North Carolina dumped 7,200 tons of discarded concrete pipe onto bare ocean floor at AR-165; the reef later grew to include 3 retired tugboats for fish habitat

When we think of reusing unwanted items, we generally think of landfills and scrap yards. However, when marine biologists from North Carolina think of reusing items like an old tugboat and concrete pipes, they think of an underwater housing estate. In 2020, two tugboats, the American (88 feet, sunk in January) and the America (104 feet, sunk in April), were sunk into the sea to create an artificial reef.

According to the North Carolina Department of Environmental Quality, 7,200 tons of concrete pipes were also placed into the water, creating the AR-165 site. One more tugboat, the Valley Forge (108ft), was sunk in 2021. Although it might seem strange to create a community using a tugboat, the use of artificial reefs is actually quite a popular topic in science. So what makes up this reef, what lives there, and what do we still need to learn?

What lives in a pile of pipes?


A lot of fish. Per the same NC DEQ source, the large vertical structures created by the tug boats provide habitat for bait fish and predatory fish such as the greater amberjack and Spanish mackerel. The concrete pipes also mimic natural rock structures, meaning that benthic fish such as gag grouper, black sea bass, and gray triggerfish are found there. In September 2022, another 532 concrete reef balls were placed to fully enhance the reef. Think of it as a skyline to the reef: tugboats as high-rise buildings, concrete pipes as low-rises, and reef balls as the blocks in between.

The tropical fish angle

According to a 2019 study titled “Artificial reefs facilitate tropical fish at their range edge,” carried out by Paxton and colleagues and published in the journal Communications Biology, 30 reefs were surveyed by divers around North Carolina. They found that tropical and subtropical fish were more abundant, with higher biomass on deep artificial reefs (25-35 m).

However, temperate species were more abundant on natural reefs. The authors suggest that these structures may help fish migrate towards the poles. It should be noted, though, that these surveys were carried out before AR-165 was created. This means that this research looked at general artificial reefs in North Carolina rather than AR-165 specifically.

Do reefs create fish, or just collect them?

This has been debated by scientists for decades. A 1997 research article titled “Do Artificial Reefs Increase Regional Fish Production? A Review of Existing Data,” by Grossman, Jones, and Seaman, in the journal Fisheries, found that there was limited research showing that artificial reefs actually increased local fish production. However, they state that creating reefs may cause increased effort and increased catch rates. As this research is now decades old, it should be read as a snapshot of the state of the science at the time, not a final word.

More recent work tells a fuller story. A 2020 review by Paxton and colleagues, “Meta-Analysis Reveals Artificial Reefs Can Be Effective Tools for Fish Community Enhancement but Are Not One-Size-Fits-All,” published in Frontiers in Marine Science, analyzed 39 studies and found that artificial reefs often support fish communities comparable to natural reefs, though the outcome depends heavily on geographic location and the materials used.

The takeaway

North Carolina’s reef program is unusually large and active compared to most states; the Division of Marine Fisheries maintains roughly 68 artificial reefs along the coast, but AR-165 stands out even within that program for combining sunken vessels, concrete pipe, and reef balls at one site. Another reef, AR-305, is also popular with anglers and divers along the east coast. The fish, at least, are clearly there; what’s still unsettled is whether these structures are genuinely boosting fish populations or simply concentrating fish that were already in the area. Either way, these reefs are a good reminder that what we throw away doesn’t always have to be gone for good.