Pacific Coast Herring Spawn

Fishy, Fishy, Fishieee

That’s the sound my 2-year old makes whenever he sees a slippery little aquatic critter. Actually it’s more like “wishy, wishy, whitchy”. Which is possibly even cuter. While too often in my household, the iphone screen is a source of soul wrenching tirades, there are lovely moments, where focus is on the natural beauty of the non-digital world. Since it will be a couple of years until I can teach my son the joys and serenity of sailing, we have been enjoying our local wildlife. Lately that means right at the water’s edge, and getting chased around by seagulls and ducks.

And for that, this month has been pretty stellar!

If you’ve been within earshot of the water lately, you might have noticed there’s a big commotion going on. The San Francisco herring spawn is on! For fishermen, nature lovers, and our avian brothers, this is one of those large, planet scale events, and one which you can easily witness in person.

The Pacific Coast Herring Spawn

Herring Spawn on Eelgrass -CDFW

​​The herring spawn offers us a short window to see the wonders of what nature has perfected over thousands of years. And lucky for us, our watery backyard is one of the rare places on the West Coast with just the right conditions needed to host such an event. Each year starting in November, hundreds of millions of Pacific Coast Herring leave the open ocean, swim under our iconic golden gate bridge and take up residence in the bay. Apparently they sort of loiter around for a few weeks, living off of their stored fat, taking in the local sights perhaps—and then all at once, and somewhat randomly, a spawn is triggered. Over a few days, a frenzy of activity occurs! The males rush into shallower waters, spraying their milt and releasing pheromones. This signals the females each of whom lay down about 20,000 very adhesive eggs. The result is a blanket of fish roe that clings to eelgrass, kelp, rocks, pilings and yes, your sailboat’s fine hull. It’s a large, large numbers game, and good thing too because...

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On the opposite side of the food web, there are all sorts of animals that find the oil-rich herring and its eggs to be quite the tasty delicacy. Crustaceans, starfish, shorebirds and bottom feeders, feed on the high protein eggs. The spawning schools themselves are under aerial attack by dive-bombing cormorants,  guillemots, gulls and other swimming birds. From under the waves, sea lions, seals, and porpoises engage in some spirited fishing and can be seen surfacing then slipping under water, often with some surprisingly loud breathing. Even whales are known to feed on large schools of herring. True, that’s more in the open ocean than our bay, but it has been known to happen. 

Over all, the chances of surviving to the age of three, are thought to be about 50-50. Unlike salmon though, herring can reproduce each year and barring becoming someone’s dinner, live to the ripe age of ten.

Fate of the pacific herring

​The future isn’t exactly pretty, but not set in stone either. Commercial fishing and egg harvesting in the bay area is regulated. California Dept. of Fish and Wildlife (CDFW) reports that the SF Bay’s 2016-2017 Pacific herring spawning biomass was estimated at 18,300 tons. For the third year in a row, that is below the historical average 49,400 tons. Why such a dismal turnout? It is believed that the 2015-2016 El Niño event, and 2016 “Warm Blob” produced sub-optimal conditions in the northeast Pacific. Furthermore, snow melt due to 2016’s warmer spring plus a wetter winter, also reduced salinity of the Bay Area, possibly affecting the young larvae. So, yes, this year’s report (expected June) may not turn out to be the best on record, but the population numbers in the past have rebounded pretty dramatically. With one female producing about 20,000 eggs, it’s easy to understand why as Ryan Bartling, a fisheries scientist puts it, “the only predictable thing about herring is that they’re unpredictable.”

As good stewards of the world, we need to make sure the bay stays healthy. Like a nice healthy heart pumping fresh life, driving the cycle. Join us as a volunteer at our next beach clean up perhaps?

Where can I find the spawns?

To enjoy this limited time spectacle check in with our good friends at the California Department of Fish and Wildlife for reports of active sites. This year Mission Bay, Paradise Cove, Brooks Island Bird Sanctuary (Point Richmond) and even our very own Alameda rockwall have been listed as active spots. The peak is usually mid-January thru February. 
A good rule of thumb is to look for a large number of very squawky birds, diving ducks, snorting pinnipeds, and fishing boats. Oh and no doubt, you’ll hear me and my little herring saying, “here fishy, fishy, fishieee.”