Canceled sailings at Washington State Ferries could worsen for Labor Day weekend as crew shortages and quarantines continue to rock the schedules, and rumors abound that some workers might skip holiday shifts to protest mandatory vaccinations.

Travelers are advised to prepare for delays, or consider walking aboard, the agency said in a news release late Tuesday.

The ferry system stopped accepting new weekend reservations for the San Juan Islands and Coupeville-Port Townsend routes, as it can’t guarantee a full schedule.

Six routes will run fewer trips than usual from Friday to Monday, especially late nights, the announcement said. Next week the Seattle-Bremerton route will shrink to just one boat so the ferry Kaleetan can undergo dry-dock repairs.

At least 130 sailings have been missed since February, the worst in recent memory, spokesperson Ian Sterling said. Of these, rider alerts last weekend showed 31 cancellations because of crew shortages.

At least five ferry employees were confirmed in August to have the coronavirus on the job, including two engine-room workers in close contact with colleagues, according to staff alerts.

Meanwhile on Aug. 12, a record 91 crew members requested time off, according to a memo by Nicole McIntosh, interim chief of staff.

She thanked team members on the Mukilteo-Clinton and Edmonds-Kingston routes who showed up early or stayed late to keep boats moving.

“Your commitment to our customers, giving up your own time, keeps our important transportation link operational,” she wrote.

America’s largest ferry system has struggled all year with what rider alerts call a “lack of Coast Guard documented crew.”

One problem is the on-call system, where early-career deckhands might drive anywhere along Puget Sound to meet a boat, earning an unsteady income. Mariners are in short supply worldwide, a challenge that also affects neighboring British Columbia Ferries.

Rumors are flying about a potential sickout by employees who object to state vaccination mandates. Three weeks ago, Gov. Jay Inslee issued an executive order that all state employees must be fully vaccinated by Oct. 18 or be prohibited from working.

Some people identifying themselves as ferries staff took the stage at an anti-vaccination rally Saturday in Olympia to protest Inslee’s mandate.

“I can’t take the shot because I’ve got to stand up for my freedom. I’ll leave it at that,” said one man identifying himself as an assistant vessel engineer, in footage recorded by Austin Jenkins of Northwest News Network.

Ferries management has made available forms to request medical and religious exemptions. Those require a doctor’s description of a worker’s health risk, or a worker to attest that religious beliefs cause them to decline all vaccinations.

Ferry workers unions consider the mandate legal, and urge members to report for shifts.

“Please consider that any action that increases the pressure on the Dispatch system puts an unfair burden on your fellow employees to try to fill your duties. It also is detrimental to the traveling public who depend on us,” said a note Tuesday by six maritime unions and ferries management.

Unions are bargaining over the effects, including the short timeline.

“We’re going to lose people, and it’s going to be a strain on the system at Washington State Ferries, and everywhere,” predicted Dan Twohig, regional representative for the International Organization of Masters, Mates & Pilots.

Among many logistical problems, there should be some means negotiated for unvaccinated crew who retire early to keep their earned benefits, he said.

Four workers at the Washington State Department of Transportation are known to have died from COVID-19 complications, said a mid-August notice by Transportation Secretary Roger Millar.

Elizabeth Pence of Orcas Island worries about reaching her night job sanitizing hospital rooms at PeaceHealth Peace Island Medical Center, across the water in Friday Harbor. Two months ago, her Friday sailing was canceled, so she had to reschedule for a Sunday shift, Pence said. Then she heard from a ferry worker about possible skipped shifts.

“I’m insecure and frightened I might not be able to make it home,” Pence said. If not, a nurse offered a trailer for sleeping after this Friday night’s graveyard shift, until trips become available.

This isn’t the first era of crew shortages, as ferry riders know from 2013, when 31 sailings were scrapped in a single September weekend.

The possibility of employees skipping shifts “is certainly news,” said Sen. Christine Rolfes, D-Bainbridge Island. COVID-19 illness and medical leaves were already aggravating the maritime worker shortage, she said.

Senate Transportation Committee Chair Steve Hobbs, D-Lake Stevens, said the transportation budget contains a study to improve ferries hiring and retention. An initial version of the $400,000 report is due Jan. 1, 2022, the budget bill says.

The ferry Wenatchee has remained docked at Eagle Harbor since an engine fire, which erupted April 22 during a post-repair test sailing. Some routes used smaller boats as managers shuffled the fleet. A 144-car diesel-electric hybrid ferry begins construction next year in Seattle.

Unlike big-ticket capital projects, wages and working conditions are set at the bargaining table and paid from biennial budgets, Rolfes said. In recent years lawmakers boosted wages but strove to trim on-call and overtime costs during the Great Recession, she said.

“Ferry legislators are very aware of the need for funding for the ferry system. The legislators from the rest of the state are hesitant about that,” she said.

Rolfes said frustration is widespread in island communities.

“People have significantly lowered their expectations over the last six months regarding ferry system reliability,” she said.

“In our family, we schedule at least one boat earlier than we normally would.”