• 1 Department of Electrical Engineering

Our aim is to apply some tools of control to fishing population systems. In this paper we construct a non linear observer for the continuous stage structured model of an exploited fish population, using the fishing effort as a control term, the age classes as a states and the quantity of captured fish as a measured output. Under some biological satisfied assumptions we formulate the observer corresponding to this system and show its exponential convergence. With the Lie derivative transformation, we show that the model can be transformed to a canonical observable form; then we give the explicit gain of the estimation.