Dungeness crab season is approaching in the Bay Area, along with all the rituals that come with it — the crab feeds and holiday dinners piled with crab legs, sourdough bread and crocks of melted butter.

Unfortunately, there’s another, more recent local tradition that is also back: uncertainty about whether algal blooms will delay the season.

Domoic acid is the naturally occurring toxin caused by algal blooms that delayed the past two Dungeness crab seasons. According to test results from the California Department of Public Health, elevated levels of the toxin have shown up in samples of Dungeness crab collected in recent weeks at several North Coast ports.

However, the agency said it’s too soon to say whether domoic acid will delay the commercial Dungeness fishery, due to open Nov. 15.

“Based on sample results and environmental conditions, a decision will be made closer to the opening of commercial Dungeness crab season,” a representative from the California Department of Public Health said in an email.

In the meantime, the recreational Dungeness season, which is regulated differently than the commercial season, is scheduled to start Saturday. The Department of Public Health could issue a health advisory on the sport season; for example, they may recommend that sport fishermen remove the viscera, or guts, from the crab before cooking, since that’s where domoic acid concentrates.

Domoic acid is already causing problems along other parts of the West Coast. The recreational crab fishery in southern Oregon is closed due to unhealthy levels of domoic acid, as is the commercial spiny lobster season in a small part of Ventura and Santa Barbara counties.

While the recreational crab season opens all at once along the California coast, the commercial crab season opens in two parts.

The section that is due to open Nov. 15 includes the area from the Sonoma-Mendocino county line to Point Conception in Santa Barbara County, where recent tests of Dungeness crab have not shown dangerous levels of domoic acid. On Friday, at a hearing of the Joint Committee on Fisheries and Aquaculture in Eureka, David Mazzera, chief of the food and drug branch of the California Department of Public Health, said that the department had completed preseason testing for that portion of the coast.

It’s a different story north of the Sonoma-Mendocino county line, where the commercial season doesn’t normally open until Dec. 1. This month, elevated domoic acid results — more than the federal action level of 30 parts per million — have shown up in six different Dungeness crabs collected near Fort Bragg, Eureka and Crescent City (Del Norte County).

Caused by the alga pseudo-nitzschia, domoic acid made news over the summer, when sea lions were washing up near San Luis Obispo with seizures and other symptoms after eating fish or shellfish tainted by the toxin. The algal blooms that create domoic acid can be common in spring and summer, but usually go away as water temperatures drop in late fall. Among other factors, abnormally warm water temperatures over the past few years, partly because of a strong El Niño, have caused the toxin to show up in marine mammals and shellfish more often than usual.

Uncertainty and delays to the commercial crab season because of domoic acid have created upheaval in the California fishing industry. During Friday’s hearing in Eureka, State Sen. Mike McGuire discussed the impact of the unusually low catch of king salmon, Dungeness crab and sea urchin in recent years, as well as the state’s multiyear sardine fishery closure due to its historically low population.

“California’s formerly robust fisheries are now facing an unprecedented crisis,” McGuire said. “Thousands who depend on a healthy fishery continue to struggle to make ends meet.”

In August, McGuire issued a bill requesting that the 2016 and 2017 salmon seasons be declared a fishery disaster so that fishermen could receive financial aid. The same sort of disaster proclamation has already been made about the 2015-16 West Coast Dungeness season, which allows affected businesses to apply for federal relief.

Tara Duggan is a San Francisco Chronicle staff writer. Email: tduggan@sfchronicle.com Twitter: @taraduggan