Yes, Agassiz does recommend authors to eat fish,
because the phosphorous in it makes brains.
So far you are correct.
But I cannot help you to a decision about the amount you need to eat — at least, not with certainty. If the specimen composition you send is about your fair usual average, I should judge that perhaps a couple of whales would be all you would want for the present. Not the largest kind, but simply good middling-sized whales.