Growth in length and weight, based on a combination of scale annulus interpretation and back-calculation using the Fraser-Lee model, was studied in male and female barbel, Barbus barbus, from a section of the River Jihlava sampled in 1999–2001. Results were compared with growth data obtained with similar methods in 1976, prior to construction and functioning of a hydropower scheme complex, and during the period of the scheme’s partial operation (1980–1984). Recent growth rate, under seemingly fully-stabilised environmental conditions and complete adaptation of the barbel population, showed the highest distinct sexual dimorphism in growth rate was also confirmed, with females growing faster than males, though to a lower extent than recorded both during previous periods and from several other localities. Further, upon comparison of back-calculated lengths for previous years of recently tagged-and-recaptured fish (1999–2001) with observed lengths directly measured at corresponding ages, no significant differences were overall found between the results obtained by either method in most age groups. Finally, the linear Fraser-Lee model proved a sufficiently accurate and practical method for back-calculating lengths for previous years of life also in barbel.
Altogether 701 adult barbel, Barbus barbus were captured by electrofishing and individually tagged to study their local displacement and movements in a stretch of the River Jihlava (Czech Republic). A total of 149 fish were recaptured and 105 of them (70.47 %) were considered as ”resident” because they were always recaptured in the same, relatively restricted (250 - 780 m) stream section, which always contained a pool and was demarcated naturally by riffles on both edges. The remaining 44 recaptured specimens (29.53 %) belonged to the “mobile” part of population, their movements encompassing two (or exceptionally more) adjacent stream sections and at maximum a distance of 1680 m downstream or 2020 m upstream. The proportion of mobile barbel, relatively low in smaller and middle size classes, increased in the largest size classes (451–550 mm of SL). A rather limited extent of movements also suggests a relatively small area of home range in the studied stretch, which nevertheless provides satisfactory resources and favourable conditions required by barbel over their entire life cycle. The extent of movements and corresponding proportion of mobile fish appear to be increasing with diminishing habitat patchiness. In the stretch of River Jihlava studied, with a rich patchy heterogenous habitat and well developed riffle-pool-raceway structure, each section (pool) can be considered as a more or less isolated spatial unit containing its own, and in a certain degree, isolated component of a metapopulation.
A four-year experiment with a total of 993 individually-tagged barbel, Barbus barbus, resulted in the assessment of survival and abundance. 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 2002, and the mean value reached 303 ± 110 ind.ha-1 (minimum 195, maximum 498 ind.ha-1). The Jolly-Seber method was also used to estimate abundance from autumn 1999 to spring 2001 and gave a mean 425 ± 120 ind.ha-1 and a range 233–563 ind.ha1. These results were in autumn 2001 supported by another simultaneously conducted census following the removal method by Zippin (316 ind.ha-1). The abundance showed a significant tendency to increase during the four-year survey, which is in an accordance with the long-term changes observed in the dynamics of the fish community in this stream.