The decision, which came into effect last Sunday sees all restaurants, coffee cabins, bars and shops on board ferries closed until further notice.
It is the second time during the pandemic and food and drink and other services have been halted.
Positive Covid tests have disrupted a number of CalMac services throughout the week, including on the Stornoway to Ullapool route, Wemyss Bay and Rothesay, Oban to Coll and Tiree, as well as the Oban to Craignure service.
The spike of several positive Covid cases across the CalMac network has left the carrier with a reduced crew.
A CalMac spokesman said: ‘We understand the effect this will have on our customers; however, we have taken this decision to allow us to focus our resources on maintaining the service, while prioritising the robust cleaning protocols we have in place, and limiting contact between customers and crew.
‘We are communicating with our customers to urge them to come prepared for their journey, particularly longer sailings.’
Meanwhile, some travellers hoping to spend Christmas on Arran were left disappointed, claiming that Christmas had been ruined, after all sailings to and from Arran were cancelled on Christmas Eve after the 1.55pm sailing from Brodick, owing to weather and sea swell conditions.
Positive Covid tests, staff shortages and staff isolating were also blamed for cuts to ScotRail's services, which will take place throughout January.
The rail service announced the cuts at the start of the week in order to provide their customers with a level of certainty about which services are running in the coming weeks.
ScotRail said that it was better for some services to be temporarily withdrawn on a planned basis than to have chaotic last-minute cancellations.
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