| Popis: |
Objective: to characterize age-length composition of fish population in the lake Ozeryavki at National Park «Sebezhsky» and to estimate the density and biomass of main species using A method for estimating fish density through the catches of gillnets Methods: a method for estimating density by catches of gill nets applied to the catches of different mesh size.Methods: a method for estimating density by catches of gill nets applied to the current data.Novelty: estimates of mortality of 3 main species, roach, white bream and perch, in one of the lakes of the national park were obtained for the first time; the density and biomass of 3 species are calculated and the proportion of mortality from predation is estimated.Results: instantaneous natural mortality coefficients for roach, white bream and perch corresponds to Z = 0.59 year-1, Z = 0.51 year-1 and Z = 0.71 year-1, respectively; the general density of all age groups is: for roach 2.7 ind./m3, for white bream 0.9 ind./m3 and for perch 2.0 ind./m3; average biomass: for roach 14.3 g/m3, for white bream 4.5 g/m3, for perch 3.0 g/m3; mortality rate from pike predation accounts for 0.34 of biomass of three species.Conclusion. The study of fish population of lake Ozeryavki as a typical medium-sized reservoir in the Sebezhsky National Park gives an idea of local ichthyocenoses parameters and aquatic ecosystem condition as a whole. |
