SynopsisTo determine whether burbot occupy defined home range in rivers, we radio-tracked individuals in the Ohrˇe River, Czech Republic. We also tested the hypothesis that the size of burbot home range would correlate with the fish mass. BurbotÕs strong attraction to suitable refuges was the basis for our second hypotheses, that its diurnal behavior would reflect refuge availability in the riverine environment. To test these hypotheses, we analyzed data on fish movements in relation to depth, velocity, substratum size and river slope. During the night, burbot preferred deeper areas with lower slope and finer substrates than during daylight hours. The home range was smaller in areas with low or zero slopes, and significantly increased with increasing river slope. There was no relationship between home range size and fish mass. River slope appeared to be the main predictor of the burbotÕs home range size.

This paper examines the relationships between watercourse typology and selected indicators of long-term surface water quality for rivers in the Czech Republic. The parameters used to define watercourse typology are in accord with the Water Framework Directive 2000/60/EC outlined by the European Commission. The relationships were tested using descriptive and multivariate statistical analysis, namely cluster analysis and canonical correspondence analysis. It was found that only some of the typological parameters have a close association with indicators of surface water quality. Specifically, the parameters of altitude and geology show clear relationships with pH, calcium content, and the saprobity index of macroinvertebrates. Conversely, parameters that are strongly influenced by anthropogenic pollution show weak relationships with indicators of surface water quality. These depend instead on the presence of pollution sources rather than on natural environmental conditions.

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On the basis of the results of calibration of current meters at water of varying temperatures, a hypothesis that water temperature influences measured water velocities was formulated. The analysis of our long-term data showed that the water temperature does have an influence on measured water velocity. This influence can be taken into account for practical purposes as a contribution to the uncertainty of measurements. The influence depends on the type of current meter propeller. This paper presents results obtained for the Ott C-2 current meter with propellers of the types 1, 2, 3, 5 and 6. Our analysis showed that the uncertainty is equal or less than 5% for measurements carried out in water with temperatures above 8°C. The differences between measured water velocities for water temperatures 5°C and 20°C reached maximum 6% (depending on the propeller) in a slowly flowing water (rotational frequency n = 1 s -1 ). For rotational velocity n ≥ 2 s -1 the differences between velocities measured at water temperatures 5 and 20°C were mostly under 3%. The less influenced propeller is of type 3 for which the uncertainty of measurement does not reach 5% even for water temperature 1ºC if the rotational frequency is bigger than 0.7 s -1 .