Dead Pools

I have a friend who has a natural small pond on his property.
It sits at a low point where a swampy / boggy area drains into, and there is no visible outlet so it probably drains via seepage.
The pond is about 1,000 ft from the nearest running water. It's 15 ft deep in the middle and about 30 ft across.

I was asking him about stocking this pond with fish, but he said that they die due to a lack of oxygen in the wintertime when the pond is frozen over.

So my question to the group is how would you go about making this pond capable of supporting fish?

This is in a zone 3 climate. I considered something like a solar air pump but the average daytime temp during Jan and Feb is around -15C (5F) and pumping air that cold through the water for 8 weeks is likely to freeze the pond solid. So heating the air somehow would be necessary.

In the summer there seems to be enough water flowing through the system, but in winter the ground is frozen so nothing flows in or out.

Thoughts? Experiences?

A solar pump would work well for the warm months. I think some large mass rocks would work well for the winter. I seem to remember in a Sepp Holzer video him talking about the freezing ponds and how when the warmth of the sun hit the ice and stone it would create a sucking action drawing oxygen down into the water. Maybe experiment with some large rocks in the shallower areas that above and below surface.

Hopefully I'm not the only one who initially thought you meant this

It seems to large to cover with a dome, but what if it had solar water heater?
It could be on land or it could be built as a raft.
One end of the piping would be at the bottom of the pond, the other at or above the surface.

Or it could be more of a space heater, glazing over black mesh, heating air and pushing it into the water.
A floating dome greenhouse, with a solar fountain inside.

A solar powered bubbler might be better than a fountain.

Some fish might survive better than others, invertebrates might survive better still.

Wind power,  especially if used directly to compress air might work.
How about an anchored buoy, designed to  agitate the water when the wind blows a tall bouncy mast.

It sounds rich in nutrients. It needs plants that create oxygen. It needs helifytes like iris that send oxygen into the mud through their roots and create an environment for oxygenloving microbes that break down debris that release nutrients the helophytes can use. Bubbling is the way to go. In the way Butler does his natural ponds preferably, see you tube.
In winter drill holes in ice and oxygen can go in do not bang with an axe, the shock might kill the fish. Dump a tree in there and rocks at the south side that help to trap heat. Fish survive in many lakes. Some plants even create oxygen under ice. I got a small pond it froze over all fish survived, i don’t feed and don’t bubble.