Catching the fish

Jim had an awful day fishing on the lake, sitting in the blazing sun all day without catching a single one. On his way home, he stopped at the supermarket and ordered four catfish. He told the fish salesman, "Pick four large ones out and throw them at me, will you?"

"Why do you want me to throw them at you?"

"Because I want to tell my wife that I caught them."

"Okay, but I suggest that you take the orange roughy."

"But why?"

"Because your wife came in earlier today and said that if you came by, I should tell you to take orange roughy. She prefers that for supper tonight."