Richard Boone refers to Harry Carey Jr. (Jonah) as "old man," but Boone's is actually four years older than Cary.
The title is based on the biblical tale of the reluctant prophet swallowed by a whale as told in the book of Jonah.
While the title "Jonah and the Trout" refers to the biblical tale of Jonah and the whale, this episode could as easily be titled "Ahab and the Trout" since the fisherman's obsession with catching the trout has ruined his marriage, work, and his life.
Paladin's last observation about Jonah's obsession comes from Charles Lamb's letter to Samuel Coleridge: "Man, in the pride of speculation, forgetting his nature, and hailing in himself the future God, must make the angels laugh." .