MARATHON -- A dismal stone-crab season that may prove a calamity for the Florida Keys commercial fishing fleet surprised even crab researchers.

"There are normal dips in the fishery," Ryan Gandy, a Ph.D crustacean researcher with the Florida Fish and Wildlife Conservation Commission, said Friday.

"We had indications this might not be a stellar year," he said. "It looked like nothing to be concerned about. Then once the fishing started, the crab population wasn't there."

The harvest of stone-crab claws -- the season runs from Oct. 15 to May 15 -- ranks second only to lobster in financial importance to Monroe County's commercial fishing industry.

Typically, Monroe and Collier counties account for more than half the state's harvest of crab claws, despite the fact that stone crabs can be found off much of Florida's coast. About a third of the state's 1,200 licensed trap fishers are based in the Keys.

Last season, the Keys produced nearly 1.1 million pounds of claws -- about 41 percent of the 2.67 million pounds caught statewide.

This season has turned "bleak," Keys Fisheries General Manager Gary Graves said Tuesday. The Marathon fish house been forced to lay off staff on its production side and raise dockside prices to keep fishing crews from pulling their traps out of the water early.

Still, harvests of legal-size claws coming into the docks are a small fraction of what they should be, Graves said.

Poor harvests in the Keys are reflected along the Gulf of Mexico coast, Gandy said. "It's not specific to the Keys," he said. "We're seeing it throughout the fishery."

The state Fish and Wildlife Research Institute keeps from 80 to 100 stone-crab traps, split among four trap lines, in Keys waters to regularly survey the population.

"Our traps are showing about the same thing the fishermen are seeing," Gandy said. "It looked pretty good when the season started but then dropped."

The number of juvenile stone crabs seems to be relatively constant, Gandy noted. "We looked at whether this is an issue of the babies not coming in," he said. "As far as we can see, recruitment is about where it should be."

"There are lot of questions about the health of the Gulf," Gandy said. "If those were going to cause a problem, we'd see it first in the babies that are most vulnerable. But we're not seeing that."

Causes for the population decline remain uncertain.

The Gulf has seen two straight warm winters, which may slow crab movement. Toxic red-tide blooms have been seen off Southwest Florida.

"North of Sarasota, fishermen say they're seeing a lot of octopus, which tend to cause problems for crabs in traps or out walking around," Gandy said.

After a relatively healthy harvest in the Keys and South Florida last year, Gandy said researchers anticipated a slight decline this year.

"The dips themselves make sense," he said. "It's the magnitude that's a concern. It will take some time to see if things change."

A cold front moving into the state this weekend may help improve the catch, Gandy said.

"After a strong start to the season, it's normal to have a lull until January when there's usually a bump," he said. "Time will tell."