The protesters came together at around 7:00 pm, and gathered around the main entrance to Campo Pequeno.
In addition to whistling and booing anyone who entered Campo Pequeno, the protesters made noise using horns, vuvuzelas and drums.
Yesterday evening, a bullfight in homage to the bull-fighting rider João Moura was taking place in Campo Pequeno, which also included the participation of his son, João Moura Jr.
In February of last year, João Moura was arrested following the execution of a warrant to search his property, in Monforte, which resulted in the apprehension of 18 malnourished dogs.
Protesters displayed banners and posters that read messages such as "Down with animal torture"; "It's a national shame"; "My tribute goes to the greyhounds that survived João Moura" and "Bullfighting is not culture, it is torture".
An IRA, Intervention and Animal Rescue, bus was also parked next to the protest. A banner was placed on the bus with images of the dogs when they were found and the message: "João Moura, we brought your dogs for the tribute".
A spokeswoman for the People-Animals-Nature (PAN) party, Inês Sousa Real, was present at the demonstration and, speaking to journalists, said that "it is absolutely revolting that the bullfighting sector has paid this tribute".
"To honour someone who already makes a living sacrificing animals in the arena is absolutely incomprehensible, but even more incomprehensible when it comes to someone who has a criminal case against him for mistreatment of animals, namely 18 greyhounds that they were left to starve," she stressed.
Pointing out that "there are no untouchable citizens" and that "the bullfighting cannot continue to be above the law itself", Inês Sousa Real stated that "bullfighting has its days numbered".