Longitudinal structure of fish assemblages in a minimally disrupted stream

Abstract

Abstract:The longitudinal distribution patterns of fish species are affected by both natural and anthropogenic variables. The role of these factors on the formation of species assemblages is well documented in North America and Western Europe, but detailed information is lacking from Central and Eastern Europe, and the Carpathian region especially. Therefore, we examined the structure of fish assemblages in response to six key environmental parameters in a natural stream system (Udava stream basin, Slovakia). We used the indirect ordination method of gradient analysis (Detrended Correspondence Analysis, DCA) to analyse the species groups and their connections to the sampled sites and to recognize the strongest gradient of assemblage composition. Subsequently, we used the direct ordination method (Canonical Correspondence Analysis, CCA) to identify the strongest gradients in relation to selected variables. Two major gradients were identified that follow the upstream-downstream pattern of fish communities and three variables (distance from source, depth and site slope) are correlated with the first CCA axis (P < 0.05) and two variables (depth and vegetation cover) are correlated with the second CCA axis (P < 0.05). We assume that these factors influence the temperature and the amount of dissolved oxygen that can cause oxygen and temperature stress to intolerant species (e.g., salmonids). Based on these results, we assume that the economically important species, brown trout and grayling, are not native to the stream basin and this status is only the consequence of natural factors. Furthermore, the results suggest that the Udava stream offers favourable conditions for fish species distribution -a view supported by the high variability of particular variables within the proposed model.

Diversion of Fishing Pressure on the Economically Important Species Barbus barbus (Linnaeus, 1758) to Protect the Community Interest Congeneric Barbus meridionalis Risso 1826, Based on a Decision-Support Management System

“…The Carpahians basin are under constant pressure due to overfishing, including poaching (Curtean- Florea, 2011;Pekárik et al, 2011;Guti, 2014;Didenko et al, 2014) and the Târnava Basin is not an exception in this respect (CurteanBănăduc and Bănăduc, 2007) a basin where live many protected fish species, Barbus meridionalis Risso 1826 being one of them. This species is terra typical to the Mureș River in which Târnava River is flowing, in the studied lotic sectors it is living sometimes together with its congener species Barbus barbus (Bănărescu, 1964;Bănărescu and Bănăduc, 2007).…”