The NRCTP has put out an overview of its study, a five year program to track the migration patterns of cod in the waters of the Northeast, including the waters of the Gulf of Maine. Click on the pic above to get to the program web page.
In looking at the results, I find figure 7 to be the most illuminating. It depicts the least concentration of migratory fish in an area extending from Penobscot Bay out to Georges Bank, almost as if the greatest concentration of migrants can be found following a path that skirts the outer boundary of the Gulf of Maine.
You can download the report and the figure mentioned above from the page located here.