The harvesting effect on a fish population

Fishery is one of the main environmental factors affecting fish population. In this paper we study the dynamics of population’s dimensional distribution under the influence of environmental variations with and without a fishery impact. The characteristics of population under consideration correspond to pelagic or semi-pelagic population, such as the populations of pollack (Theragra chalcogramma) inhabiting the northern seas of Pacific Ocean. To study the effect of fishery upon a population the problem of harvesting optimization with the amount of profit for a given time period as a criterion function is solved. The impact of population replenishment on the population and catch dynamics was studied and the smoothing influence of dimensional structure on the changes of environment and fishery was revealed. The seasonal changes of environment only increase the population stability.