db wrote on May 5^th, 2011 at 6:10am:

The more they taste like fish, the more they decomposed between filleting and cooking.

I would say the amount of decomposition between dying and filleting is a bigger factor in taste.  

I've had much better luck with filleting fish before they die and then hauling their fillets around for a few hours than I have had with hauling dead fish around for a few hours and then filleting.  A ziploc of fillets in a wet canvas bag and kept out of the sun works quite nicely when travelling.  At camp I'll take that same setup, put a small rock in the canvas bag, tie a rope around it, and throw it out into the deepest water I can find around camp.  Never had a problem with "fishy" tasting fillets doing things this way.

As soon as I've caught enough for dinner, the fillet knife comes out, whether or not I'm done fishing.  About the only time I violate this rule anymore is if I'm staying relatively stationary in cool water while I fish and the walleyes on the stringer are plenty lively.  As soon as I'm ready to move, though, the jig is up for my catch.