Each winter, a strange natural spectacle takes over San Francisco Bay. You’ll see evidence of it: moving rafts of agitated birds; long strings of cormorants; pods of sea lions; plunge-diving pelicans. You may even see clusters of tiny translucent eggs clinging to errant strands of eelgrass that have washed up on the shore. What you won’t see is the cause for all this excitement: thousands of herring riding in on the tide, en route to their favorite spawning grounds.
The Pacific herring is a small, slender, silver schooling fish, often lumped in with other “baitfish.” Herring form enormous shoals in the open ocean, where they spend most of their lives, but once a year they return to the sheltered estuaries that hatched them so they can spawn themselves. Unlike an anadramous species like salmon, herring can spawn year after year. They prefer shallow estuaries like Richardson Bay.
A spawning event is a synchronized orgy. Males release sperm, called “milt” in a swarm that clouds the water milky white. This stimulates the females, which deposit their eggs in adhesive strips that stick to whatever substrate they happen to pass. Although herring prefer eelgrass, they will also spawn on Gracilaria, a twiggy maroon-red algae, or man-made substrates such as pier pilings and even rip-rap.
- Diving brown pelican. Creative commons photo by Ingrid Taylar.
A large female herring can produce up to 50,000 eggs. For local predators, a fish bulging with roe is one of the most nutritious meals around, so it’s no wonder that many different species take advantage of the fleeting bounty. Cormorants, sea lions, and harbor porpoises feed on the fish; sturgeon, gulls, and surf scoters gorge on the eggs. Everyone wants a piece of the action, including fishermen.
For San Francisco Bay’s herring fishermen, this season was short and sweet. Dan Yoakum was one of about 50 permit-holders out on the Bay this January. He and his fellow gill-netters reached their quota of 1,900 tons before the end of the month, less than four weeks after the season opened. Yoakum was pleased with this year’s catch, though he called the quota set by the California Department of Fish and Game “modest.” That quota allowed the fleet to catch 5 percent of the estimated total herring biomass.
“The fishery can take a lot more than that,” he says, “but that’s just what we’re doing right now.”
San Francisco Bay’s herring fishery is a “sac-roe” fishery; in other words, it’s all about the eggs. Almost all of the catch goes to Japan. The ovaries are removed from female fish and the skeins of delicate, pale golden roe are sold as “kozunoko,” a delicacy consumed on New Year’s. The Japanese eat Kozunoko, which means “many children,” as a sign of good luck and fertility, much as people in the southern U.S. eat black-eyed peas.
Herring prices fluctuate as much as the fish population. In recent years prices for the specialty product have reached record low, around $300 a ton, down from high of over $2,000. According to Yoakum, it’s a simple matter of supply and demand: Alaska fishermen have flooded the market. The combination of low prices and low quotas caused many of the 400 San Francisco Bay permit-holders to opt out, but Yoakum, a life-long fisherman who also fishes crab and abalone on the North Coast, says he’ll be back next year.
Fishery managers have had good reason to be cautious. Herring numbers tend to fluctuate, but recent years have showed a disturbing steady decline. They reached an all-time low in the 2008-’09 season, and last year Fish and Game decided to close the fishery altogether to allow stocks to recover.
According to Ryan Bartling, a Fish and Game biologist who assesses the “spawning biomass” each season, the dismal numbers were most likely linked to many factors, including an anemic krill supply offshore and higher than normal salinity in the Bay (because of the drought, which reduced freshwater flows). The November 2007 Cosco Busan oil spill, just before the 2008-’09 spawn, may have added insult to injury. Preliminary studies show that herring embryos taken from oiled sites suffered severe heart and spinal deformities.
Still, the herring appear to be bouncing back.
“We had a decent season last year, following two of the lowest biomass estimates ever,” says Bartling.
He has seen enough fish to claim this season will “far and away exceed last year,” though he won’t turn raw data into a biomass estimate until after the season ends. So far, he says, this winter’s spawning events have reached “far and wide.” In addition to the usual numerous spawns in Richardson Bay, the fish have also spawned “heavily” along the San Francisco waterfront and near Point Richmond. Though that’s reason to be cautiously optimistic about the herring’s resiliency, Bartling says his agency will keep the quotas conservative for the next few years.
“I can’t imagine going over ten percent,” he says.
Anna Wenistein, seabird program manager for California Audubon, says she wonders if that goes far enough. She has been studying the correlation between herring and wintering waterbirds and is concerned not only about San Francisco Bay’s herring population, but the status of the species in general. Historically, California has supported runs in Tomales and Humboldt Bays, but in recent years only the San Francisco Bay fishery has remained viable, and just barely.
This year’s quota was set based on last season’s spawning surveys. Even though the numbers have rebounded, they’re still below average. And there still seems to be a disproportionate number of younger fish in the population, according to Bartling. Fish and Game managers refer to this as a “truncation of age classes.” A typical management strategy is to target bigger (and older) fish, which allows younger fish to spawn multiple times. However, with the dearth of these elders, pressure on younger fish has increased.
In light of the importance of herring as a key prey species, Weinstein would like to see the fishery closed for a least a few more years to allow stocks to recover and see if the age class structure returns to a more healthy condition.
Richardson Bay includes some of the herring’s most popular haunts; in fact, gill-netters are not allowed to fish there at all, to protect vital spawning habitat. All the more for the birds.
The Richardson Bay Audubon Center has been conducting annual winter waterbird surveys in the sanctuary (which comprised 900 underwater acre in the northeast corner of Richardson Bay) since 2006. This season has yielded record-breaking numbers. According to Kerry Wilcox, the RBAC Sanctuary Manager who coordinates the surveys, observers counted over 12,000 birds on January 10 and over 13,000 on January 24. To put these numbers in perspective, the old record was 9,300 birds in 2009-2010 season. The most abundant species were greater and lesser scaup, followed by buffleheads, ruddy ducks, cormorants, American coots, and various species of gulls.
Wilcox acknowledges that the surveys at best provide a “snapshot” of what’s in the sanctuary at a given time, and while he cautions against drawing definite conclusions, he says he’s interested in comparing survey results with spawning events. For instance, there’s no denying that this season’s record-breaking January numbers coincided with heavy spawning activity.
Meanwhile, the herring spawning season isn’t over. Schools may continue entering the Bay through March and even into April. Bartling says there’s a school offshore right now, waiting to head in on the high tide.
The birds will be waiting.
And speaking of birds, check out this great video of hundreds of gulls feasting on herring roe near Point Richmond.
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For a lesson in food chain dynamics, go ahead and observe a fruiting toyon bush this winter.
Wildlife: Birds, Mammals, Fish