PORTLAND, Maine — Is it a family-friendly marketing tactic that could boost tourism, or a costly mistake that will cause an unsustainable revenue loss for Casco Bay Lines?

Opposing perspectives surround a proposal to increase the eligibility age for CBL children’s fares from 9 to 13. The proposal is expected to be discussed March 25 at a meeting of the CBL Board of Directors’ finance committee, and could be put to a full board vote the next day.

“People can’t understand, on the face of it, why it is needed,” Peaks Island board member Twain Braden said March 9.

Longtime Peaks Island resident Jane Gerard said earlier this month the proposal is unnecessary and expensive.

“I don’t know how we are going to make up for $78,000. It is going to cost all the rest of us in rate hikes,” she said.

The estimated annual revenue loss was calculated in November 2014 by CBL Operations Manager and City Councilor Nick Mavodones Jr., but is an admitted extrapolation because the ferry service does not fully track the ages of passengers.

Increasing the age of eligibility to 13 would reduce revenue from the Portland School Department, Mavodones said, but the larger hit comes during the tourist season.

Data supplied by Portland Public Schools Controller Ray O’Donnell shows the department has spent between $49,000 and $54,000 in the last three years on CBL passes for island students. The vast majority, 53 of 57 this year, are from Peaks. The $14,000 in revenue CBL might lose from city schools is an estimate of the adult fares charged to students ages 10 to 13.

Fiscal year 2014 data showed CBL child fares for regular routes and tours was $79,000. By assuming 80 percent of that amount would become child fares, which are half the adult fares, Mavodones arrived at an estimated revenue reduction of $63,000 annually.

When students do not receive tickets from the city schools, they can receive monthly passes made available by the island council using funds from the city.

Braden complimented the work done by Mavodones, but called it a “worst-case scenario” that does not reflect how reduced fares could increase travel by families.

“It is hard to say, not having done an economic impact study,” Braden said.

Peaks resident Margaret Kelsey said March 14 she has been coming to the island for 42 years, and asked Braden to work on reduced fares because she opposes the current policy.

“Why is the adult fare imposed on a 10-year-old child? Nowhere else in the country is a child considered and charged for things at an adult rate until at least age 13,” she said.

Fares for children from ages 5 to 9 are priced at 50 percent of adult rates. Rates are $2 to or from Peaks Island from mid-October through mid-April, and $3.85 for the rest of the year. Passengers 65 and older also receive a 50 percent discount.

Kelsey also wants ticket booklets for child’s fares, which could discount fares even more.

“You can buy a book of tickets for your dog, your bike, if you are an adult. You may not buy a book of tickets for your children, because it does not exist,” she said.

Charles Burr, also a board member from Peaks, said he is concerned about the fiscal consequences as well. A second phase of work at the ferry terminal off Commercial Street will begin this year and a new car ferry will be needed, he added.

“The idea in itself does not bother me,” he said this month. “Is there a way of recovering this money, and not 10 years down the road? It is the fiscally responsible thing to do.”

Braden said those capital projects will be accomplished.

“The common misconception is ticket sales have a correlation on capital upgrades,” he said while praising CBL General Manager Hank Berg for finding funding sources.

Gerard and Kelsey agree the islands offer a unique, challenging way of living that is dependent on riding the CBL’s six vessels. The nonprofit ferry line was established as a quasi-municipal service in 1981.

“This is an expensive lifestyle out here on the island, it is not an easy lifestyle, we have to come and go, we are completely at the mercy of CBL,” Kelsey said. “Let’s not burden the year-round residents.”

Gerard is now eligible for the senior fare, and said she also worked for three years to get a reduced fare one day a week for the car ferry. She said she brought up a family while paying fares as charged now.

“I think this is overkill, I think we have enough other ways of covering children,” she said. “When our children and our grandchildren come, they pay the prices that are asked of them.”