I find apple too sweet but alder hits the spot, especially if it is alder from the PNW trees rather than the stuff available at Lowes which has a very muted flavor and comes from who knows where. Alder goes well with any meat, but the same can't be said for some of the other woods (ie. mesquite and hickory)
On my pinks this year i use three parts alder...one part mesquite....i cut the skinless strips thin, they soak up the brine good. brine is 50/50 salt, sea salt, white sugar, brown sugar, bbq sauce. i pepper before i place on the rack. 3 hrs does it for me in my little chief with these summer temps. after one hour of smoking, i pour out the burnt chips, and replace the empty pan. the burnt/cooking chips is what gives the fish a bitter taste. often i will add a second partial/small pan of chips, at hour two, and then remove after 30 minutes and pour out.