Because your pond drains into a stream you will need to contact the MNR about stocking your pond.
When I lived in Grand Valley we had a pond that did not drain into a river, stream etc and could go ahead and stock away.
Depending on the outflow size, distance from stream etc they may say yes or no or you may have to make some changes to go ahead.
They may even limit the type of fish you can stock.
Gice the MNR a call and they will be able to help you out.