Overview
AT A GLANCE
- Common Name: Pacific Herring
- Scientific Name: Clupea pallasii
- Category: Fish
- Subcategory: Ray-finned Fish
- Size: Length: 20-33 cm (8-13 in); Maximum recorded length: 46 cm (18 in)
- Weight: 0.2-0.5 kg (0.44-1.1 lb)
- Lifespan: 8-12 years (exceptionally up to 15 years in northern waters)
- Diet: Planktivorous: euphausiids (krill), copepods, amphipods, mysids, and larval fish
- Habitat: Inshore coastal waters, fjords, estuaries, and open continental shelf seas down to 250 meters depth
- Range: North Pacific Ocean: from northern Baja California and Alaska across the Bering Sea to the Sea of Okhotsk and northern Japan
- Conservation Status: Least Concern (IUCN Red List)
The Pacific Herring (Clupea pallasii) is an ecologically dominant and culturally foundational marine schooling fish that drives the productivity of the entire North Pacific rim. Ranging from the temperate estuaries of California and British Columbia through the storm-tossed Gulf of Alaska to the Siberian Arctic, this shimmering silver clupeid forms immense pelagic shoals. For thousands of years, coastal Indigenous nations have revered the Pacific herring, building prosperous maritime civilizations around sustainable harvests of herring and their nutrient-dense roe.
Ecologically, Clupea pallasii is recognized as the ultimate keystone forage fish of the Pacific Northwest marine ecosystem. Each spring, colossal spawning runs bring hundreds of millions of herring into shallow coastal bays and kelp forests, triggering a feeding frenzy of epic proportions. The arrival of spawning herring attracts humpback whales, orcas, Steller sea lions, harbor seals, bald eagles, and salmon. Their dense blankets of adhesive eggs provide an indispensable nutritional windfall that fuels coastal food webs from Alaska to Puget Sound.
Biology and Physical Characteristics
The Pacific herring possesses a streamlined, fusiform body characterized by brilliant silver sides, a dark blue-green metallic back, and large, smooth cycloid scales that shed easily when handled. It is distinguished from the Atlantic herring by its fewer vertebrae (typically 51-55 compared to 56-59) and differences in the ventral keel scales behind the pelvic fins. Its vision is optimized for detecting tiny planktonic crustaceans in dim coastal waters, and its inner ear is connected to the swim bladder via specialized fluid-filled ducts, granting acute low-frequency hearing used to detect incoming predators.
Behavior and Ecology
Pacific herring undergo extensive seasonal migrations between deep offshore feeding zones in summer and sheltered inshore spawning bays in late winter. During coastal spawning events, entire bays turn milky-white as males release billions of sperm (milt) simultaneously. Females deposit billions of extraordinarily sticky eggs that coat eelgrass beds, rock surfaces, and giant kelp fronds in layers several inches thick. After spawning, the adult fish retreat back to continental shelf waters, leaving the fertilized eggs to hatch into free-swimming larvae in two to three weeks.
Conservation and Human Impact
Assessed as Least Concern globally by the IUCN, Pacific herring populations nevertheless exhibit severe localized depletion. Commercial overfishing in the mid-to-late twentieth century, compounded by industrial disturbances and the 1989 Exxon Valdez oil spill in Prince William Sound, caused prolonged stock collapses from which certain regional populations have struggled to recover. Contemporary management emphasizes protective roe-on-kelp harvesting, eelgrass restoration, and strict fishing closures to allow depleted spawning aggregations to rebuild.
Interesting Factoid
During the peak of the Pacific herring spring spawning run, male herring release so much reproductive milt simultaneously that coastal bays and fjords appear milky-turquoise from high-altitude aircraft and satellite imagery.