid displayed an increased death rate in summer months.
A parasitological study of 68 fishes belonging to seven species was conducted in July 2009. The fish species included the following: bleak, Alburnus alburmus (L.); roach, Rutilus rutilus (L.); rudd, Scardinius erythrophthalmus (L.); bream, Abramis brama (L.); ruffe, Gymnocephalus cernuus (L.); bullhead, Abramis bjoerkna (L.); gudgeon, Gobio gobio (L.). The aim of the study was to analyze the parasites of fish from Lake Wymój. A total of 16 parasites species belonging to the following taxa were identified: Monogenea (Dactylogyrus minor, Gyrodactylus sp., Paradipiozoon homoion homoion), Digenea (Diplostomum sp., Ichthyocotylurus platycephalus, Posthodiplostomum cuticola, Rhipidocotyle sp., Tylodelphys clavata), Cestoda (Caryophyllaceus laticeps, Paradilepis scolecina, Protocephalus sp.), Nematoda (Camallanus lacustris), Crustacea (Argulus foliaceus, Caligus lacutris, Ergasilus sieboldi), Mollusca (glochidia). Of all the parasites collected, the most frequent group was the metacercaria Diplostomum sp., the pleurocercus Paradilepis scolecina occurred less frequently, and the rest of the parasite species occurred rarely.
The column and thin-layer chromatography was used to the presence and total amount of carotenoids in some body parts of 5 fish species.
e paper presents results of a comparative analysis of two mathematical models of fish length growth: the von Bertalanffy equation and the modified power function. The accuracy of mathematical modelling of empirical data and a potential for extrapolation of theoretical growth range beyond the empirical data are compared. The data on accuracy and extrapolation potential, obtained with the two models tested and averaged for a species, were subject to the Student′s t test. Additionally, an attempt was made to determine a relationship between accuracy and extrapolation potential of each model; linear regression was used to describe the relationship. The generalised (ignoring between-specific differences) description of the relationship involved exponential, logarithmic, and power regressions in addition to linear regression.
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