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Against the flow: chemical detection of downstream predators in running waters

  • Jonas Dahl
  • Anders Nilsson
  • Lars Pettersson
Publishing year: 1998
Language: English
Pages: 1339-1344
Publication/Series: Royal Society of London. Proceedings B. Biological Sciences
Volume: 265
Issue: 1403
Document type: Journal article
Publisher: Royal Society

Abstract english

In running waters, chemical cues have generally been assumed to always come from upstream locations.

Here, we present ¢eld and laboratory evidence that Gammarus pulex can use chemical cues from down-

stream predators to adaptively adjust drifting behaviour. In the ¢eld, signi¢cantly fewer Gammarus

migrated into stream enclosures where brown trout (Salmo trutta) were present than into control enclo-

sures. In a subsequent laboratory experiment, Gammarus actively avoided live trout and trout chemicals

placed downstream in an arti¢cial stream, whereas no e¡ects were found in response to control or visual

cues.We suggest that the mechanism explaining the ability of Gammarus to detect downstream predators is

use of back£ows, which locally transport ¢sh chemicals against the main £ow. Such back£ows are both

created by the Gammarus itself and by surrounding substrate heterogeneity. These results profoundly a¡ect

the way in which we view the chemical environment of running waters and have important implications

for empirical and theoretical work evaluating predator e¡ects in running waters, as they demonstrate that

prey immigration rates can depend on downstream predator densities.


  • Ecology
  • chemical communication
  • predator^prey interaction
  • £uid dynamics
  • drifting behaviour
  • migration
  • Gammarus pulex


  • ISSN: 1471-2954
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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