"I've been working on herring for the past decade, and it seems like more people are taking an interest in them"
Updated 5:09 pm, Thursday, January 24, 2013
Great swirling schools of herring converged in San Francisco Bay this month, drawing fishermen, sea lions, harbor seals and thousands upon thousands of birds looking to fatten up for the winter.
The menagerie of wildlife is a sign that the bay's once spectacular herring runs, which collapsed four years ago, are returning to their former glory. The San Francisco run is the last urban fishery in the United States in which people can actually sit on shore and watch commercial boats haul in the squiggling fish.
As many as 12,000 birds converged on Richardson Bay, in Marin County, this week as the herring arrived en masse to lay and fertilize eggs, or roe, a delicacy for a wide variety of species, including sushi-loving humans. Fishermen scrambled to cast their nets amid the swooping, honking, squawking hordes.
"It is such an inspiration. There is something electric about a herring run," said Anna Weinstein, the seabird program manager for Audubon California. "To have such an exciting event, especially here in San Francisco, is really cool and exciting."
The herring, which live up to nine years and can grow to more than 12 inches long, spend most of their lives in the open ocean.
They come to spawn in the bay and its estuaries in November, where they congregate in masses that, if they were all netted, would weigh more than 50,000 tons, experts calculate.
The females lay their eggs on rocks, seaweed, riprap or pilings, and the males fertilize the eggs with their milt.
Near Mission Rock
The schooling fish were first spotted Jan. 7 off Mission Rock, near AT&T Park. Hundreds of thousands of the little fish filled the bay from the ballpark to the Ferry Building over the course of a week, said Ryan Bartling, an environmental scientist who specializes in marine fisheries for the California Department of Fish and Wildlife.
The latest swarm started along the Sausalito waterfront last Friday, attracting fishermen from as far away as Washington.
"I've been working on herring for the past decade, and it seems like more people are taking an interest in them," Bartling said.
"This week, they were in Sausalito, and it was something to see. When you've got a 30-foot 'bow picker' fishing boat with birds all over, you can't miss it."
The Pacific herring fishery is important mainly for the product the fish produce, a delicacy known as golden roe, which is prized in Japan above herring eggs from other parts of the world because of its brilliant color and taste.
Fishermen generally cut the roe out of the fish or pluck it off kelp where the herring spawn. The remains of fish taken for their roe are used for pet food and chicken feed.
The arrival of the herring is a big thing, Bartling said, particularly in the wake of their nearly catastrophic decline. The number of herring seen in the bay dropped steadily starting in the late 1990s and reached a historic low in 2009, forcing the state to close the fishing season for the winter.
Scientists believe warmer water and a lack of krill and other food sources in the ocean caused the decline.
The arrival of herring is good for the fishing and sushi industries, but it is a bonanza for the marine ecosystem, where the herring are a crucial cog in the food chain, Weinstein said. Harbor seals, sea lions, porpoises, dolphins, brown pelicans, 11 species of seagulls, cormorants, scaups, scoters and grebes rush from all directions into San Francisco Bay to feast on fish and eggs during the herring run.
"It is the biggest estuarine wildlife event in the winter in California," Weinstein said.
"Everyone drops everything and feeds on herring roe. You'll see these fat gulls sitting there. It looks like Thanksgiving just happened."
This winter's herring season, which began in November and is open from 5 p.m. Sunday to noon Friday through March, has a quota of 2,854 tons of fish and roe, or 4.7 percent of the estimated weight of all of the spawning herring in the bay. In 2000, the herring quota was 5,925 tons.
As it is, Weinstein said, most of the herring in the bay are under the age of 4. The older, more valuable, fish have almost disappeared. Even the number of 4-year-old fish caught in the bay is well below the historic average, according to state biologists.
"We're deeply concerned, as is the Department of Fish and Wildlife and fishermen, about the lack of older fish," Weinstein said. "It indicates stress, but the reason is a mystery."
Peter Fimrite is a San Francisco Chronicle staff writer. E-mail: email@example.com Twitter: @pfimrite