VANN: Linking spatial breeding behaviour and population productivity in Atlantic salmon

Traditional coarse-scale analyses of population dynamics assume that individuals in a cohort experience identical densities. Yet, juvenile density is commonly influenced by the mother's decision on the spatial location of reproduction. Thus, behavioural d ecisions taken during reproduction may induce spatial variation in intensity of density dependence, and ultimately the productivity of populations. Furthermore, reproductive behaviour determines the habitat characteristics of emerging juveniles, and depen ding on dispersal abilities the availability of suitable habitats. Thus, there is a clear requirement for further advances in our understanding of how maternal behaviour may influence population productivity through effects on both abiotic and biotic envi ronments experienced by the resulting juveniles. In the present project we will quantify how spatial decisions taken by Atlantic salmon mothers during reproduction influence variation in reproductive success, and how the sum of such decisions within a pop ulation influences its productivity. More specifically, we will use studies of natural populations to test how productivity may vary among populations and within populations over time relative to the spatial dispersion of spawners. Furthermore, we will te st how the distribution of spawners relates to availability of breeding habitats and population density and if there is selection against spatial aggregation during breeding. Finally, we will examine how the total amount and the spatial distribution (rela tive to breeding grounds) of a potentially limiting juvenile resource (shelters) influences productivity. These studies complement smaller scale experimental work that has focussed on causal mechanisms, and will give broader insights into how important th ese issues are for productivity of natural Atlantic salmon populations.