Presentation and first applications of a dynamic population model for brown trout, Salmo trutta L.: aid to river management

Abstract

A mathematical model representing the long‐term change in a trout population under different river management scenarios is presented. It describes the structure of a population broken down into age classes based on the Leslie matrix; if the population structure for any given month is known, the model should be able to estimate that of the following month. The passage from one month to the next takes into account various relevant factors: survival rate of individuals in the different age classes; fertility rate of females; linear and weighted growth rates; displacement linked to habitat fluctuations using weighted usable area (WUA) values. The model was applied to two French rivers. Regular monitoring of trout populations on the River Kernec enabled comparison of the response of the model with no displacement, with actual variations in fish stocks on the first river. In addition, the knowledge of WUA chronologies on the River Echez made it possible to carry out initial simulations of the response of a fish population to different river management scenarios at the second site.