CONSTANT EFFORT AND CONSTANT QUOTAFISHING POLICIES WITH CUT-OFFS IN A RANDOM ENVIRONMENT

摘要: . Consider a population subjected to constant effort or quota fishing with generaldensity-dependence growth function (because that is poorly known). environmental random fluctuations either affect an intrinsic parameter birth/death rates, thus resulting in two stochastic differential equations models. From previous results of ours, we obtain conditions for non-extinction and existence size stationary density. Constant (which always leads extinction environments) policies are studied; they hard implement extreme sizes. Introducing cut-offs circumvents these drawbacks. In deterministic environment, wide range values, cutting-off does not the steady-state yield. This so environment will give expressions showing how average yield distribution vary as functions cut-off choices. We illustrate general plots particular case logistic growth.