CalMac's summer sailings have just one vessel from Ardrossan

The 40-year-old MV Isle of Arran, which has been providing cover on the route since January, will continue in service, on the route for which she was built, throughout the summer timetable, which runs from March 29 to October 20.

In addition, MV Alfred will also operate from Troon-Brodick on return from its annual overhaul.

A shuttle bus and passenger facilities will be available to take passengers between Ardrossan and the South Ayrshire port.  

Meanwhile, for a second year, the summer sailings between Ardrossan and Campbeltown are cancelled "due to vessel availability".

The redeployment plan, revealed on Tuesday, March 5, was forced on CalMac after it was discovered that major repairs would be needed to the Ardrossan-Arran route's normal vessel, MV Caledonian Isles.

A CalMac spokesperson said: "The plan should see sufficient capacity for the demand expected, albeit with constraints around peak times. "

But they ferry company does have a backup plan which it says could improve passenger and vehicle capacity - which depends on trials being carried out at various ports across Scotland.

That would see MV Hebrides and MV Alfred serve Arran, and MV Isle of Lewis serve Uig-Tarbert-Lochmaddy (Little Minch). 

MV Isle of Lewis was not previously able to operate on the Little Minch service but CalMac plans to carry out berthing trials at Uig, Tarbert and Lochmaddy after upgrade works were carried out at all three ports.

If the trials prove successful, the use of MV Hebrides on the Ardrossan-Brodick service would result in a significant capacity increase on the route.

The Ardrossan to Brodick crossing has suffered badly in recent months - partly due to the weather but mostly due to the condition of Ardrossan Harbour, which is owned by Peel Ports.

Read more: CalMac's main Arran ferry to be out of action for 16 weeks after overhaul reveals need for major repairs 

Ferry services had to transfer to Troon last month after the Irish berth at Ardrossan was permanently closed. That meant the secondary vessel MV Alfred, could no longer sail fom the harbour.

Repairs also had to be carried out to the main Arran berth at Ardrossan - which meantMV Isle of Arran was also forced to operate from Troon.

MV Caledonian Isles hasn't operated on the Ardrossan-Brodick route since it was taken out of service in early January for its annual overhaul.

Later that month Caledonian MacBrayne said the 31-year-old ship's return to service would be delayed until early March due to the need for additional steelwork repairs.

But it's now understood that more extensive work will be required, costing £5m and lasting for an estimated 16 additional weeks - meaning the ship could be out of service for around seven months.

CalMac said: "The deployment plan option we're using gives the best service possible to the network as a whole.

"We have a limited number of options given the vessels that are available to us.

"In a longer than usual update, we've also shared information on a further option we are still testing - so you have visibility on our decision-making process and the steps we are taking to do our very best to support services and the communities we serve.

"We are exploring one final option which could allow for improved capacity on multiple routes.

"On completion of overhaul, we will carry out berthing trials with MV Isle of Lewis on the Uig-Tarbert/Lochmaddy (Little Minch) route.

"MV Isle of Lewis has previously been unable to operate a full service on this route, but we will carry out trials following recent upgrades to relevant ports on the route.   

"If the trials prove operationally feasible, we will update the summer timetable vessel deployment so that MV Hebrides and MV Alfred serve Arran, and MV Isle of Lewis serves Uig-Tarbert-Lochmaddy (Little Minch). 

"If the outcome of the trials is successful and MV Isle of Lewis and MV Hebrides are deployed as above, there will be a vessel cascade review and we will communicate any service changes."