By Kelli Dugan
MOBILE, Ala (Reuters) - Last year it was oil. This year it is jellyfish.
Fishermen and shrimpers along the Alabama and Mississippi coasts say their efforts are being hampered by a blanket of jellyfish clogging the waters of the northern Gulf of Mexico.
A year ago the same fishermen were dealing with the after-effects of the BP oil spill, the biggest offshore oil spill in U.S. history.
Tropical weather might have eased the congestion a bit, but marine experts say jellyfish-clogged waters could put a damper on fishing and shrimping into the winter.
The bloom of thousands of moon jellyfish with their tell-tale clover pattern on their bodies has almost completely halted business in the past three weeks for fisherman and bait shop owner Harry Jemison.
"I catch bait, so they're stopping me right now," said Jemison, whose family has operated Jemison's Bait and Tackle in the Heron Bay Cutoff area near Coden, Alabama for 67 years.
"It's just like a thunderstorm or a hurricane," he said on Tuesday. "It's all part of living in God's world down here."
How long the jellyfish will stick around is hard to pin down, said William "Monty" Graham, who leads the University of Southern Mississippi's marine science department.
Researchers discovered only recently that the umbrella-shaped, dinner plate-sized creatures tend to flourish in eight to 10-year cycles, he said. The current swarm is in about the third year of the latest cycle.
Graham said the duration of the bloom depends primarily on water temperatures and storm activity.
Tropical Storm Lee's prolonged churning in the gulf in early September helped open the waters a bit.
Two years ago, a similar fall blanket of moon jellyfish in the northern gulf "kind of ate up the entire white shrimp fishing season," Graham said.
"The problem we had two years ago was that (the blooms) lasted until the end of December. They usually peak around September and are gone by November, but if (the weather) stays quiet and the water stays warm, I suspect they'll stick around," he said.
Fowl River, Alabama fisherman David Caldwell said he remembers all too well how bad things got during the last peak.
"When you can't hardly get your nets into the water, it's not even worth it to go out some days," Caldwell said. "I'm not saying it's that bad yet, but if it doesn't cool off soon it could be, and I can't afford to miss too many hauls."
The biggest concern posed by jellyfish swarms is their long-term impact on fisheries management, said Graham, whose research focuses on the role jellyfish and other gelatinous plankton play in heavily fished ecosystems.
"We harvest pretty close to the margins of what the stocks can yield and still be able to replenish themselves, so any time you put a lot of pressure on early-life stages -- the egg and larvae stages -- you potentially impact the stock down the road," he said.
"We're just not sure how far down the road that impact might be realized."
The impact will vary by fish species, he said. Anchovies, for instance, are plentiful in the waters off of Alabama and Mississippi and have extended, frequent spawning seasons. Their numbers might not be affected at the same rate as red fish, which only spawn during the fall and are already recovering from the impact of overfishing.
For Kenny Beausarge, a third-generation shrimper from the Bayou La Batre area of Alabama, the jellyfish blooms have been more of an annoyance than an obstacle.
"If it's not one thing, it's something else. I'd rather deal with jellyfish than oil," he said in a reference to the 2010 BP oil spill.
(Editing by Colleen Jenkins and Greg McCune)