Definition - What does Sustained Yield mean?
A sustained yield is the amount of a certain resource that can be harvested or obtained without causing depletion. Sustained yields are most commonly applied to forestry and fishing activities and limit short-term harvests to allow for longer-term regeneration of resources from the remaining parent material.
Safeopedia explains Sustained Yield
If we removed as many fish from seas, hunted as many deer or felled as many forest trees as we were able to, these resources would soon be depleted. If we wish to harvest a biological resource from nature, we have to obtain a permit. Permits are issued in such a way that the maximum amount of resources that still allow for regeneration of the resource are removed. In practice it can be difficult to determine how much harvesting should be allowed, and there are always those who exploit natural resources illegally.