An Atlantic bluefin tuna weighing about 306 kilos was found in SalMar's Arnes facility in the Namsos municipality, Norway, causing an escape Monday.
The company discovered the huge fish while doing work at the site on Monday.
SalMar decided to harvest all the fish in the cage immediately, despite repairing the holes.
More than 100,000 farmed salmon were in the cage at the time of the incident, each weighing around 4.3 kilograms.
The harvested fish was sent to SalMar's processing facility Innovamar in Froya. The tuna, which was killed, will be sold by Akervik in Namsos.
SalMar notified the Norwegian Directorate of Fisheries and the recapture of salmon has already begun.
The company still has no estimates on how many fish escaped the facility.