1978, Massachusetts developed a 127-acre reef of 2,500 concrete-filled tire bundles in Nantucket Sound; a 2019 survey found fish arrived in about 33 seconds at reefs versus nearly eight minutes over bare sand

Nearly 50 years ago, officials from Massachusetts placed tons of tires on the bottom of the Nantucket Sound to create homes for marine life. Decades later, scientists went back to see if it worked. According to a 2020 study published in the journal Estuaries and Coasts, it did. Researchers from Northeastern University and the Massachusetts Division of Marine Fisheries have compared fish behavior at four locations in the Sound and found that fish showed up on camera 93.4% faster in places with reef structures than in locations with open sand. This finding adds to a longstanding discussion within marine biology: do artificial reefs actually increase fish populations or do they simply attract fish from their natural environment?

A tire reef built in 1978, still standing strong

The study, ‘Comparison of Artificial and Natural Reef Productivity in Nantucket Sound, MA, USA,’ notes that the older of the two artificial reefs sits off Yarmouth. Established in 1978, the reef covers 127 acres and contains 2,500 reef modules made by packing three to five tires into concrete-filled bundles. According to the research paper, another artificial reef, which is slightly younger, was built in 2016 in Harwich and contains 1,600 yards of concrete rubble. Both reefs occupy areas where the ocean floor was originally flat and didn’t have any structure. Because Nantucket Sound’s floor is generally sandy, scientists have noted that any sort of hard surface attracts marine life looking for shelter, food, or protection from predators.

How scientists tracked the fish

As the researchers describe it, the team conducted surveys using baited underwater cameras, known as BRUVS, which stands for Baited Remote Underwater Video Surveillance, from June to September 2019. They dropped the cameras containing chopped mackerel into the water at four locations: the Yarmouth reef, the Harwich reef, the natural rocky reef, and the area with bare sand, five kilometers away from any reef. This method avoids disturbing the seafloor and can catch footage of species that are otherwise hard to spot.

Fish arrived faster near reefs, but variety stayed about the same

Fish were found approaching the reefs in about 33 seconds on average, while in the unstructured sand environment, it took them more than eight minutes to reach the area, arriving roughly 33 seconds versus roughly 502 seconds, a 93.4% reduction in the time it took fish to show up. The study's authors noted that this means that fishes gather where there is structure, either because they come from somewhere else or because they have grown up on the reef itself. The data show that species richness barely changed between reef types. The natural reef and both artificial reefs hosted a similar mix of around three fish species per site on average, above the bare control. That suggests fish move fairly freely across the Sound no matter what kind of structure they find.

Age mattered more for fish numbers. The researchers found that black sea bass, which is a commercially important species in New England, had a population 103.7% higher in number on the 41-year-old Yarmouth reef than on the 4-year-old Harwich reef. This finding matches a trend noted by reef scientists: young reefs may attract adult fish quickly but can take time to develop into juvenile-friendly habitats.

Attraction or production? A question fisheries managers still weigh

Marine biologists have long debated whether artificial reefs increase fish numbers or simply concentrate existing fish, a distinction that matters for fisheries management. A separate study published in PLOS ONE titled 'Fish Assemblages on Estuarine Artificial Reefs: Natural Rocky-Reef Mimics or Discrete Assemblages?' analyzed artificial reefs in estuarine environments of Australia and found that fish communities living on man-made structures were usually different from natural reefs and attracted a new variety of fish instead of mimicking them. While that study looked at a very different climate and ecosystem than Nantucket Sound, it illustrates a broader pattern seen across artificial-reef research: artificial reefs are not exact substitutes for natural ones, but can add habitat complexity to the ecosystem. According to NOAA's Ocean Service, artificial reefs have been built over the years using many types of structures, including decommissioned vessels, oil rigs, concrete blocks, and tires, largely because they attract fish to a known location, a benefit to commercial and recreational fishing, though scientists still debate whether that reflects new fish production or simply fish drawn in from elsewhere.

Why an old tire reef still matters today

The study also highlights the fact that the Yarmouth reef has endured seven hurricanes and tropical storms since 1978, including Gloria and Bob, without any documented movement of the tire bundles. The concrete filling appears to have kept the structure in place, and marine life has developed there over more than four decades. A reef built nearly 50 years ago is still in place today and continues to support local marine life.