At the end of the 16th century, and the beginning of the 17th century, the instability of the communication between the Ria and the sea led to the closure of the canal, preventing the use of the port and creating unsanitary conditions caused by the stagnation of the lagoon. This led to a great decrease in the number of inhabitants - many of whom emigrated, creating fishing grounds along the Portuguese coast - and, consequently, became the basis of a great economic and social crisis. It was, however, and curiously, in this phase of recession that one of the most remarkable Aveiro temples was built, in full Filipino domination: the Igreja da Misericórdia.
In 1759, D. José I elevated Aveiro to city, a few months after he had condemned for treason, to the scaffold, his last duke, a title created in 1547 by D. João III. For this reason, and at the request of some notable people of the city, the new city was given the name of Nova Bragança instead of Aveiro, by Royal Decree of April 11, 1759. With the fall of the Marquis of Pombal, after D. Maria I became queen in 1777, soon this one ordered to return the city to its previous designation.
The city was made Officer of the Military Order of the Tower and Sword of Valor, Loyalty and Merit on March 29, 1919 and Honorary Member of the Order of Freedom on March 23, 1998. Aveiro was one of the main ports involved in cod fishing during the dictatorial period.