Thrond HaugenUniversität Oslo |
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The role and interplay of density-dependent and density-independent processes in pike population biology: tales from long-term mark-recapture data in windermere |
| Quantifying effects of density-dependent and density-independent factors in demographic and dispersal processes are key topics in population ecology. Based on long-term mark-recapture data (1949–2000) on pike (/Esox lucius/) from Windermere, we provide estimates of density-dependent and density-independent effects on natural survival, growth and dispersal. Multistate mark-recapture analyses of the data revealed pronounced within-lake spatial differentiation (basin level) in both density-dependent survival and dispersal. By using the estimated density-dependent survival, fecundity and dispersal functions for pike larger than 55 cm fitness landscapes as function of pike density in the two basins could be assessed. The intersection area between the two fitness landscapes corresponds to the ideal-free-distribution (IFD) densities. Historical observations of large-pike distributions showed high accordance with the predicted IFD. In small pike (<55 cm), summer water temperature was shown to modulate density-dependent mortality, and also individual growth: at low temperatures survival was lowest at high small-pike abundances and low perch (prey) abundances; at low temperatures, survival was lowest at high small-pike abundances and high perch abundances. An individual growth analysis also indicated that cannibalism may be biased in favour of rapid growth for the surviving individuals. However, a recent experimental study demonstrates that profound population-level consequences can result from even nonconsumptive and nonlethal effects of social stress in this species. Due to the strong effect of individual size on survival and fecundity found in pike, any factor affecting the individual growth process may therefore impose significant population-level consequences. |
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Ort |
| 10.12.2009 16:00 Uhr Großer Hörsaal |
© IGB |