Washington (CNN) -- Wider restrictions on fishing in the Gulf of Mexico are raising fresh concerns in an industry already hard-hit by the massive BP oil spill.





With thousands of barrels of oil still spewing out of a damaged undersea well every day, the National Oceanic and Atmospheric Administration announced Tuesday that it was nearly doubling the portion of the Gulf's federal waters that are now closed to fishing. The restricted zone now pushes south and east into the heart of the Gulf -- another blow to a $2.4 billion industry already reeling from the nearly month-old spill.





For Greg Abrams, a commercial fisherman in Panama City, Florida, that means his boats are being pushed further west to chase big catch like bluefin tuna, swordfish and mahi-mahi.





"They'll have to go in somewhere else, probably around Galveston (Texas), instead of coming home," Abrams said. "That'll cause some problems, but it's better to be safe than sorry."





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Abrams owns a fleet of 14 fishing boats and hires another 41. One of them has  caught 80 tuna in a seven-day stretch off the Gulf's Loop Current, a haul he called a "great start" to a seven-month season.





"Now he has to leave the current and go farther west," Abrams said.





NOAA's latest order extends the closed zone to a nearly 46,000-square-mile stretch, about 19 percent of the Gulf. The ongoing spill now threatens to be picked up by the Loop Current, which could spread some oil around the tip of Florida and up the U.S. East Coast.





Unconfirmed reports from researchers that large amounts of oil is spreading below the surface, as well as concerns about the effect of chemical dispersants used to break up the spill, also worry people in the industry.





Deborah Long, a spokeswoman for the Southern Shrimpers Association, said fishermen could face a "multi-generational effect" on the creatures from which they draw their living, with shrimp and bluefin tuna the two species with the most to lose.





"We're not just worried about the shrimp stocks here," Long said. "We're worried about the entire marine food chain."





Many areas off the Louisiana and Alabama coasts remain open to both commercial and recreational fishing as BP, the Coast Guard and volunteers try to battle the spreading slick offshore. But news accounts of the spill have prompted tourists to cancel fishing trips even in waters that are so far unaffected, said Sonny Schindler, of Shore Thing Charters in Diamondhead, Mississippi.





"The oil hasn't done a thing to us -- it's the exposure," Schindler said Tuesday. He added, "Our water's still open, we're still trying to fish every chance we can, and we're open for business."





And some of those who are still able to get out on the water are now seeing buyers go elsewhere, said Bobby Lovell, a crab fisherman in Louisiana's St. Bernard Parish.





State-controlled waters near New Orleans were opened for three days starting Saturday, Lovell said. He and his father laid crab traps last weekend in Lake Borgne and came back with an ice chest full of crustaceans -- but he said many of his buyers have turned to suppliers in western Louisiana, which isn't currently threatened by the spill.





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"I'm stressed. I'm pacing back and forth, and I'm normally a calm guy," he said. However, "The big wholesalers are in the same predicament I am right now," he said.





The closures follow an April 20 explosion that sank the drilling platform Deepwater Horizon, taking 11 workers with it. Efforts to shut down the well that was ripped open by the accident have failed so far, though well owner BP says it has been able to capture some of the escaping oil and pump it to a ship on the surface.





"The fish will move. They have fins. They will
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