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Abundance of the barbel, Barbus barbus in the river Jihlava
Peňáz, Milan ; Pivnička, K. ; Prokeš, Miroslav ; Baruš, Vlastimil
A four-year experiment with a total of 993 individually tagged barbel, Barbus barbus, resulted in the assessment of survival and abundance. The Jolly-Seber method was used to estimate abundance from autumn 1999 to spring 2001 (minimum 233, maximum 563 ind./ha). The mean annual survival rate was 0.862, but the partial values assessed separately for seasons (spring - autumn and autumn - spring) differed considerably and the possible reasons for this phenomenon are discussed. On the basis of known survival rate, the abundance was subsequently estimated (for the entire studied stretch and per hectare) using the Petersen capture-recapture method for the period spring 1999 to autumn 2001. Its mean values reached 303 +- 110 ind./ha (minimum 195, maximum 498 ind./ha). These results were in autumn 2001 supported by another simultaneously conducted census following the removal method by Zippin (316 ind./ha).
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Concentrations of heavy metals and changes in concentrations of the mercury in muscle tissues of the barbel (Barbus barbus) from the river Jihlava
Peňáz, Milan ; Baruš, Vlastimil ; Prokeš, Miroslav
Heavy metsl concentrations were studied in muscles of barbel, Barbus barbus from three sites of the Jihlava River. Only low concentrations of eight elements (As, Cd, Hg, Pb, Cr, Ni, Cu, Zn), not exceeding the maximum permissible values, were found in four mixed samples collected on the site near Hrubšice (RK 46.0-49.1), with a relatively high water quality. Samples differed by the sex, size and age of the fish. Solely the mercury content was analysed on other two sites in the river Jihlava located upstream and downstream the effluents from the sewage plant of the Třebíč city (RK 89.5-91.0 and 85.0, resp.). The obtained values exceeded the maximum permissible value of 0.1 mg.kg-1 in all of 27 individually analysed specimens and averaged 0.208 and 0.187 mg.kg-1, resp., of fresh matter. A high capability of barbel to indicate the burden of aquatic ecosystems by heavy metals was emphasized.
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