The traditional prerogatives of Brazilian business interest groups included a large measure of control over the harbors and the waterfront districts of their ports. Business interest groups had helped supervise these areas from medieval times with the Spanish consulados to the nineteenth century with the Anglo-Saxon chambers of commerce. Both central and provincial governments recognized their right to advise on and assess all matters relating to the water-front and harbor of their entrepôt. Business interest groups could also offer the expertise of a membership familiar with water-borne trade. As with most other prerogatives, group authority over these areas was customary, not statutory. It was shared with two government agencies, the customs house (alfândega) and the Port Authority (Capitania do Pôrto, later Inspetor do Arsenal). The three did not always agree on the needs of the area, and conflicts were frequent. The general aim of business interest groups — the commercial associations in particular — was to make seaborne commerce in their entrepôts as cheap, efficient, and safe as possible. They were driven by rivalry with competing entrepôts to attract shipping and to procure a competitive edge that would expand their trade areas. Such policies helped determine geographical patterns of development.

Safe and easy access for ships was primary for ports and for their business interest groups. The groups recommended lanes of access and exit and anchorages for shipping, and helped draw up port regulations. They supervised navigational safety, not only for their immediate harbors, but for distant approaches such as the mouths of the Amazon River and Patos Lake(Lagôa dos Patos) in Rio Grande do Sul.