Passenger numbers on the Gourock to Kilcreggan ferry have fallen by 18%, according to the latest figures reported to Strathclyde Partnership for Transport (SPT).
The four-week periods ending November 1 and November 29 saw steep falls, with cancelled sailings being blamed on difficult weather conditions.
In October there were 3,881 passengers on the Island Princess, owned by Clydelink, compared to 4,741 in 2013/14, 4,369 in 2012/13 and 4,335 in 2011/12.
And a total of 3,868 people used the SPT-subsidised service from November 1-29, compared to 4,725 in 2013/14, 3,637 in 2012/13 and 3.732 i 2011/12.
Ten years ago the figures were far higher – SPT records show that in October and November 2004 the total figures were 5,800 per month.