Ken H. Andersen, Aqua, Technical University of Denmark Title: Modeling of ecosystems Time: Fri Jun 19, 2009, 2pm Place: Building 28, Room 2.123, Campus Golm, Universitaet Potsdam Abstract: "Master, I marvel how the fishes live in the sea". "Why, as men do a-land; the great ones eat up the little ones". So wrote Shakespeare more than 400 years ago in his comedy "Pericles". Even though the principle of big fish eating smaller fish is obvious, it has been largely underexploited by fisheries biologists. I will formulate a simple model of a marine ecosystem based around the simple "big fish eat smaller fish" rule. The model is in the form of coupled partial integro-differential equations, but even then analytical solutions are possible. I will also show results of numerical integration of the model, which demonstrate how the system as a whole reacts to a modern large-scale industrial fishery.