They tend not to give any form of experience, after all, ya don't learn anything from polishing something.
400 exp.
35
920 each
75 exp each.
usually each trout gives you 50xp
Cooking a tuna give 100 exp. It also heals 100 life points.
You get 50 mining experience for every coal you mine.
50 Fishing XP 77 Cooking XP
Eating a bass would heal 130 LifePoints.
A tree gives 25 woodcutting experience if you cut it down.
All items fluctuate in price. No one can give a definite answer.
They heal 4 HP. Source: http://runescape.wikia.com/wiki/Sardine