Fishery-induced changes in vital components of a large pike (Esox Lucius) population

Phenotypes results from genetic, environmental and genetic * environment influences. Separating these causes of variation is a major topic in evolutionary ecology. Harvested populations provide a rare opportunity to investigate these affects since human-induced mortality adds a strong and measurable component to the natural selective forces shaping vital rates. To address these processes, we use the unique, long-term capture-mark- recapture and back-calculated length data on pike (Esox lucius) from Lake Windermere (UK) which has been gillnetted since 1944 for scientific purpose. The quality of this dataset allows us to robustly test assumptions about the constraints shaping pike life history including survival, growth and fecundity, taking into account environmental covariates such as temperature and pike and prey abundance. Parallel to this modeling part, we are running mesocosm experiments (at the NIVA’s research station of Solbergstrand) in which we manipulate pike density in excess- feeding conditions. The aim is here to quantify the impact of density on behaviour, endocrine status, growth and maturation (irrelative to food availability), and thus gaining insights into some of the mechanisms of density-dependence.