Not only is Potholes no longer very productive for spiney rays, Moses lake and Banks lake have gone through a similar decline. In Moses lake they thought the Carp wallowing in the shallows during spawning of the spineys might be a factor. But a Carp exclusion net did not do much to bring them back.
The Walleye has definately contributed, but that doesen't explain it all.

Think of the word Panfish!! The take (of croppies especially) on these lakes in the heydays definately contributed. Lotta spawner size ended up in frypans.
In Banks Lake, they put out some artificial reefs here and there for croppie spawning and cover,but it hasn't seemed to do much so far.
Seems to me like once a species gets badly depleted, it's a long,hard road to bring it back unless ALL the factors leading to decline are removed at once
Probably ain'ta gonna happen.