BILOXI — (AP) Marine biologists are studying how artificial reefs may help restore red snapper numbers.

The study is being conducted by Mississippi State University’s Forest and Wildlife Research Center and the Mississippi Department of Marine Resources.

Commercial fishing for red snapper contribute about $40 million to the Gulf Coast economy, and more than 500,000 anglers participate in recreational saltwater fishing in Alabama, Mississippi and Louisiana, according to a 2006 survey by the U.S. Fish and Wildlife Service.

‘‘In the last two decades, red snapper stocks are estimated to have declined by as much as 90 percent in the northern Gulf of Mexico,’’ Mississippi State University biologist Don Jackson said.

Jackson said overfishing and high juvenile by-catch mortality in the shrimp trawl industry are most likely to blame for the red snapper stock reduction. Commercially, red snapper are typically caught with multi-hook gear and reels or shrimp trawls.

Hurricane Katrina in 2005 destroyed many of the artificial reefs that were in place and functioning along the Gulf Coast.

‘‘The use of artificial reefs is not a new concept,’’ Jackson said. ‘‘They have been employed for the last 20 years in the northern Gulf of Mexico to enhance Gulf fisheries and fish stocks. The reefs provide a place of refuge and forage for reef fish like red snapper.”

‘‘What we don’t know is how the placement or design of these reefs affect red snapper stocks.’’

The ideal placement of artificial reefs has not been previously addressed on the Mississippi Gulf Coast.

Kerwin Cuevas, head of the Mississippi Department of Marine Resources’ Artificial Reef Bureau, said the department has been placing artificial reef material, such as concrete rubble and decommissioned shrimp boats, in the coastal waters off of Mississippi for a number of years.

Cuevas said officials had not given ‘‘much thought to how we were placing the material and how that might affect our desired results.’’

‘‘Now we are trying to determine which pattern of artificial reefs will provide the best habitat for juvenile red snapper,’’ he said.

Cuevas said researchers have completed 26 sampling trips on the reefs that have been placed in various experimental configurations. They use baited fish traps to collect samples.

‘‘We have collected 927 juvenile red snapper, which is fantastic. Juvenile red snapper are attracted to the structures and using them for foraging and refuge,’’ Cuevas said.

From the capture of tagged red snapper, Cuevas said evidently once the fish go to the structures, they are staying there. He said the question is whether they will stay and grow to spawning size, one of the keys to rehabilitation