As part of my research on traffic patterns in northern Manitoba for my layout, there are obvious sources (mines, concentrators and smelters, pulp mills, sawmills, grain, fuel, propane) and less obvious sources like fish. 

Significant ice and mechanical reefer traffic taking produce, meat and groceries to northern communities was an important source of northbound traffic into the 1980's before the roads were sufficient to handle truck traffic.  But what sort of stuff went south in what would otherwise have been empty cars?  I stumbled across a document from the Manitoba Government ( http://www.manitoba.ca/waterstewardship/fisheries/commercial/history.pdf ) covering some of the history of the commercial fishery in Manitoba.  While the big lakes (Lake Manitoba, Lake Winnipegosis and Lake Winnipeg) are by far the most important for commercial fishing, there was and is significant commercial fisheries elsewhere in the province.  

The document offers this map:

What is interesting is that I have several new traffic sources in The Pas, Flin Flon, Lynn Lake, Thompson, Snow Lake and other points north.  While this traffic now goes by truck to Winnipeg and points south, I can make a good case for shipment by rail in the 1980's when the highways were still not up to snuff in the region.  Photos from that era show up to 4 mechanical reefers on the head end of the Hudson Bay passenger train, and others show ice reefers and mechanical reefers in many of the trains.  As well there was some of the traffic shipped as TOFC so there are several options to develop further traffic on the layout. 

The CN freight shed in Thompson Manitoba saw a significant number of mechanical reefers through the mid 1980's.  This photo by Mark Perry shows the sort of traffic that can be modelled.    

I guess I need to start writing up car cards for reefer traffic to several additional destinations.