Interactions among Size-Structured Populations in a Whole-Lake Experiment: Size- and Scale-Dependent Processes

• DOI: 10.2307/3547005
• Publication Date: 2007-02-02T17:42:14Z
• Authors: Lennart Persson; Par Bystrom; Eva Wahlstrom; Jens Andersson; Joakim Hjelm
• Keywords: Rutilus; Percidae

Interactions in size-structured populations are characterized by a mixture of predatory and competitive interactions dependent on the size individual organism. We analyzed this for species constellation consisting perch (Perca fluviatilis) roach (Rutilus rutilus) replicated whole lake experiment over 4 yr. Roach preyed upon large perch, but at same time compete with small zooplankton. Predictions regarding effects performance resource dynamics whole-lake were based results from previous pond enclosure experiments carried out short (months) periods. Variables measured included both level parameters (diet growth perch) as well population (mortality, numbers structures abundance biomass zooplankton benthic macroinvertebrates). The ≥ 2 yr old decreased to less than 10% pre-treatment levels treatment lakes after introduction remained low study period. mortality one-year-old older increased size. Larger had higher decrease smaller also rate young-of-the-year (YOY) was lower control lakes. YOY almost excluded during winter spring following introduction. few year class that survived years corresponding This could be related an availability predator-sensitive macroinvertebrates Perch fed larger extent pelagic As expected, abundances introduction, thereafter due absence recruitment these No incidence predation recorded attribute spatial scale escape ability habitat use vulnerable classes roach. stronger impact between-year variation can foraging (handling) capacity former restricted latter. Individual (diet, growth) statistical power (abundance, biomass, mortality), small-scale successfully predicted proportion (81%) parameters. However, success predicting responses (38%) directly connected failure predict (large diet growth). Our suggest major limitation predictive experiments.