Three Blondes Fishing

Three blondes are sitting by the side of a river holding fishing poles with the lines in the water. A Game Warden comes up behind them, taps them on the shoulder and says, "Excuse me, ladies, I'd like to see your fishing licenses."
"We don't have any," replied the first blonde.
"Well, if you're going to fish, you need fishing licenses," said the Game Warden.
"But officer," replied the second blonde, "we aren't fishing. We all have magnets at the end of our lines and we're collecting debris off the bottom of the river."
The Game Warden lifted up all the lines and, sure enough, there were horseshoe magnets tied on the end of each line. "Well, I know of no law against it," said the Game Warden. "Take all the debris you want." And with that, he left.
As soon as the Game Warden was out of sight, the three blondes started laughing hysterically. "What a dumb Fish Cop," the second blonde said to the other two. "Doesn't he know that there are steelhead trout in this river?"