>Is it possible to get 10 grams without supplementation?  How >much fish
would a person have to eat to get 10 grams?

very roughly..
if red salmon is about 10% fat/oil, and the oil content is about 20% Om-3,
that would be 500grams of salmon.
however in true paleo diets sea mammals and fish roe, eels wouls also be
eaten, and the salmon woul dhave all its fat available, whereas canned or
filleted the fatty belly flap is removed.

andrew