In Three Men in a Boat by Jerome, what is the meaning of the subtitle, "A Fishy Tale"?

Some editions of Three Men in a Boat include summary prompts at the beginning of each chapter. One of these tags at the start of Chapter XVII is “A fishy story.” Here J. describes the encounters he and George experience at a local inn in Wallingford. A large trout was mounted in a glass case. Every fisherman that came in had a different story to tell about how he had caught it, how much technique and struggle were involved in the catch, and how much it had weighed. J. and George were amazed at the stories. But when George finally climbed up to get a closer look at the fish, the case fell, and the fish broke into hundreds of pieces. It had been made of plaster of Paris. The narrator played on the dual meanings of the word “fishy.” Yes, the story was about a fish. But it was also odd, suspect, and questionable as far as the truth was concerned. Fishermen are known to exaggerate.