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International Journal of Zoology
Volume 2012 (2012), Article ID 378913, 6 pages
http://dx.doi.org/10.1155/2012/378913
Research Article

Density-Dependent Habitat Selection in a Growing Threespine Stickleback Population

Department of Biosciences, University of Helsinki, P.O. Box 65, 00014 Helsinki, Finland

Received 19 March 2012; Revised 19 April 2012; Accepted 19 April 2012

Academic Editor: Thomas Iliffe

Copyright © 2012 Ulrika Candolin and Marita Selin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Human-induced eutrophication has increased offspring production in a population of threespine stickleback Gasterosteus aculeatus in the Baltic Sea. Here, we experimentally investigated the effects of an increased density of juveniles on behaviours that influence survival and dispersal, and, hence, population growth—habitat choice, risk taking, and foraging rate. Juveniles were allowed to choose between two habitats that differed in structural complexity, in the absence and presence of predators and conspecific juveniles. In the absence of predators or conspecifics, juveniles preferred the more complex habitat. The preference was further enhanced in the presence of a natural predator, a perch Perca fluviatilis (behind a transparent Plexiglas wall). However, an increased density of conspecifics relaxed the predator-enhanced preference for the complex habitat and increased the use of the open, more predator-exposed habitat. Foraging rate was reduced under increased perceived predation risk. These results suggest that density-dependent behaviours can cause individuals to choose suboptimal habitats where predation risk is high and foraging rate low. This could contribute to the regulation of population growth in eutrophicated areas where offspring production is high.