The swans were originally given to Lakeland in the 1950s after a resident living in England wrote to Queen Elizabeth asking if she would donate a pair to the city.
The swans which had been living in the city previously had all been eaten by alligators or dogs.
The Queen responded by sending two royal swans from her flock to the city, which arrived on February 7 1957.
However, the pair bread and now more than 86 live in Lakeland.
The city, which has a swan as its symbol, decided to reduce the flock to 50 so they are still able to care for the birds.
Swans were auctioned off in pairs for 400 dollars (£310) each.
A city spokesman told the PA news agency: “We needed to get the population in check for the size of the lake they are on. We also have a large number of ducks, geese and other waterfowl that call Lake Morton home.”
Because of the popularity of the swans, they held a lottery to decide who would get to purchase a pair. There were 80 registrants, with 18 successful buyers chosen.
The money raised will go back into the city’s swan fund, to help care for the birds.
