A restaurant owner from Bayville testified in Manhattan at the federal court insider trading trial of Long Islander Sean Stewart on Thursday that he traded on tips from Stewart’s father and was told they came from his investment banker son.

Mark Boccia, testifying with a grant of immunity from criminal prosecution, said Robert Stewart twice told him there were “short term” opportunities and urged Boccia to invest in his brokerage account for both himself and Stewart.

When Boccia, owner of Austin’s Ale House in Kew Gardens, became concerned about an anticipated merger of two businesses that was supposed to lift the second investment, he testified, Stewart said his son worked on Wall Street and “told me his son knew they were going to merge.”

Sean Stewart, 35, of New York City, formerly an investment banker at JP Morgan Chase and Perella Weinberg Partners, is accused of feeding tips on five deals to his father Robert, 61, of North Merrick, where Sean grew up. Prosecutors say the father and a partner, cooperating witness Richard Cunniffe, made $1 million.

Sean Stewart’s defense lawyers argue that he mentioned business in family conversations but had no idea his father was using it for trades. Robert Stewart has pleaded guilty, but did not clearly implicate his son or agree to cooperate, and is not expected to testify.

Boccia, whose role as a middleman on early trades was not known until Thursday, said Robert Stewart was doing accounting work for a real estate development firm Boccia was involved with in 2011.

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He said he made $7,000 to $8,000 on the first tip from Robert Stewart and shared some of the profit, but lost “$10,000 to $12,000” on the second tip and never got paid back for the money he fronted for Stewart.

The defense doesn’t contest that Sean Stewart’s father was trading on tips, and on cross-examination Boccia conceded that on the key issue in the trial — whether Sean Stewart knew that the trading was going on — Robert never confided in him.

“No, he did not,” Boccia testified.

The trial began Wednesday.