Miami River manatees have lost their best friend.

Capt. Jim Ratican, a tugboat operator known along the urban waterway as “the mayor of the Miami River,’’ a passionate environmentalist, birdwatcher and sea-cow protector, succumbed to heart failure Tuesday in Homestead, where he lived with his sister and brother-in-law, Trish and Mark Yanes.

Born James Balfour Ratican Jr. on Nov. 5, 1946, in St. Louis, Ratican was 65, and had long suffered from diabetes, his sister said. He’d been a widower since his wife, Mary Robinson Ricks Ratican — another animal-loving “free spirit’’ — died in 2006.

“He was on the river for 35 years,’’ Trish Yanes said. “He knew every bridge tender...He was a great advocate for the manatees. The picture on his phone is a manatee and its baby...His Christmas tree is covered with nautical-themed ornaments. Lots of manatees.’’

For 18 years, until illness forced him to retire in April, Ratican worked for Miami-based P&L Towing. His boss, Capt. Beau Payne, once a colleague on the river, hired Ratican when he formed his own company.

Payne described Ratican as “larger than life,’’ kind hearted and unforgettable in tropical-print shirts and flip-flops. He could pass for the Grateful Dead’s Jerry Garcia, and loved playing Santa Claus for school kids and parties.

“I know the world’s a worse place now that he’s not in it,’’ Payne said.

Most of Ratican’s work involved towing ships up and down a 5.5-mile stretch of the Miami River.

“Mainly, he drove the front boat and I drove the back boat,’’ said Payne. “It’s a very narrow channel and quite difficult. But Jim would be out waving and talking to people on the banks. I’d yell at him to get back in the wheelhouse.

“He knew every inch of that river: every boat, every person. He knew the skinny on this guy and the dirty on that guy.’’

His friend was perfectly suited for the job, said Payne. He was never in a hurry and could handle whatever Mother Nature tossed his way.

“On the Miami River, you find yourself in these incredible situations, and you have to be a certain caliber of person to do this type of work,’’ Payne said. “It’s a different kind of lifestyle. One day it’s beating the heck out of you with these waves, and an hour later it’s the most beautiful thing ever.’’

What “Jim Jim’’ Ratican couldn’t handle was polluters — he’d call the Coast Guard — and the relentless encroachment of luxury high-rises on the river’s gritty banks.

“He hated the development,’’ Payne said. “He said it was putting a lot of [river] people out of work,’’ and creating a “wind tunnel’’ effect along the water.

He had particular disdain for the half-empty towers where lights on timers offered the illusion of occupancy.

“It would be 11:35 at night and Jim would do a countdown on the radio, and all the building timers would go off.’’

In 2008, Ratican took a Miami Herald reporter writing about real estate for a ride on the river.

He “eased back the throttles of the Joseph A. tugboat as he maneuvered upriver through a tight stretch lined with cargo vessels,’’ the reporter wrote. “In tow, Ratican was hauling the Betty K VII, a cargo ship from Nassau.’’