I gotta disagree with that one. A fish 4 foot deep is going to be in the field of view for approx 1.3 ft. That is with a standard 20 degree transducer. There is no way it could measure 10 ft away even at the edge of the cone. Now with some of these new fangled super wide, multi-transducer setups, I could see where that might apply. I definately go along with the fast trolling this time of the year. I've been doing that for years and it does work.
Fair Winds and Following Seas
Bill H. PTC USN Ret
Chesapeake, Va