While studying aquatic systems there will also be considered population dynamics. A population is the whole of common organisms who are spatially and temporally separated and which engage in a genetic exchange. Using the example of a shrimps population off the coast of Tanzania the dynamics of this population will be modeled especially with a matrix model. In a so called stage structured population model the temporally and spatially development and the reactions to changed conditions in the environment will be examined, for example rainfall, temperature, salinity and other with a matrix model under consideration of the spawning behavior and the changes, corresponding to the stages, between the different habitats. In a first step the model should reproduce the so far collected data and in a second step it should allow advanced statements about the behavior resp. the development of the populations.