Abstract

BISCAYART, Carolina  and  DE TORRES CURTH, Mónica I. Dynamic programming in migration processes studies. Ecol. austral [online]. 2009, vol.19, n.2, pp.93-105. ISSN 1667-782X.

Dynamic programming is an optimization process that allows obtaining a decisions sequence that gives an optimal solution of a problem in study. This work applies this tool to study the displacement of young salmonids during their stay in their natal stream. This displacement depends on their needs, according to their age and physical condition, but it is also related with the environment offer. Our objective was to model this process by mean of the dynamic programming, in order to describe the optimal journey that guaranties to fishes the future survival. From the model, we could reconstruct optimal journeys; find out relations between the migration process and individual weights. We divide the stream in three sectors, characterized through substrate and cover types. Sector I (superior) has higher cover proportion, low deep; erode bank, logs, roots, floating leaves, and thick substrate. Sector II (middle) has an intermediate cover proportion: erode bank, submerged and marginal vegetation, few logs and branches, with thin substrate. Sector III (near to the estuary) has low cover proportion, very diverse, heterogeneous substrate, runners and deep sites. The model shows that sector I is chosen especially by low weights and early ages individuals, with gradual displacements to the sector II, mostly occupied by mean weight and age fishes. Sector III presents high permanency of major weight and age fishes. This fact could respond to their better adaptation capacity to profundity and runners. The model considers simultaneously weight, age, competence, individual behavior and environmental characteristics related with food and protection supply. The dynamic programming has been a suitable structure for this problem that incorporates observed data and stochastic processes.

Keywords : Optimization; Juvenile salmonids migration; Patagonia.

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