They dress much like their fathers and grandfathers before them, fish-stained slickers over well-worn jeans, thick gloves nicked by countless fillet knives.

And as the once-empty neighborhood around them closes in with new office towers and luxury apartments, the Seaport District’s fishmongers still make their living off the ocean.

Just often not the one that laps at the docks outside their doors.

After years of struggle in the face of a declining local fishery, the Fish Pier in Boston is again bursting with seafood businesses. But with New England fishing stocks tightly managed, the Fish Pier dealers are now more reliant on fishermen from distant oceans, their catch arriving by truck after being shipped through Logan Airport or the Conley Terminal.

“Just like a Ford has parts from different parts of the world, I think Boston is becoming this seaport hub, and that allows us to be very successful,’’ said Richard Stavis, chief executive of Stavis Seafoods, a Boston-based national seafood distributor with offices on Fish Pier.

Just a few years ago, Fish Pier was a little more than half full, the tail-end of a rocky period when its decline seemed inevitable. Today, it is nearly fully occupied with 15 tenants — part of a booming secondary trade of more than 60 seafood processing businesses in and near the South Boston waterfront.

They’ve managed to survive because of their proximity to local highways, Logan, and the Conley Terminal, which brings in massive cargo containers from all over the world.

“Fish Pier is one of the handful of places in the world where you can actually dock vessels and unload fish and have it processed. . . . That’s a big draw,’’ said Lisa Wieland, the port director for the Massachusetts Port Authority, which owns Fish Pier and the neighboring Marine Terminal where other seafood dealers are located.

But with more middlemen touching the fish before it arrives at their loading docks, the Fish Pier dealers run on much tighter margins, said Bill Mantville, 49, owner of wholesale distributor Leading Seafoods. Inside his cinderblock bay on Fish Pier, workers methodically dress and pack 5,000 to 8,000 pounds of fish each day, standing in for shifts that can stretch for 12 hours.

“Why do we still do it?’’ Mantville asked. “Well, we do it to feed our families. The work that we put in is now beyond what we get back. Our hands are getting crackly. We’re getting old.’’

Nearby are tony restaurants with rooftop bars. But inside the belly of Fish Pier, a blue-collar, working-class spirit survives, though with modern tools: RFID tags, not hand-written logs; orders phoned to Indonesia, not shouted across the dock to a nearby boat.

Conditions at Fish Pier are much improved since a decade ago when the Conservation Law Foundation sued Massport, accusing it of allowing the Pier to fall into disarray. Massport performed much-needed maintenance on facilities, and its tenants say Fish Pier is cleaner, brighter, better.

Fish Pier generated $4.7 million in revenues for Massport in fiscal 2015 and barely broke even on an operating basis, the agency said.

Looking ahead, Massport believes the massive dredging of Boston Harbor that will begin this year could bring even more business to seafood dealers and other maritime businesses in the port.

“The industry is evolving to larger and larger container ships, and we need to increase our water depth in order to handle these ships, and larger ships means more capacity for imports and exports through the Port of Boston,’’ Wieland said.

Still, Fish Pier has its limitations. Stavis said an icehouse on or near the Pier would make it easier for the dealers and remaining boats to keep the catch cold; the narrow main drag makes squeezing in semitrailers a challenge.

“In the best of all situations, there would be investment to restore some of the services that would be needed,’’ Stavis said. “Whether something like that can happen in this day and age, whether someone can come in on a white horse and make that happen — no, I don’t think so.’’

A decade ago, the seafood dealers had an uneasy view of their future, anxious they would become the next casualty of a real estate boom that has remade the surrounding blocks. But even now, with much of the Pier fixed up and in trim working order, there is concern about all the development happening around them.

In February, a group of state politicians urged Secretary of State William Galvin to add Fish Pier to the National Register of Historic Places. That would protect it from potential developers and limit its commercial usage. Wieland declined to comment on whether Massport supports the historical designation.

The older fishers think in decades and remain unsettled by where the South Boston waterfront is headed.

Clad in a stained sweatshirt and jeans, Sal Patania, owner of wholesaler and retailer Ideal Seafood, Inc., looked the part, perched inside his cramped office on the Pier. Between barking out orders — 10 pounds of haddock here, a case of salmon there — the 35-year industry veteran answered the phone with a sing-song, half-whistle of a hello: “Ideal!’’

His company once had as many as 40 workers; he’s down to six full-time employees. Like many here, Patania relies on fish from elsewhere — about 75 percent of his product is shipped in from overseas.

“It’s going to happen,’’ Patania warns of the Pier being redeveloped. “Oh, it’s going to happen. Yeah, sooner or later.’’

94%

Occupancy rate on the Fish Pier, compared with

65%

in 2013

Michael Bodley can be reached at michael.bodley@globe.com. Follow him on Twitter @michael_bodley.