Abstrakt
Individual growth plays fundamental role in brown trout population dynamics (Elliott 1994, Lobon-Cervia 2007). In our study, growth of brown trout individuals from original populations of headwater streams was observed in the Vydra and Kremelna river basins, Sumava National Park, Czech Republic.
The Sumava National Park is an important European biodiversity center, and one of the largest original natural areas in the Central Europe. Twenty localities were sampled by electrofishing twice in a season (May, October) during seven consecutive years (2005 - 2011).
In total, 5195 individuals of the brown trout were caught, measured, marked (VIA and VIE tags; NMT, Inc.) and released over this period. Scale samples were taken from 750 of them.
Fish growth was analyzed based on the scale reading, and verified by an increase in fish length of recaptured individuals. Average annual growth was 51 mm (range from 46 to 56 mm).
Fish growth was unbalanced as individuals grew more in summer period from June to September, and juveniles grew faster than adults. For more precise description of individual growth pattern was estimated space structure of the population by synchrony in demographic parameters among twenty observed sampling sites (Koizumi et al. 2008).
Growth was subsequently described in every synchronized population unit. Despite relatively low growth rate, typical in mountain steams populations, significant differences in individual body growth were found among estimated population units.
We believe that considering of population spatial structure in the management of natural brown trout populations can enhance effectiveness of its protection.