Two Brazilian export companies were found to be in possession of a record 28.7 tonnes of shark fins that had been caught illegally.
Ibama, Brazil's environmental protection agency, calculated that a catch of that size required the deaths of about 11,000 blue sharks and shortfin mako sharks.
The fins were going to Asia, where shark fin soup is a popular dish.
The names of the two businesses are not known.
Nearly all of the shark fins, or 27.6 tonnes out of a total of 28.7 tonnes, were seized from a single export business in Santa Catarina state, in southern Brazil.
At the international airport in So Paulo, Ibama seized the final 1.1 tons.
The organization claimed that it may have been the largest weight-wise seizure of shark fins from illegally fished sources ever made.
Shark fishing is prohibited in Brazil. Ibama claimed that the businesses used licenses for other species of fishing before illegally pursuing sharks.
Additionally, the agency claimed that during their shark fishing expeditions, the companies killed thousands of seabirds.
The two businesses have each been fined.
Ibama issued a warning that the population of sharks has decreased due to illegal fishing. Just three weeks ago, the shortfin make shark was added to Brazil's list of endangered species.
