Lack of terrain improvements???

[SerapisIV]

In one of the new screenshots, there is a mapscreen where two cities, Bipi and Samarra (Top Right corner) are size 9 and 12 cities with no irrigation Also, Samarra appears to be completely surrounded by mines. How can a Civ city grow like this? AI cheating? Or is fishing that strong a food resource? They both have decent sized coastlines and are on grassland, but no irrigation