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Interspecific competition and predation: relative effects on foragers and their densities

  • Erika Nilsson
  • Anders Persson
  • Anders Nilsson
Publishing year: 2010
Language: English
Pages: 729-736
Publication/Series: Behavioral Ecology and Sociobiology
Volume: 64
Issue: 5
Document type: Journal article
Publisher: Springer

Abstract english

Predation and competition are both strong structuring forces in community dynamics, but their relative importance is disputed. In a laboratory experiment, we evaluated the relative importance of competition and predation from juvenile and adult brown trout, respectively, on foraging performance of groups of three stone loaches. We observed loach consumption rate, time spent inactive, and aggressive interactions between juvenile trout and loach in artificial stream sections. The controlled experiments were complemented by examining stone loach population densities in natural systems as functions of juvenile and adult trout. In the laboratory experiments, increasing numbers of competitors decreased prey availability, which ultimately led to lower consumption rates for loach. Loach responded to predation risk by increasing time being inactive, thereby decreasing consumption rates. However, there were no effects of juvenile trout competitors on loach consumption rates in treatments with adult trout presence, suggesting no additive effect of predation and competition on loach foraging success. Partial regressions of loach and trout densities in natural streams revealed a positive relationship between juvenile trout and loach, and a negative relationship between adult trout and loach. Our laboratory and field data thus suggest that predation is a limiting factor for loach success, and predator presence could mediate species coexistence at high interspecific densities.


  • Ecology
  • Salmo trutta
  • barbatula
  • Barbatula
  • Fish
  • Predation
  • Foraging
  • Interspecific competition


  • ISSN: 1432-0762
Anders Nilsson
E-mail: anders [dot] nilsson [at] biol [dot] lu [dot] se


Aquatic ecology

+46 46 222 83 65

+46 70 346 25 66



Research group

Aquatic Ecology


Doctoral students and postdocs

Main supervisor

Varpu Pärssinen

Assistant supervisor

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