"It is not possible to predict how much it will eat."
-I agree with this statement.
"But lets say I can know EXACTLY what each fish is going to eat each day because I give each fish a weighed ration in isolation of competitors."
-I'm not sure how you get to this statement from the previous sentence unless you are playing in the purely theoretical realm;
No not so. If an experiment is performed on fish in isolation where only that fish can eat its ration the conversion properties can be determined. Experiments just like this have been performed many times over. To be sure, I know it won't help you in any way. But yes, if consumption is controlled then conversion can be determined. AND the variation for a group of fish is small and the functions resulting from the analysis practical and effective.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
