Creature Feature: Pacific herring Clupea pallasi
Pacific herring heading to spawning grounds in a tight school. Each fish stays in formation with by keeping a careful watch on its neighbors moves. Photo by Jacob Botter
PACIFIC HERRING (Clupea pallasi)
This month’s Creature Feature is the Pacific herring, Clupea pallasi. These are bright, silvery fish with dark blue or olive-colored backs, that reach 30-40 cm (12-20 in) and swim in schools. Scientists know from tagging and tracking fish that they stick together with their school for many years. And, they learn a lot in their schools! Recently, scientists and First Nations elders have suggested that young fish learn their way back to their spawning grounds from older fish in their schools.
COOL TO SCHOOL
Herring school in Hughes Bay, Lopez Island, WA. Photo by Cathleen Wilson
Pacific herring schools are a marvel to watch as they morph and shape-shift faster than Transformers. And schooling is also more than meets the eye. Each fish is positioned in a way that makes swimming easier for itself and its schoolmates (that’s physics!). Fish take turns at being at the front of the school, where it takes more effort to swim. Schooling helps herring avoid predators, who have a tough time singling out one fish in the great, shifting mass. But how do they know just when to turn, change speed, or even split up for a moment? Keeping a keen eye on their neighbors, each herring copies the movement, keeping its position in the ranks mainly by sight.
WHERE IT ALL BEGINS
Pacific herring pawning sites in the US part of the Salish Sea. Map by WA Dept of Fish & Wildlife 2014
Normally Pacific herring swim in schools not far beneath the surface in the deep waters off our coasts. When it comes time to spawn, they head for the deep, hugging the seafloor to keep a low profile as they move slowly landward. This helps to hide from predators, like Chinook and coho salmon, lingcod, and harbor seals en route. Then, on cue from a slight rise in water temperature and other mysterious signals, herring swim in droves to the shallows of northern Pacific shorelines, including our own shores of the Salish Sea. Like salmon, they return to the same location where they began life. These are the lucky ones; one out of about 10,000 herring survive from egg to spawner. A certain smell in the water can trigger females to lay eggs (around 20,000 each), and this starts males releasing milt. The males’ milt turns great stretches of coastlines light turquoise. Eggs are super sticky, clear, golden orbs that adhere to any and all surfaces in the shallows, from eelgrass to seaweed to rocks and even marine debris (yep, garbage). People have anticipated these spawning parties for millennia, catching the fish in their schools by sea and placing hemlock branches in the water to pull out later, caked with eggs, or harvesting egg-laden kelp to eat, kelp and all-yum!
SNICKERS BARS OF THE SEA
A school of herring breaking the surface near a hungry humpback whale, gulls, and rhinoceros auklets, working in cahoots.
People aren’t the only ones anticipating a rich, oily meal. Countless wildlife species come out of hiding to join the feast, by sea, by air, and by land! Herring are followed from the sea by humpback whales, who herd the schools into great swarms using nets made by blowing bubbles, then lunge upward through the center of the “bubble net”, mouths agape, gulping hundreds of fish at once, while gulls and other sea birds clean up the scraps. Harbor and Dall’s porpoise snatch as many as they can find. Sea lions and harbor seals join the frenzy, diving through the great balls of fish, devouring them one by one. Multitudes of diving birds, like cormorants, loons, surf scoters, rhinoceros auklets, and bufflehead, just to name a few, join the feast from above, working with the mammals below, who drive the fish closer within their reach of their quick beaks. In the intertidal zones, invertebrates benefit from the bounty. Anemones catch sinking eggs, hermit crabs and shorecrabs pick them from surfaces, and even filter feeders, like clams, suck them up through their very own straws.
Land animals get in on the buffet, too. In wilder places, bears, wolves, mink, river otter, raccoons, and many more furry and feathered friends, scour the rocky shores, munching on eggs or unlucky fish. This abundance of nutrients from the sea, can now feed even the trees of the forests, as high tides bring eggs and fish to their feet, and animals deliver convenient packages of herring-based ‘fertilizer,’ via their scat, after the feast. Just like salmon, some of the lushness of our forests is thanks to herring and their drive to reproduce on the shores of the Salish Sea. Unlike salmon, herring live to spawn again, for 5-15 years.
A school of Pacific herring stream through a bull kelp forest in the Salish Sea. Photo by Cy Scammell while free-diving
ON THE BRINK
Being so tasty comes with a price. While indigenous peoples have relied on herring eggs and adult fish for thousands of years, with careful management of their fisheries, the herring were sustained. But in the last couple of hundred years, people have caught herring commercially and sometimes in numbers too high for the population to survive. Some herring populations are now extinct; no more fish return to once-bustling spawning beaches in many parts of the Salish Sea.
SALISH SEA HEROES
Luckily, there are wise people doing science and sharing traditional knowledge on how to bring back the herring and ensure that herring continue to return to spawn far into the future. For example, Hornby Island Conservancy holds a Herring Fest each March to help educate people to do their best to ensure stable herring populations for the benefit of the whole Salish Sea food web. SeaDoc Science Director, Dr. Joe Gaydos will speak at the Herring Fest Saturday, March 7. If you go, introduce yourself as a Junior SeaDoctor!
Herring and their wild neighbors can always use another Salish Sea Hero!
