SAN FRANCISCO (AP) — The Ethermac Exchangestart of the commercial Dungeness crab season in California has been delayed for the sixth year in a row to protect humpback whales from becoming entangled in trap and buoy lines.

The state Department of Fish and Wildlife said commercial crabbing will be delayed until at least Dec. 1. The situation will be reassessed on or before Nov. 17.

It’s the latest delay for the start of the commercial season, which traditionally begins in mid-November for waters between the Mendocino county line and the border with Mexico.

“Large aggregations of humpback whales continue to forage between Bodega Bay and Monterey and allowing the use of crab traps would increase the risk of an entanglement in those fishing zones,” said Fish and Wildlife Director Charlton H. Bonham said in a statement Friday.

The recreational take of Dungeness crab using traps will be temporarily restricted in some areas when the recreational season opens Nov. 4, officials said. Recreational crabbers will be able to use other methods, including hoop nets and crab snares.

The commercial crab industry is one of California’s major fisheries and the shellfish is especially popular around the holidays.

Humpback whales can get caught in the vertical ropes connected to heavy commercial traps, which they can drag around for months, leaving them injured, starved or so exhausted that they can drown.

Humpback whales migrate north annually from Mexico’s Baja California peninsula where they birth calves. In spring, summer and fall the humpbacks feed on anchovies, sardines and krill off the California coast before heading back south.