Winter high-speed ferry service between New Bedford and the Vineyard is expected to be sharply reduced, and may be abandoned altogether unless passenger numbers increase.

In the face of rapidly falling ridership, the ferry’s operators intend to cancel all weekend runs and reduce weekday trips by a third. The changes are expected to be formally approved by Steamship Authority governors at their monthly meeting in New Bedford on Tuesday.

In a letter to the SSA, the operators of the service, New England Fast Ferry, say declining patronage and skyrocketing fuel prices have made the route economically unfeasible between mid-October and mid-April.

During the 182-day period from Oct. 16, 2006 to April 15 this year, the New Bedford fast ferry carried fewer than 14,000 passengers, for an average of just 12 passengers per trip. This was not enough to cover fuel and crew costs.

“The operators are proposing to cut the service down to just Monday through Friday, with no service Saturday and Sunday, and to operate two round trips a day, in the morning and late afternoon,” said SSA general manger Wayne Lamson yesterday.

“They are also saying that if the low ridership numbers continue, then next year they propose to cut out the service altogether.

“They would stop operating around mid-October until at least mid-April.”

The high speed ferry operation was licensed by the SSA in 2003 on the basis that it would provide year-round service. The agreement requires New England Fast Ferry to operate a minimum of two round trips a day, seven days a week through the off-season.

Mr. Lamson said he accepted that the operators had “tried really hard for three seasons to make it work but there just doesn’t seem to be enough demand. An average of 12 or 12.5 passengers per trip is just not cutting it. It doesn’t even pay the cost of fuel and crew.

“Their ridership numbers are down about 25 or 26 per cent from the year before.

“They have put us on notice that next year there might not be any service, but they felt they should give people some advance notice before potentially pulling out altogether in the fall of 2008.”

But boat line governors will not be required to consider that possibility yet, Mr. Lamson said.

“What the members are looking at next week would be an amendment just to cover this off-season. They won’t be addressing the longer-term issue until after this off-season is over,” he said.

He said management will recommend to the governors that they agree to the amendment.

SSA governors voted 4-0 with one abstention in August 2006 to approve the high-speed ferry service. The contract was for seven years, until September of 2011.

At that time, it was projected that the private operator would carry 130,000 passengers, a year and pay about $315,000 in fees.

The late Nantucket governor and board chairman Grace Grossman abstained, criticizing the agreement for financial and policy reasons.

The late Fred C. Raskin, who was chief executive officer of the SSA at the time, also found the projections exceedingly optimistic.

“I have seen few financial analyses that have more assumptions built into them than this one,” he said.

Tuesday’s meeting also is due to consider the renewal of the boat line’s catering service. Boston Culinary Group — the current operators — tendered the lone bid.

Governors also will consider a complicated proposal to make greater use of the lift decks on the new Island Home, on a trial basis, and will discuss guidelines for advertising on boats and in SSA terminals.

The meeting will be held in room 314 on the third floor of the New Bedford City hall, 133 William street, starting at 9:30 a.m.