All those costal rivers in the south must have supported huge runs of pacific salmon: sockeye, pink, chinook, coho, and chum. Were there were that many fish in a ready food supply there were also villages or even city sized towns dedicated to the harvest. They likely traded as far south as what is today the sea of japan. All or most of them drowned when the ice suddenly melted.
It is worth downloading the .pdf of the map, and any one who can open a .lyr doc for the hydrology.
The lower the altitude (or latitude), the warmer the temperature, so, compared with the iced over parts of the Earth, food would have been plentiful. Also, there's no evidence for the oceans having frozen over (at least, not for long) and there is evidence of some form of navigation going back 100s of 1000s of years, so, yeah, probably lots of trade, and traces of drowned towns are probably down there.