Modelling the complete life-cycle of Atlantic salmon (Salmo salar L.) using a spatially explicit individual-based approach

In this paper, we present a spatially explicit individual-based mechanistic model for predicting the freshwater population abundance of Atlantic salmon (Salmo salar L.). The model simulates the complete life-cycle at small spatial (∼50 m) and temporal (weekly) scales. Processes such as spawning, recruitment, mortality and movements are predicted using deterministic and stochastic functions, parameterized using relationships established from the literature and empirical observations. The model was used to simulate salmon population abundance within a river in western-central Norway (River Nausta). The sensitivity of population abundance to fry and parr carrying capacities, and parr and post-smolt density-independent mortalities was analyzed. The optimally parameterized model predicted similar abundances and age compositions across the developmental stages of the population to those estimated from empirical observations within the river. The effect of carrying capacities and mortalities on abundance was strongest at the developmental stage at which they operated, but also affected the abundance of subsequent developmental stages or the progeny, suggesting negative (dampening) feedback mechanisms.