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- Title
Interactions among size-structured populations in a whole-lake experiment: size- and scale-dependent processes
- Authors
Persson, Lennart; Andersson, Jens; Bystrom, Par; Hjelm, Joakim; Wqahlstrom, Eva
- Abstract
Interactions in size-structured populations are characterized by a mixture of predatory and competitive interactions dependent on the size of the individual organism. We analyzed this mixture of size-structured interactions for a species constellation consisting of perch (Perca fluviatilis) and roach (Rutilus rutilus) in a replicated whole lake experiment over 4 yr. Roach are preyed upon by large perch, but atthe same time compete with small perch for zooplankton. Predictions regarding the effects of roach on perch performance and resource dynamics in the whole-lake experiment were based on results from previouspond and enclosure experiments carried out over short (months) time periods. Variables measured in the whole-lake experiment included both individual level parameters (diet and growth of perch) as well as population level parameters (mortality, population numbers and size structures of perch, abundance and biomass of zooplankton and benthic macroinvertebrates). The population size of perch ? 2 yr old decreasedto less than 10% of the pre-treatment levels in treatment lakes after the introduction of roach and remained low over the whole study period. The mortality in perch one-year-old and older increased with size. Larger perch had a higher growth decrease than smaller perch, but also the individual growth rate of young-of-the-year (YOY) perch was lower in treatment lakes than in control lakes. YOY perch were almostexcluded during the winter and spring following the roach introduction. The few perch of this year class that survived had the following years a higher growth than the corresponding year class in control lakes. This could be related to an increased availability of predator sensitive macroinvertebrates in treatment lakes. Perch in treatment lakes fed to a larger extent on macroinvertebrates and less on pelagic zooplankton than perch in control lakes. As expected, zooplankton abundances decreased in treatment lakes the year following the roach introdu
- Subjects
ECOLOGY; POPULATION biology; PREDATION; ZOOPLANKTON
- Publication
Oikos, 1999, Vol 87, Issue 1, p139
- ISSN
0030-1299
- Publication type
Article
- DOI
10.2307/3547005