The Bluemull ferry service is running to a Saturday timetable because of an issue which has developed with the bow thrusters on the Fivla.
Shetland Islands Council says the vessel has had to be taken out of service until a repair can be carried out.
Council officials say it is imperative to have full vessel manoeuvrability functions to ensure safety, particularly due to the worsening weather.
The upshot is that Bluemull Sound will operate a single vessel service, using the Bigga, and running to a Saturday timetable.
The council has apologised for any inconvenience caused. Passengers are being advised to check the winter and festive timetable on the council’s website.