Herring are small, schooling fish found in vast numbers across the world’s oceans. Atlantic herring (Clupea harengus) stands as one of the most abundant fish species globally, forming immense schools on both sides of the North Atlantic. Similarly, Pacific herring (Clupea pallasii) are widely distributed throughout the Pacific Ocean. These fish play a foundational role in marine ecosystems, serving as a critical link in the food chain.
Understanding Herring Conservation Status
Herring conservation status varies significantly by species and, more importantly, by specific regional populations, known as stocks. While the Atlantic herring species as a whole is classified by the IUCN as “Least Concern,” this designation masks a complex reality for individual populations.
For instance, the Gulf of Maine Atlantic herring stock is currently considered overfished, although fishing pressure is not leading to further overfishing. Its spawning stock biomass is notably low, sitting at 26% of its target level, and poor recruitment of new fish has been a persistent concern.
In contrast, the North Sea herring stock is currently in good condition, with fishing mortality rates below levels that would maximize sustainable yield, and the spawning stock size remains above target levels. Despite this, the North Sea stock has experienced a decline since 2016 due to reduced reproductive success, prompting a recommended 22.5% cut in the total allowable catch for 2025.
The situation is more concerning for Western Baltic Spring-Spawning herring, which is highly depleted and subject to a zero-catch recommendation for 2025. This stock is often inadvertently caught as bycatch in other fisheries, complicating its recovery.
Atlanto-Scandian herring populations have seen a substantial decline from 7 million metric tonnes in 2008 to 3.7 million, with catches frequently exceeding scientific advice. Continued overfishing could lead to a critically low level by 2026, echoing a significant collapse in the 1960s.
On the Pacific side, the Pacific herring species is categorized as “Data Deficient” by the IUCN, indicating insufficient information to assess its risk of extinction. Many Pacific herring populations in British Columbia have reached historically low levels, though the Strait of Georgia remains a vital stronghold. Some stocks are showing signs of recovery, while others continue to decline, highlighting the diverse status of herring worldwide.
Key Factors Affecting Herring Populations
Herring populations face several significant challenges. Historically, overfishing has led to severe collapses in major stocks, such as the Atlanto-Scandian herring in the 1960s and the North Sea herring in the mid-1970s, demonstrating the profound impact of unsustainable harvesting. Even with current management, some areas like the Atlanto-Scandian region continue to experience overfishing, hindering recovery efforts. Additionally, bycatch—the unintentional capture of non-target species—poses a threat, as herring fisheries can inadvertently entangle marine mammals and seabirds. The practice of targeting spawning populations and older, more experienced fish can also diminish the stock’s reproductive capacity and disrupt the generational knowledge of migration routes and spawning grounds.
Habitat degradation also plays a substantial role in the vulnerability of herring. Dams and other man-made barriers obstruct river herring from accessing their ancestral freshwater spawning grounds, a factor that has historically and presently contributed to population declines. Pollution and contaminants in aquatic environments can harm herring eggs and larvae, impeding their development and survival. Coastal development, dredging, and activities like offshore oil and gas industries can also damage the specific benthic habitats where herring lay their sticky eggs, making these vulnerable areas susceptible to human disturbance. Eelgrass beds, for example, are a critical spawning habitat for Pacific herring, and their degradation directly impacts reproductive success.
Climate change introduces further complexities to herring survival. Rising ocean temperatures accelerate herring metabolic rates, potentially leading to higher mortality rates in larvae and juveniles. Warmer waters can also shift the composition of zooplankton, the primary food source for young herring, towards smaller, less nutritious species, and increase the abundance of predators that feed on herring. Ocean acidification, caused by increased absorption of carbon dioxide, negatively affects herring embryo development and metabolism, potentially resulting in shorter larvae and reduced survival rates. Changes in water flow and salinity also alter essential habitats, while warming seas can cause herring stocks to shift their distribution to cooler, deeper waters, impacting their traditional grounds and management strategies.
Herring’s Ecological Importance and Management Efforts
Herring occupy a foundational position in marine food webs, consuming plankton and efficiently transferring this energy to a wide array of larger marine life. These fish serve as a critical food source for numerous species, including large predatory fish like cod, salmon, tuna, and striped bass, as well as marine mammals such as seals and whales, and various seabirds. The sheer density of herring during spawning events creates a temporary feast for many predators, and their eggs themselves provide an important nutritional intake for coastal wildlife. Protecting herring populations is therefore essential for maintaining the health and stability of entire marine ecosystems.
Various management and conservation efforts are implemented globally and regionally to safeguard herring stocks. Fisheries management bodies establish annual catch limits and quotas based on scientific assessments of stock status to prevent overfishing. Regulations on fishing gear, such as restrictions on midwater trawling and specific mesh sizes for nets, are also in place to minimize impacts on herring populations and reduce bycatch. Spatial and temporal closures, including restrictions during spawning seasons or in sensitive nursery areas, further protect vulnerable herring life stages.
Beyond fishing regulations, habitat protection initiatives are underway. Dam removal projects, particularly for river herring, aim to restore access to historical freshwater spawning and nursery grounds, which has proven effective in increasing returns. Protecting critical spawning habitats from physical disturbance is also a priority. International cooperation is increasingly recognized as necessary for managing shared herring stocks that migrate across national boundaries. Continuous scientific monitoring, including stock assessments, biological sampling, and spawn surveys, provides the data needed for adaptive management and ensures that conservation efforts are informed by the latest scientific understanding.