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Protestors gathered outside Dover's Eastern Docks on Thursday morning when the trade in exporting live animals resumed at the port.
And they are expected to be there every week while the shipments continue.
A Dutch company submitted a request to operate from the port after the Port of Ramsgate tried to stop the trade last September.
Dover Harbour Board announced that following two berthing trials and some modifications to the ship, the MV Joline, permission had been given to start a ferry service from the port's car ferry berths "within specified weather limitations".
The harbour board said Barco de Vapor had indicated its principal business would be the carriage of livestock transporters, which is a legal trade.
"The High Court has previously made it clear that Dover Harbour Board must facilitate all legal trades through its port," the board said in a statement.
"The Department for Environment Food and Rural Affairs (DEFRA) is responsible for arranging the conduct of all necessary animal welfare checks by its regulatory agency, the Animal Health and Veterinary Laboratories Agency (AHVLA), throughout the duration of the service in order to ensure that all of its requirements are met.
"We respect the positions of all concerned about this particular trade and hopes that the significantly shorter sea-crossing from Dover, when compared with other ports, will at least bring some relative benefit for the welfare of the animals in the transporters."
Animal rights campaigners gathered at the port when the first shipment, believed to involve around 500 sheep left, bound for Calais.
It is expected that there will be one sailing a week.
Full story and reaction in this week's Dover Mercury.