I fear there is but one way to catch a superintelligent fish, and that would be by not catching him. (Sounds Zen-like? Not really...) Just let him come to you, and keep your mind-shields firmly in place. A superintelligent fish, it can be rationalized, might also have some idea of what you may be trying to do--thus also making him a psychic fish.

Yet even by intrigue alone, Mac Carell is a catcher of men

Super intelligence is often accompanied by an over abundance of ego. If this is the case with Mac Carell, perhaps this could be used as a lure?

*begins hatching several plans*
- giving the impression the world has forgotten his claim to fame?
- spreading the word of a greater and more affable intelligence?

.. any suggestions?

And thus, there came to pass the day when the ocean ran far too shallow and against the normal currents for Mac Carell, causing the superintelligent fish to take no other option but to force his nodes into small yet strong webbed feet and take his first wobbly steps upon the land and experience the physical life, just as the coelocanth had done many years prior. (...She was always ahead of him, for she was a bright fish of the tropics!!)

*Darwin sits with a big smile on his face*