2 food from city center, 1 food from each coast tile = 4 food.
2 citizens' food consumption = 4 food.
But city center is not food from fishes. That's source from the land tile.
In all Civ titles, those +2 foods in center represented slow growth model, while having tiles with +2 food represented minimal food needed to support population that produces it. So any city with just +2 food tiles would self sustain itself, regardless of population level itself, but grow slowly, since methods of food production are primitive enough to not allow any surplus.
Thus any food tile with +2 food is supposed to be self sustaining, while those with +1 food are supposed to be supplementary food sources.
Anyway, +1 food from ocean tiles does not correctly represent the role of fishery in historical sense, as major food source.
And Fish resource is not supposed to represent only places in ocean that have fish, but those with abundant fish, enough to make significant surplus (and not just self sustain the population).
So anyway, if Civ is supposed to represent historical importance of finishing it would start with 1 food, until you get Net or Fish Boat technology that would upgrade to 2. Then have some modern technology that would up it to 3 or even 4.