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The influence of productivity and width of littoral zone on the trophic position of a large-bodied omnivore.

  • Patrik Stenroth
  • Niklas Holmqvist
  • Per Nyström
  • Olof Berglund
  • Per Larsson
  • Wilhelm Granéli
Publishing year: 2008
Language: English
Pages: 681-690
Publication/Series: Oecologia
Volume: 156
Document type: Journal article
Publisher: Springer

Abstract english

Omnivory is common in many food webs. Omnivores in different habitats can potentially change their feeding behaviour and alter their trophic position and role according to habitat conditions. Here we examine the trophic level and diet of the omnivorous signal crayfish (Pacifastacus leniusculus) in gradients of trophic status and lake size, both of which have been previously suggested to affect trophic position of predators separately or combined as productive space. We found the trophic position of omnivorous crayfish to be positively correlated with lake trophic status, but found no evidence for any influence of lake size or productive space on crayfish trophic position. The higher trophic position of crayfish in eutrophic lakes was largely caused by a shift in crayfish diet and not by an increase in trophic links in basal parts of the food web. Hence, our results support the "productivity hypothesis," suggesting that food chains can be longer in more productive systems. Furthermore, stable isotope data indicated that larger crayfish are more predatory than smaller crayfish in lakes with wider littoral zones. Wider littoral zones promoted the development of intrapopulation differences in trophic position whereas narrow littoral zones did not. Hence, differences in habitat quality between and within lakes seem to influence the trophic positions of omnivorous crayfish.


  • Ecology
  • Trophic structure - Food chain length - Lake food webs - Stable isotopes - Crayfish


  • ISSN: 1432-1939
Wilhelm Granéli
E-mail: wilhelm [dot] graneli [at] biol [dot] lu [dot] se

Professor emeritus

Aquatic ecology

+46 70 279 82 34