Impact of the riverbed morphology on the source of organic material and the trophic structure of fish community along the upper reaches of the Nevėžis River, Lithuania

L Čivas,V Kesminas,R Barisevičiūtė

doi:10.3750/aip2016.46.4.04

Abstract

Impact of the riverbed morphology on the source of organic material and the trophic structure of fish community along the upper reaches of the Nevėžis River, Lithuania

Highlights

Many rivers and streams have been channelized for various purposes
The presently reported study was intended to explore the possible effects of the riverbed morphology and agricultural activities on the chemistry and stable isotope composition of three main fish species: perch, Perca fluviatilis; roach, Rutilus rutilus; and pike, Esox lucius
To illustrate isotopic variation in size, perch, roach, and pike specimens were subsequently classified into length classes I and II (Table 2)

Summary

Introduction

Many rivers and streams have been channelized for various purposes. Channelization reduces the heterogeneity of physical habitats in rivers and streams (Bis et al 2000, Pliūraitė and Kesminas 2010) and is the most significant threat to the biodiversity and functioning of the river ecosystems worldwide (Rosenberg et al 2000, Nakamura and Yamada 2005).Stable isotopes are a useful tool for quantifying the energy and nutrient flow in ecosystems (Fry 2006, Jardine et al 2006). When using stable isotopes in ecological research, the most common elements are carbon ratios (13C ÷ 12C), whose isotopic signatures reveal the source material, and nitrogen ratios (15N ÷ 14N), whose signatures reflect the trophic position of animals (Post 2002). The presently reported study was intended to explore the possible effects of the riverbed morphology and agricultural activities on the chemistry and stable isotope composition of the three main fish species. In the study sites on the Nevėžis River, algal carbon isotope ratios were more 13C- depleted than those from terrestrial sources. The presently reported study revealed impact of abiotic habitat variables indicating the importance of physicochemical and morphological characteristics on δ13C and δ15N isotopic values variance of fish at natural and regulated river sites. The results could be useful for fisheries, i.e., impact of environmental factors on fish nutrition and growth

Objectives

Methods

Results

Conclusion