Alabama fishermen and scuba divers will receive a welcome present from the state of Alabama in a few years: the coordinates to a series of man-made coral reefs teaming with fish and other reef creatures.

In order to promote coral growth, the state has placed 100 federally funded concrete pyramids at depths ranging from 150 to 250 feet (45 to 75 metres). Each pyramid is 9 feet (3 metres) tall and weighs about 7,500 lbs (3,400 kg).

The pyramids have now been resting off the coast of Alabama for three years and will continue to be studied by scientists and regulators for a few years more before their exact location is made public.

In order to find out differences when it comes to fish-attracting power, some pyramids have been placed alone while others stand in groups of up to six pyramids. Some reefs have also been fitted with so called FADs – Fish Attracting Devices. These FADs are essentially chains rising up from the reef to buoys suspended underwater. Scientists hope to determine if the use of FADs has any effect on the number of snapper and grouper; both highly priced food fishes that are becoming increasingly rare along the Atlantic coast of the Americas.

Early settlers and late followers

Some species of fish arrived to check out the pyramids in no time, such as grunt and spadefish. Other species, like sculpins and blennies, didn’t like the habitat until corals and barnacles began to spread over the concrete.

“The red snapper and the red porgies are the two initial species that you see,” says Bob Shipp, head of marine sciences at the University of South Alabama. After that, you see vermilion snapper and triggerfish as the next order of abundance. Groupers are the last fish to set in.”

Both the University of South Alabama and the Alabama state Marine Resources division are using tiny unmanned submarines fitted with underwater video cameras to keep an eye on the reefs and their videos show dense congregations of spadefish, porgies, snapper, soap fish, queen angelfish and grouper.

“My gut feeling is that fish populations on the reefs are a reflection of relative local abundance in the adjacent habitat,” says Shipp. “Red snapper and red porgy are the most abundant fish in that depth. They forage away from their home reefs and find new areas. That’s why they are first and the most abundant.”

What if anyone finds out?

So, how can you keep one hundred 7,500 pound concrete structures a secret for years and years in the extremely busy Mexican Gulf? Shipp says he believes at least one of the reefs has been discovered, since they got only a few fish when they sampled that reef using rod and reel. Compared to other nearby pyramid reefs, that yield was miniscule which may indicate that fishermen are on to the secret. As Shipp and his crew approached the reef, a commercial fishing boat could be seen motoring away from the spot.