The outer face of the west pier at Scalloway can no longer be used because of damage.
A meeting of the harbour board heard on Wednesday that the crew of the Filla had noticed a large crack between the pier and the shore when they had berthed there in March. It is now deemed unsafe for vessels of any size to use the outer face, although aquaculture vessels could use the inner face.
Port engineer Andrew Inkster said that the cost of repair would be prohibitive, and replacement of the pier, which is around 50-60 years old, was the only option.
Councillor Iris Hawkins said that as a new pier was in the capital programme there was no point in throwing any more money at the existing one.