Two Ethnics

Two ethnics, John and Jack, were sitting in a bar one day, when two fishermen walked in with 2 huge trout, one of the ethnics asked where the guys got the fish, and the fishermen told the that they go down to the bridge, one guy would hold the other by the ankles until a fish was caught.
The ethnics figured that they could to that.
After holding for about 15 minutes, Jack asked John if he had anything, and the reply was "no."
About 15 more minutes passes, so Jack asked again, and again the reply was "no".
Finally, John yelled :
- Pull me up !!! Pull me up !!!
Jack exclaimed :
- Ya got one ?
John said :
- No! a train is coming !