PORTLAND, Maine — The board that oversees the local harbor approved a change to the fees charged to steer large, foreign ships in and out of Maine’s busiest port on Thursday night, after passing a similar rate hike in the spring.

The Portland Board of Harbor Commissioners voted unanimously to set the minimum fee that pilots charge to ferry ships through the harbor to the equivalent of $1077, altering a May decision that had hiked the fee even higher above the longtime minimum of $709.

The May increase is the subject of the legal challenge by the operator of the struggling Portland-Nova Scotia ferry, which has claimed in legal filings that the harbor commission abdicated its regulatory duty by not scrutinizing the finances of the two men who handle all piloting in Portland. And Bay Ferries Ltd.’s attorney said the company will challenge the latest decision as well.

“We’re obviously going to seek judicial review,” said lawyer Harold Pachios, a founding partner with Preti Flaherty, noting that the board did not require the pilots to testify or disclose their income.

The new pilot fee is smaller than the $1,200 minimum that the pilots requested and the board approved in May, but it still represents hundreds of thousands of dollars that Bay Ferries and other companies that frequent Portland harbor will have to pay annually. The new fee will likely come into effect in 2018.

State and federal law requires that a pilot guide large, foreign ships in and out of port.

Following the vote, board chairman Thomas Dobbins rebuffed Pachios’ claim that they are not doing their due diligence, suggesting that it was little more than lawyerly bluster. He noted that Bay Ferries alone was protesting the change and that the committee had not heard complaints from Eimskip, the Icelandic shipping giant that brings dozens of ships into Portland each year.

“This fee also affects all the tugs and barges [that engage in foreign trade] but you don’t see them in here jumping up and down,” Dobbins said.

During brief deliberations Thursday, Dobbins and other commissioners said that they felt the fee increase is reasonable because the pilots have lost business and revenue in recent years as the number of tankers calling at the Portland-Montreal pipeline has plummeted.

“We used to have two ships sitting at the pipeline all the time and they were the big payers — the goose egg as it were,” said board member Dan Haley.

In nearby ports, pilotage fees range from $2,370 in Searsport to $750 in Portsmouth, according to documents the Portland pilots sent to the harbor commission.

The new minimum fee was set at 150 pilot units, which are a measure of ship size and currently priced at $7.18 each. Beyond that minimum, pilots charge based on the size of the ship and amount of fuel used.

A lawyer for Portland’s two active pilots said his clients are not yet sure what to make of the new fee, which is lower than what they’d asked for but still much higher than the previous minimum.

“It was totally out of the blue,” Twain Braden, an attorney with Thompson Bowie & Hatch LLC, said of the decision.

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