What does it do when not sleeping upside down at the surface? Does it otherwise act like you would expect a catfish to behave?

How did you capture it? Could it have been injured in some way? One year is a long time to behave this way if it’s an injury but, I have seen fish with spine injuries that lived but behaved very abnormally

Maybe it is a swim bladder issue but need better description of its overall behavior

Crayfish are babies, not even 1/2" long.
I only keep them about a year before I swap them out for new babies.
The shovel nose is about 3" long.
About same size as other catfish that stay on bottom under rocks.
He swims fine except when he "sleeps".
Been sleeping most mornings since I caught him in a minnow trap last summer.
Only looks pregnant after I throw in the worms for the turtles.
Current batch of turtles are (5) quarter size snappers.
Have had turtle tanks for over 30 years now and never had issues.
May put in smaller tank and monitor better.

Ok. Sounds like you know what you are doing

Since he otherwise swims normally, my guess is the fish is physically fine but just a quirky fish or it has adapted to an environment it does not feel totally comfortable in for some reason…

If all the other fish are ok, I would probably rule out water quality issues