Juvenile sunfish- need help with this little guy

Hello, 

the first pic is an example of a juvy bluegill that came from lake mendota in wisconsin, that is for comparison.

the second pic is the fish in question, this one was caught today out of a spring fed brook that is a tributary to the lower wisconsin river. 

to my untrained eye, these two seem like different species. however, the lower wisconsin has fooled me before with color variations in species. for example, the longnose gar from lake mendota are olive color with spots along the body and yellow fins with spots. but the gar in the river are totally silver with pale spotted fins. (fun fact)

so anyways, anyone have any ideas here?

I think I am a Bluegill expert. They do change color a lot and very quickly. That one does not look right. Bar number and solid appearance odd for Northern Bluegill. Body elongate. My approach would be to grow fish out, if legal. 

Although very tempting to take it home to my tank, it is illegal in WI to take live fish from a waterway.

Although very tempting to take it home to my tank, it is illegal in WI to take live fish from a waterway.

hence if legal

Is it my imagination or is the little flap on the operculum dark in front and light in back on the fish in question?