The pond likely has issues with low dissolved oxygen in summer/winter leading to a fish kill, which would explain the lack of fish in the pond.
As far as fish from the river--stocking "minnows" from the river could likely lead to the introduction of unwanted species. Carp, bullheads, white perch, yellow bass etc.
Best to throw a cast net to make sure there is nothing left in the pond, then stock out forage minnows from a bait shop/fish dealer a few months prior to the introduction of sportfish.
