The fish were at market weight of 3.3kg and were due to be harvested.
Cermaq, owned by Japanese company Mitsubishi, said the escape at its Ensenada Lorca site was caused by damage to a cage net after several days on heavy storms.
The final number of escaped fish has yet to be verified, but it is estimated to be in the range of 40,000 to 50,000 fish, said the company. Recapture procedures have already started.
“Cermaq is working closely with all relevant authorities in handling the situation and will review the exact causes of the escape,” said the producer, which also farms in Norway and Canada.
Chile’s state aquaculture service Sernapesca said inspectors has visited the site and were verifying that measures demanded by regulations, including a contingency plan and the recapture of fish, had been activated.
It is the third escape reported to Sernapesca this year, following minor incidents that affected Blumar and AquaChile in the Aysén region.
At the end of last year, Cermaq reported that about 20,000 coho salmon escaped from its Caucahué farm in the Los Lagos region.