In this RCW the words "fishes for" relates to the "act of fishing," not necessarily fishing for another. There is another part to the violation, though. This law specifically pertains to either fishing without a license, or with a license but overlimit (less than 2x) either bag or possession, closed area, closed time, or prohibited method, etc. It would appear that the prohibited method is where we should look at.
The RCWs seem a bit ambiguous, (sorry for the 4 syllable word

), on the issue of which rod is which. The rules state "no more than one line" but they don't say that you have to clearly label each rod, like a crab pot.
It seems that taking turns on the bank of rods would be okay provided nobody has limited out, there is one rod per person, and everybody has a license. The opinion that I got from three different fish cops is this.
All said that if they "SAW" you set one rod, say back bouncing, but then reeled in another, they would consider you to be using two rods, even though there may be two or more people fishing. Two said they would probably use a great deal of discretion if you were setting your kid's line, but one was a hardnosed SOB and said he would carve a ticket anyway. It comes down to a legal phrase called "misdemeanor presence." That means that a law enforcement officer needs to see you commit the misdemeanor for them to ticket you. If you set all three rods up for your clients, and one for yourself, and then afterwards come around the bend where there is an officer, he didn't see you "fish" all the rods, so he can't ticket you. These are the opinions of three WDFW officers, not mine. You might want to take it to court if you do get tagged. That way the ambiguity (sorry, 5 syllables :)) would be cleared up as a matter of case law. Any takers??
They all said the "hand off" is a no-no and would be ticketed if seen.
Andy