How did a school of decorative carp come to live in the waterlogged cellar of a blighted former shipbuilding storehouse in the Philadelphia Navy Yard?

As with any good fish story, it depends on whom you ask.

The white and orange-red fish — most just a few inches from mouth to tail, but some said to reach a foot — reveal themselves to fans and passersby when they swim through the rust-corroded metal door to the basement of Building No. 624 into a sunken outdoor stairwell.

Some speculate that their forebears were introduced to the eight-story building on Kitty Hawk Avenue at 12th Street as a form of insect control, as occurred a few years ago at an abandoned shopping mall-turned-accidental-hatchery in Thailand.

Others wonder whether the creatures are somehow related to the koi who swim in a pool under the gaze of a watchful Buddha in one of the restored factory buildings that make up the clothing chain Urban Outfitters Inc.'s headquarters in another section of the former South Philadelphia military complex.

Another guess is that someone noticed the 77-year-old structure's perpetually flooded cellar and decided it would be a good place to empty an unwanted aquarium. Freed from the confines of a fishbowl, the thinking goes, those creatures' offspring fattened into the large specimens that swim there today.

"There's the question of 'How did they get there?' "said Sarah Novak, 32, of South Philadelphia, who has been checking on the fish since she started work about three years ago as a logistics specialist with a Navy division that remains on the former base, now owned by the city. "Everyone who knows they're there stops and looks at them."

Onlookers view decorative carp living in the waterlogged basement of a building in the Philadelphia Navy Yard.
Jacob Adelman / Staff
Onlookers view decorative carp living in the waterlogged basement of a building in the Philadelphia Navy Yard.

Seeing colorful carp swim through the bowels of a blighted building could be seen as epitomizing the incongruous vibe that has settled on the Navy Yard about 13 years after the first new offices opened at the decommissioned military station. It's a place where high-end lab and office buildings designed by international architects stand beside long-vacant colonial-era barracks and aged former manufacturing plants.

"What I love about the Navy Yard are the eccentric juxtapositions that don't exist anywhere else," said Prema Gupta, senior vice president for Navy Yard planning and development at the Philadelphia Industrial Development Corp., which manages the property for the city.

The former base's Corporate Center section is home to such companies as the British pharmaceutical giant GlaxoSmithKline PLC, the Chinese biotech firm WuXi AppTec Inc., and the homegrown investment bank FS Investment Solutions LLC. In its industrial zones, Philadelphia Shipyard Inc. continues to build seafaring vessels (for now), Tasty Baking Co. turns out Krimpets and sweet rolls, and RevZilla.com readies motorcycle gear for online sales.

Yet large swaths of the Navy Yard's 1,200 acres are still made up of abandoned buildings dotting empty lots.

Building No. 624 — the one with the fish — was once used to store shipbuilding components for later assembly a few blocks away in the former manufacturing buildings that Urban Outfitters now partly occupies, Gupta said.

It and another nearby industrial building — No. 83, at 13th Street and Kitty Hawk Avenue — were highlighted in Philadelphia's bid to host Amazon.com Inc.'s planned second headquarters as properties that could be quickly developed into offices for the e-commerce giant if it selects the city and wants its new campus in the Navy Yard.

Building No. 624 at the Philadelphia Navy Yard, with Building No. 83 in the background. Both former industrial buildings are highlighted in Philadelphia’s bid to host Amazon’s planned second headquarters.
Jacob Adelman / Staff
Building No. 624 at the Philadelphia Navy Yard, with Building No. 83 in the background. Both former industrial buildings are highlighted in Philadelphia’s bid to host Amazon’s planned second headquarters.

Before Amazon's search for a second headquarters, PIDC officials contemplated turning the structures into apartment or condo buildings, based on an engineering study that determined both are sturdy enough to support additional floors.

The fish live in an 800-square-foot portion of  Building No. 624's basement that has remained waterlogged because of a malfunctioning plumbing system, according to the study.

"The fish are a bit of a spectacle but in no way indicate the building is compromised in any way," Gupta said.

Gupta said the fish were already in the building's cellar when she began working at the Navy Yard about three years ago. She's never heard any dependable explanation of where they came from and didn't know how many there were.

As for what kind of fish they are, real estate developer and parking magnate Joseph Zuritsky — who also happens to be the city's resident expert on decorative fish species — has a guess.

Zuritsky is chairman and chief executive of Philadelphia's Parkway Corp. but also until recently owned and operated one of the nation's leading koi farms, Quality Koi Co. in Carneys Point, N.J. After looking at a photo of the Navy Yard fish, he said that they appear to be goldfish, rather than koi, due to their body shape and lack of patterning on their scales.

Both are members of the carp family, but goldfish are better suited for surviving winters in a frigid basement with a spotty food supply than koi, which Zuritsky said was another clue to the basement dwellers' breed.

Goldfish "are much hardier than koi," he said. "You can freeze them alive in an ice cube and then thaw them out and they'll still be living."

The fish likely subsist on algae that can grow in parts of the stairwell that get sunlight.

None of the fish's fans at the Navy Yard seemed all that concerned about their breed on a recent afternoon around lunchtime, when clusters of onlookers sporadically convened to peer over the fence surrounding the flooded basement stairwell.

"I just thought it was interesting," Chichester resident Kyle Tyson, 24, said as he spent a few moments tossing bits of bread to the fish. He learned about them from a Navy Yard coworker. "I like fish anywhere."

Chichester resident Kyle Tyson feeds the decorative carp living in the waterlogged basement of a building in the Philadelphia Navy Yard during a lunch break.
Jacob Adelman / Staff
Chichester resident Kyle Tyson feeds the decorative carp living in the waterlogged basement of a building in the Philadelphia Navy Yard during a lunch break.

Architecture writer and futurist Geoff Manaugh, author of the online BLDGBLOG, characterized the basement fish as an artifact of "the cycle of ruin and redevelopment that goes through cities."

Manaugh, based in Los Angeles, said the Navy Yard fish site's allure is similar to that of other enticing urban ruins, such as the rail tracks up the west side of Manhattan before they were developed into the High Line and the grand vacant buildings that stand in Detroit.

Local examples would be the undeveloped portions of the tracks north of Center City that backers hope will someday be part of the city's own Rail Park and the former coal-loading pier on the Delaware River in Port Richmond known as Graffiti Pier.

"It's almost like a feeling that someone is pulling away a curtain and showing a part of the city you didn't realize was there," Manaugh said. "It has a feeling like a stage set or a dream or a kind of surrealism."