Woods that are good to use for smoking fish are:
Apple (or any other fruit wood, peach or pear)
pecan (or other nut wood but that is most common around here)

What we are discussing here is a hot smoke, that will cook the fish, just like when we say 'smoked' meat on the grill. Hot smoked meats are NOT preserved.

True cold preservation smoking needs cooler temps and does preserve the meat, but does not cook it.