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Pacific herring play an irreplaceable role in the coastal ecosystem and food web. These small but powerful fish sustain hundreds of species, from tiny crustaceans to massive cetaceans.
Each year, during the herring spawn along British Columbia’s (B.C. ) coast, biodiversity flourishes as both marine and terrestrial life gathers for this nutrient-rich feast. For many First Nations, herring and their roe has been a vital food source for millennia, with traditional spawn-on-kelp (SOK) fisheries continuing to this day as a cornerstone of coastal culture.
In recent decades, a concerning ecological threat has unfolded due to overfishing, habitat destruction, and climate change. Spawning grounds are rapidly vanishing, and the species that depend on those annual returns suffer in this absence. Pacific herring are a foundational species in the marine ecosystem, supporting a vast network of predators and scavengers.
Research by Surma et al. highlights the critical ecological role of Pacific herring in the Northeast Pacific and the extensive network of species that depend on them. The researchers used an Ecopath with Ecosim (EwE) modelling software to simulate the effects of herring stock depletion, revealing that a collapse in herring populations would trigger significant cascading impacts throughout the pelagic food web. Many predator species, particularly those with diets composed of at least 20% herring, would experience substantial declines, disrupting the balance of the marine ecosystem.
While a near countless number of species rely on herring for survival, here are ten species that are currently experiencing the consequences of reduced herring abundance.
#1
Chinook Salmon
Chinook salmon are one of the five species of salmon on the Pacific Coast. Chinook are an iconic species in B.C., supporting both marine and terrestrial predators, as well as human cultures and economies. Pacific herring are vital to Chinook, comprising up to 62% of the Chinook diet in some areas. The consumption of herring plays a critical role in the growth, survival, and productivity of Chinook populations.
Further, herring act as a buffer to salmon predation by predators like seals and sea lions. If seals have plenty of herring to eat, they will be less likely to hunt Chinook. These predator-prey relationships are important considerations as many Chinook populations in southern B.C. are listed as threatened or endangered — and this salmon species is the primary prey for the critically endangered Southern Resident killer whales. This relationship highlights the intricate interconnectedness of the marine food web.
As a vital nutrient source, herring play a crucial role in sustaining Chinook populations. Declines in herring availability have contributed to nutritional stress in Chinook, with cascading effects that ripple throughout the entire ecosystem.
#2
Humpback Whales
Humpback whales target large aggregations of herring as a food source to fuel their migration and energy needs. Around northeastern Vancouver Island, juvenile herring make up about 50% of the diet of humpback whales.
Humpbacks have even developed a specific technique, known as “bubble net feeding,” to maximize prey capture as efficiently as possible. In cooperation with one another, humpback whales will dive below a school of herring and begin to blow bubbles in a spiral that creates a barrier to concentrate the fish. This “bubble net” restricts movement and will drive the school up towards the surface. Once complete, the whales open their mouths and lunge upwards to engulf as many herring as possible. Humpbacks have developed this technique towards nutrient dense forage fish, like herring, in order to accumulate adequate fat reserves for long migrations. This specialisation illustrates the importance of herring as a highly-valued prey source.
#3
Humans
Herring are not only vital to marine ecosystems but also to human communities. Recognised as a cultural keystone species in Indigenous societies, herring have played a fundamental role in sustenance, tradition, and economy for millennia.
The traditional Spawn on Kelp fishery is one traditional practice that exists today for many coastal nations. It involves the suspension of hemlock branches, kelp fronds, and other seaweeds in sheltered spawning areas. When harvesters collect the herring roe in this way, the adult fish are left to spawn again in the future. Such a restorative and sustainable method allows the spawning herring to live on and spawn again, therefore maintaining the herring’s critical ecosystem function.
Coastal peoples’relationship with herring and their nutritional value is believed to have contributed to the historical expansion of human populations in the Pacific Northwest. Archaeological records from up to 10,700 years ago show herring as more widespread and abundant than they are today, with herring bones found at 99% of archaeological sites from Puget Sound to Alaska. One recent study (cite) shows that today, herring continue to be used in 95% of Tlingit towns and villages during spawning season. For regions where herring are depleting, losses of this resource have meant declines in health for the people missing this foundational nutrient source.
“[W]hen we are out of herring, we are out of food”
Eating and processing herring has a long history in other parts of the world as well, so it is of little surprise that shortly after European colonisation started, rampant commercial fisheries began harvesting herring en masse in the late 1800’s to make fertilizer and fish oil. Archeologist Jesse Morin stated in an interview with Pacific Wild that from the “mid 18th century, to by the early 20th century, we’d lost 99% of everything.” In the 1960s, following decades of extremely high catches, herring populations crashed coastwide from overfishing. Today many fishing areas remain closed, and spawn has disappeared from many bays where they once were.
#4
Surf Scoters
Like many seabirds, surf scoters rely heavily on forage fish,such as herring, to maintain healthy populations.
Surf scoters will time their migration to summer nesting grounds so they coincide with annual spawning events, a phenomenon known as the “silver wave” hypothesis. Satellite telemetry and aerial surveys have revealed that scoters track the northward progression of herring spawns, spending nearly a third of their migration time at these critical stopover sites. The abundance of herring roe provides a rich and essential food source, reinforcing the deep ecological connection between these birds and herring populations.
In instances where herring are unavailable, surf scoters see significant losses in productivity and reproductive success. This link is so intertwined that seabirds are often considered as key indicators for the health of these fish stocks. Many herring spawning sites in the Strait of Georgia fall within designated Important Bird Areas (IBAs), highlighting their significance for both avian populations and the broader coastal environment. By conserving herring, we are not just preserving a single species—we are safeguarding an entire web of life that depends on them.
Surf scoters are just one example of the myriad sea birds that rely on Pacific herring. For example, common murres can rely on herring for up to 80% of their diet, particularly during breeding seasons when energy demands are high. Gulls gather in the thousands to feast on herring eggs exposed at low tide. Overall, herring is an essential supply of energy for many sea birds to meet their nutritional needs.
#5
Gray Whales
Gray whales time their coastal migratory route to spawning season, arriving just after the herring spawn takes place.
The Pacific Coast Feeding Group (PCFG) of gray whales, a small and vulnerable population of approximately 200 individuals, is currently listed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and is being considered for listing under the Species at Risk Act (SARA). This designation reflects ongoing concerns about their declining numbers and the potential threats to their primary food sources.
On the west coast of Vancouver Island, hundreds of whales arrive to feast on the eggs for the weeks between spawn and hatching. Evidence suggests these whales may be highly reliant on herring roe as a key seasonal food source. In addition to eating herring, gray whales will use suction and scraping to collect roe along the bottom of the seafloor from eel grass, rocks, and kelp beds. During the annual Pacific herring spawn, vast amounts of energy-rich roe become available in intertidal and nearshore habitats, providing an important nutritional resource—particularly in years when other prey, such as mysids and amphipods, are less abundant.
As spawning events bring a significant amount of marine nutrients to coastal waters, this is also a benefit to gray whales, as it enriches the ecosystem for additional food sources.
The potential dependence of this endangered population on herring roe underscores the broader ecological importance of Pacific herring within coastal food webs.
Given the precarious status of the Pacific Coast Feeding Group, the conservation and management of herring stocks are crucial to ensuring the long-term survival of this unique gray whale population and maintaining the stability of the coastal ecosystem.
#6
Bald Eagles
As millions of herring spawn in bays and estuaries in the Pacific Northwest, bald eagles congregate on shorelines and can be seen diving, talon first, into enormous concentrations of herring.
In coastal regions, fish comprise 70-90% of the diet of bald eagles. The nutrient-dense quality of herring supports the health of adult eagles and chick development, in preparation for leaner months of the year. On a larger scale, birds feeding on marine organisms is a vital ecological mechanism for nutrient distribution into terrestrial ecosystems.
#7
Sea Lions
Herring is a staple food for seals and sea lions, which is critical to maintaining their body fat.
Seals and sea lions are piscivores, primarily consuming fish as a major component of their diet. This dietary specialisation plays a crucial role in shaping their ecological interactions within marine ecosystems.
As a highly oily and nutrient dense fish, herring are especially important for maintaining healthy reserves of blubber for heat and energy. Without this nutritious food source, seals and sea lions risk metabolic issues, elevated mortality rates, and lower reproductive rates. For example, sea lions need to consume 60% more pollock than herring to achieve an equivalent energy intake as a herring-based diet. Nutritional deficiencies during early life stages can lead to smaller body size, which may affect competitive fitness in males and reproductive success in females. The additional energy required to consume and digest more pollock might not be feasible given the long foraging distances of Steller sea lions (up to 350 km per trip!). Nutritional deficiencies during early life stages can lead to smaller body size, which may affect competitive fitness in males and reproductive success in females. This could contribute to long-term population decline like in the Gulf of Alaska, where Steller sea lion population declined by 80%.
These losses illustrate the irreplaceable value of herring as a high quality, energy-dense food source.
#8
Halibut
Herring are a vital nutrient source for many large predatory fish, such as halibut.
In the case of halibut, herring comprise approximately 53% of their diet — particularly during herring spawning season. As large schools of herring gather near the coastline, they become an easy target. Halibut take advantage of these high concentrations of food, as their abundance makes them easy to capture. In turn, concentrations of halibut are a welcome target for hungry marine mammals and sharks.
#9
Black Bears
Herring roe are considered a substantial component to some coastal black bears’s diets, with one study showing herring roe can make up to 63% of black bear springtime diet.
While these interactions are still visible today, it is likely that bears and herring interacted even more when herring populations were more stable, widespread, and abundant.
Herring is a key nutrient for many species, as they convert high-energy plankton into food energy consumable by many predators, like salmon and bears.
Herring serve as a crucial food source for salmon, which in turn sustain black bears and contribute to nutrient cycling within their ecosystems. At the end of the salmon life cycle, salmon decay and outflow ocean-derived nutrients to river beds up and down the West Coast. In coastal B.C watersheds home to black bears, salmon provide up to 40% of the nitrogen used by plants in river based ecosystems. By nourishing the salmon that nourish forests, the ecosystems home to bears stay healthy.
#10
Sea Wolves
During the annual herring spawn, coastal wolves are often seen foraging for herring roe at low tide.
In certain regions, marine-derived prey can comprise up to 85% of a coastal wolf’s diet, highlighting their deep ecological reliance on the ocean.
Coastal wolves, often referred to as sea wolves, are highly adapted to marine-influenced environments and rely extensively on oceanic resources for sustenance in some areas. Their diet includes a diverse array of marine prey, such as salmon, seals, shellfish, and herring, which constitute a significant portion of their nutritional intake. These wolves are frequently observed along the Pacific coastline, navigating beaches and swimming considerable distances—sometimes miles—between islands in search of food.
This unique feeding behavior exemplifies the complex interplay between terrestrial and marine ecosystems, demonstrating the profound ecological connections that sustain coastal biodiversity.
