This gem is a mixture of “a fine kettle of fish” and “a can of worms”, both meaning to describe a difficult situation or problem. My guess is that the speaker was also confusing worms with fish, as worms are bait for fish. Similar malaphors at this site are “I’ve opened up a can of beans” (7/31/13 compliments of Denita) and “that’s a real ball of worms” (12/18/12, submitted by Paula Fow). Thanks to Barry Eigen who sent this one in, and added that if the speaker had only said “a fine kettle of worms”, the malaphor would have been perfect. Perfection is elusive.