It looks like he's eating something off the surface of the water to me. Small bugs maybe?

When you say your water parameters are "fine"...what exactly are the numbers? Your water looks like it has a high amount of DOCs and not much oxygenation. Normally when a fish is breaching like that, there is a gill issue (or less often, swim bladder). First thing to look at is water quality. Second is parasites, such as gill flukes....or BGD (bacterial gill disease). If it was a once or twice thing...it could be the fish just trying to clear its gills from some debris but several days points to issues for sure. Any chance this is one of the bigger fish in your pond? If so, it may be insufficient oxygenation. As the temps go up, the oxygen content goes down in the pond.

Yes, that is the largest fish in the pond. How do I increase oxygen? I have a waterfall and a small spitter running 24/7. I had suspected that it was low oxygen. Thank you so much for your response. What do you mean by DOC's?

Dissolved organic compounds. It looks like perhaps you don't do - or need to do - water changes. Do you test your water? What are your numbers for:

Ammonia

Nitrite

Nitrate

pH

KH

I would recommend getting an air pump and airstone/diffuser to increase oxygen in the pond.

Your fish appears to be piping. IOW, surfacing to take in air. He needs more oxygen in his "house". Follow ademink's advice and get him an aerator, the sooner the better. Fish need dissolved oxygen in order to survive.