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The Mississippi Sound and Mobile Bay are full of sharks this year, according to scientists who conduct surveys in area waters and fishermen who are encountering sharks even deep in the alligator-filled waters of the Mobile-Tensaw Delta.

Scientists say shark numbers appear particularly robust since Hurricane Katrina, and they speculate that the increase is partly because of limited fishing after the storms of 2004 and 2005 and increased salinity in bays and inshore waters because of a two-year drought. The drought has increased salinity in Mobile Bay, Mississippi Sound and into the Delta, expanding the range of all saltwater creatures.

The biologists say 95 percent of the sharks they encounter are smaller species that pose no threat to man. Local fishermen in the Delta have reported catching a number of sharks this summer, including in areas as far north as Gravine Island, several miles northeast of downtown Mobile.

"I'm certainly not surprised to hear that sharks are being caught above Interstate 10," said Eric Hoffmayer, a shark scientist with the Gulf Coast Research Laboratory in Ocean Springs. Hoffmayer began surveying local shark populations in 1998 and has tagged about 1,000 sharks in the last four years, working mostly inshore of the barrier islands. About 70 percent of the sharks he's encountered are juveniles, less than 3 feet long.

"Since Katrina, we've had major increases in shark populations in the nearshore areas," he said. "The Mississippi Sound is a really good nursery area. Whether there is a lot of protection from predators or a lot of food, I don't know, but there are a lot of sharks around."

The dominant species inshore are blacktips, Atlantic sharpnose, finetooth and bull sharks. The sharpnose and finetooth are small species, topping out at less than 5 feet. Blacktips may reach 6 feet and about 100 pounds, but are not considered a threat to people. The portly bull shark, implicated in most Gulf Coast shark attacks, can get up to about 6 feet but weigh as much as 600 pounds.

Juvenile bull sharks, well known for their ability to tolerate freshwater, are common in bayous and other brackish areas. Hoffmayer speculated bull sharks may head for freshwater right after birth. He said many questions remain about the early stages of their lives.

"They are 2 to 3 feet when they are born, so they would be the top predator in freshwater. There are not many things that are going to eat a 3-foot bull shark," Hoffmayer said. "Are they up there eating all freshwater fish? We just don't know."

John Dindo and Sean Powers of the Dauphin Island Sea Lab have initiated a similar tagging program for the Gulf, though they have only been collecting data for a year.

"We really have no idea what is out there in terms of our sharks. From four feet offshore to 60 feet deep, there's just no information," Dindo said. "Eric's got great data for the inshore stuff, but we're looking at the Gulf populations."

He said they were finding some of the same species as seen in the inshore surveys, but so far blacknose sharks have been the dominant species offshore. They top out at around 4 feet.

Dindo said they have caught bull sharks in Mobile Bay around the Middle Bay Lighthouse up to 250 pounds.

The four most common species in the inshore waters subsist primarily on fish, including menhaden, spot, croaker, speckled trout and hardhead catfish. Certain species, such as bonnethead sharks, always have crabs in their stomachs, while blacktips and bulls sometimes have stingrays and smaller sharks in their bellies, Hoffmayer said.

He said his work suggests some once common species, such as sand bar sharks, appear to be in decline. Like many other species, they have been heavily targeted for their fins, which command a premium in Asian markets, where they are used to make shark fin soup, considered a delicacy.

Under Alabama regulations, fishermen may keep two Atlantic sharpnose, with no size limits, and one other shark at least 54 inches long of any species except Atlantic angel, bigeye thresher, dusky, longfin mako, sand tiger, basking, whale, great white, nurse and smalltail. Those threatened species must be thrown back.

Source - AL.com