State officials are delaying the start of commercial crab season until at least Dec. 1 to protect hundreds of humpback whales that are still feeding off the California coast, marking the fourth consecutive year that the California Department of Fish and Wildlife has postponed the early November opener to avoid ensnaring the whales in trap lines. 

“There are so many whales around at this point that opening the season on time presents too great of an entanglement risk,” said Ryan Bartling, a scientist with C.D.F.W.’s Whale Safe Fisheries program. 

The delay will not affect sport fishermen: recreational crabbing will begin on time this Saturday, albeit with a total ban on crab traps and a new set of emergency restrictions on hoop nets. The rules respond to the surging popularity of the nets, which recreational fishermen turned to when traditional traps were temporarily banned for sport crabbing last year. The mesh hoops must be checked every two hours, in contrast to the nine-day service interval for traps. The new rules clarify those time intervals and ban certain trap-like nets.

Unlike other migratory species like gray whales, humpback populations off the California coast have been growing over the past decade, according to long-term assessments by the National Oceanographic and Atmospheric Administration, though some population groups remain endangered. Humpback feeding season runs from spring to fall before they migrate south to waters off Mexico and Central America. 

When C.D.F.W. staff and contractors surveyed coastal waters from planes and boats in recent weeks, they found many cetaceans lingering, gorging themselves on an abundance of krill and small fish. In the program’s Zone 3, which runs from the Sonoma-Mendocino border in the north to Pigeon Point in the south and spans the productive fishing grounds of the Gulf of the Farallones, scientists spotted 271 humpback whales during four surveys. The state will conduct another entanglement risk assessment by Nov. 23, after which crabbers will get an update on the December opener. 

The heavy distribution of humpbacks across the area, and at varying depths, made the delay inevitable, C.D.F.W. staff said. While some commercial fishermen hope new allowances for hoop nets could allow them to start crabbing on time next year, traditional crab pots are still their only legal option this year. Even a severe cap on the number of traps would not be enough to shield the many whales from entanglement, Mr. Bartling said. 

Local Dungeness crab fishermen largely anticipated the delay, and are preparing to wait even longer. Dungeness is part of holiday traditions for many Californians, and the fishing season coincides with traditional peaks in demand around Thanksgiving, Christmas, New Year’s and Chinese New Year. In the past three years, regulators have extended their initial delays until mid-December because of the continued presence of whales. But in the 2015-2016 season, high levels of toxic domoic acid forced a delay that lasted until February, erasing holiday sales.

Fishermen dread the recurrence of such a calamity, which is caused by algal blooms, and even missing Thanksgiving is a big deal. A late start can also mean that peak crabbing runs headlong into potentially dangerous January storms. 

But the crabs aren’t going anywhere in the next month, and commercial fishermen want to avoid whale entanglements as much as regulators, said Dick Ogg, a veteran crabber from Bodega Bay. Three whale entanglements in a season automatically triggers an early closure; that happened in March, closing a window that had started late to begin with. 

“The last thing we want to do is do something that reduces our opportunity,” said Mr. Ogg, who sits on the California Dungeness Crab Fishing Gear Working Group. “We want to do the right thing.” He added: “We really don’t have a choice.”

Since the state tightened rules on traps for recreational use last year, the use of hoops has exploded. Some new designs have rigid bent arms and use heavy, metallic mesh, passing as nets but functioning much more like traps. The new emergency regulations take aim at those nets, requiring them to use soft mesh. They also clarify that hoops must be checked and serviced every two hours statewide. 

Though hoop nets were mainly used for lobster in other parts of the state, Tomales Bay crabbers have used them for years. Only relatively recently did traps supplant them. “I blame ‘Deadliest Catch’ for making crabbing and crab pots more popular,” said Willy Vogler, a co-owner of Lawson’s Landing. “On opening day of Dungeness season, half the boats waiting to launch are playing ‘Wanted: Dead or Alive’ by Bon Jovi, the theme music from the show.” 

Last year, those recreational crabbers had to buy hoops, some of which Mr. Vogler said are just as effective in the short term as traps. He said he didn’t understand why regulators were barring the bent-arm hoop nets, which can catch more crabs in a two-hour window. 

“It seems to me that if your hoops held more crab and if you were crabbing in the right spot, you could be limited and done earlier, removing your hoops from the water sooner and reducing chances for a whale entanglement,” he said. “Since the whole hoop net thing is supposedly to reduce whale entanglement, I’m a little confused.”

Mr. Bartling said he understood that reasoning. “The faster they catch the crab, the sooner they’re off the water,” he agreed. “That makes sense, but ultimately we’re trying to have a very clear dividing line between traps and nets.”

California’s aggressive regulation of the Dungeness crab fishery stems from a 2019 settlement with the Center for Biological Diversity, which had sued over whale and sea turtle entanglements. Last week, the nonprofit sued the National Marine Fisheries Service, part of NOAA, to stop drift gillnet fishing, which it says has continued to trap humpbacks.