In 1915 a factory was established by the company for boiling mussels. About 40.000 cans of 1,5 kg. each was produced per year and live mussels were sold out of the oyster basins. Later on additional locations for boiling mussels were established, in Nørrebro in Nykøbing among others.
In 1918 the Oyster Company could produce up to 10.000 cans a day, but sales dropped drastically to a mere 700 a day, at the end of 1st World War.
The mussel fishery did not achieve as great a scale as first anticipated. In the years between 1918 and 1940 only between 240 and 2570 tons were caught. Later on the tides turned and in the years during the 2nd World War up to 80 tons were landed in Nykøbing.