Aquatic Sciences

, Volume 78, Issue 4, pp 641–654 | Cite as

The scales of variability of stream fish assemblages at tributary confluences

  • I. Czeglédi
  • P. Sály
  • P. Takács
  • A. Dolezsai
  • S. A. Nagy
  • T. ErősEmail author
Research Article


Tributary confluences play an important role in the dispersal of organisms, and consequently, in shaping regional scale diversity in stream networks. Despite their importance in dispersal processes, little is known about how ecological assemblages are organized in these habitats. We studied the scales of variability of stream fish assemblages over three seasons using a hierarchical sampling design, which incorporated three tributaries, three sites at the mouth of each tributary and using four sampling units at each site. We found strong scale dependent variability in species richness, composition and relative abundance. Most of the variation was accounted for by the interactive effect of season, between stream and between site effects, while habitat structure of the sampling units had a relatively minor role. Species richness showed a continuous decrease from the mainstem river in most cases, while species composition and relative abundance changed less consistently along the longitudinal profile. Consequently, we found that not only the junctions presented a strong filter on the species pool, but some species were filtered out if they passed this critical habitat bottleneck. In addition, spatial position of the tributaries along the river also contributed to assemblage variability in the confluences. Overall, our results suggest high variability in fish assemblages across multiple scales at tributary confluences. Environmental management should take a more critical care on the filtering role of tributary confluences in species dispersal, for better understanding patterns and processes in the branches of dendritic stream networks.


Stream networks Tributaries Ecotones Habitat bottlenecks Environmental filtering Dispersal 



We would like to express our thanks for the numerous people who helped in the field work including Zoltán Vitál, András Specziár, Árpád Ferincz, Gergely Erős, András Erős. This work was supported by the OTKA K104279 grant and the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (Tibor Erős). The work of István Czeglédi was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP 4.2.4. A/2-11-1-2012-0001 ‘National Excellence Program’.

Supplementary material

27_2015_454_MOESM1_ESM.ppt (415 kb)
Distance decay relationships in fish assemblages at the habitat unit level (i.e. all units are compared within and between streams) for each season separately using the Jaccard and the Bray–Curtis dissimilarity indices for species composition and relative abundance data, respectively (PPT 415 kb)


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Copyright information

© Springer International Publishing 2015

Authors and Affiliations

  • I. Czeglédi
    • 1
  • P. Sály
    • 2
  • P. Takács
    • 2
  • A. Dolezsai
    • 2
  • S. A. Nagy
    • 1
  • T. Erős
    • 2
    Email author
  1. 1.Department of HydrobiologyUniversity of DebrecenDebrecenHungary
  2. 2.MTA Centre for Ecological ResearchBalaton Limnological InstituteTihanyHungary

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