### 4.3.1 Revised assumptions

In the section 4.2 it was assumed that the number of fishes in the fish population depends on the birth-rate and death-rate of fishes, only. Actually the population size depends on many other obstacles, including harvesting (which is very important in the case of high quality fishes), existing predators, conditions of the enviroment etc.

One aspect of the model that we have neglected so far is the catching or harvesting of the fish. This assumption will be taken into account in the current section.