There are 16 compulsory pilotage areas and many non-compulsory areas throughout the Atlantic Region. The criteria for determining which ports should become compulsory are: degree of difficulty and hazard in the approaches and within the port itself; amount of vessel movement and manoeuverability and the size of those vessels; design of wharves, slips, and actual space available for manoeuvering; nature of cargo carried on board, e.g. oil, gas, explosives, hazardous materials; environmental concern and the preservation of the ecosystem.