SOUTH PADRE ISLAND, Texas (AP) — Officials say 50 concrete pyramids have been sunk in the Gulf of Mexico off South Texas as part of an artificial reef to increase fish habitat.

The project, backed by the group Friends of RGV Reef, involves marine scientists in the state's Rio Grande Valley and elsewhere studying reefs and red snapper populations, the Brownsville Herald reported Friday.

The RGV Reef project features 3-ton (2.7-metric ton) concrete pyramids placed in the water Tuesday, about 8 miles (12 kilometers) off South Padre Island.

The structures, each up to 10 feet (3 meters) tall, were transported and sunk by the landing craft Lil' Mo, owned by Lil' Mo Marine Services , which donated its time and the pyramids. The structures, made by Atlantis Marine Habitats LLC, have cavities to shelter adult snapper.

Friends president Gary Glick said 42 of the pyramids were placed in groups of four to form a "trolling trail." Cinderblocks will be sunk around some of the pyramids and limestone rip-rap around others to determine which is more effective at boosting snapper productivity.

Lil' Mo has sunk about 6,000 Atlantis-built pyramids for the Texas Parks & Wildlife Department, and other entities such as the Coastal Conservation Association, which helped fund the RGV Reef project, according to Glick.

"We talk about snapper because that's where all the research is, and it's all snapper in the scientific literature," Glick said. "But we know that when we make things right for snapper, we make things right for all of the less-studied species."

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Information from: The Brownsville Herald, http://www.brownsvilleherald.com