Forage Fish: Unsung Heroes of Healthy Ocean Food Webs

Forage fish are small schooling species that transfer energy from plankton to larger marine animals, including commercially valuable fish, seabirds, and marine mammals. Anchovies, sardines, herring, menhaden, sand lance, capelin, and sprat belong to this group. Although they are often less visible than tuna, salmon, or cod, their abundance and behavior help determine the condition of entire ocean food webs.

Essential Concepts

Forage fish eat plankton and are eaten by larger animals. Their schooling behavior concentrates food in accessible patches. Heavy fishing, warming water, habitat loss, and changing plankton supplies can reduce their ecological value. Protecting spawning areas and maintaining sufficient population levels helps support marine ecosystems and fisheries.

What Are Forage Fish?

“Forage fish” describes an ecological role rather than a single taxonomic family. These fish are generally small to medium-sized, live in schools, and feed largely on plankton. Some consume phytoplankton directly, while others eat zooplankton, including tiny crustaceans and larval animals.

Common examples include:

• Anchovies
• Sardines
• Atlantic and Pacific herring
• Menhaden
• Capelin
• Sand lance
• Sprat
• Silversides
• Small scad species

Many forage fish mature quickly and produce large numbers of eggs. These traits help populations recover from ordinary losses, but they do not make them immune to intense fishing or environmental change. Their numbers can fall rapidly because predators, fisheries, and climate conditions affect the same population at the same time.

Why Forage Fish Matter to Ocean Food Webs

Forage fish occupy an intermediate position in marine food webs. They convert the relatively small energy of plankton into fish tissue that larger animals can consume. In this sense, they act as biological links between microscopic organisms and predators at higher levels.

A single school may feed many species. Herring and sand lance, for example, can support cod, salmon, halibut, seabirds, seals, and whales. Menhaden provide food for striped bass, bluefish, weakfish, ospreys, and other predators along the Atlantic coast. In some regions, the seasonal arrival of forage fish determines where predators gather and reproduce.

Their importance extends beyond the number of fish present. Forage fish often form dense schools near the surface or along continental shelves. This behavior makes them available to predators that could not efficiently capture scattered plankton. A decline in school size or timing can therefore affect predators even before forage fish disappear entirely.

Forage Fish and Commercial Fisheries

People harvest forage fish for human food, bait, fishmeal, and fish oil. Sardines, anchovies, and herring are eaten directly in many countries. Menhaden are used mainly for bait and industrial products, while capelin and other species support regional fisheries.

Direct consumption can provide nutritious food with relatively low transfer loss through the food web. Fishmeal and fish oil also supply feed and nutrients to aquaculture and animal agriculture. Yet a harvest that appears sustainable from the target species’ perspective may still reduce food available to predators.

Fishery management therefore needs more than a calculation of how many forage fish can be removed while leaving a breeding population. Managers also need to ask how much prey predators require, whether the stock is concentrated in a small area, and whether several fisheries are drawing from the same population. Anglers can also learn how fish distribution affects success by reviewing the 90-10 fishing rule.

Major Threats

Forage fish face several connected pressures.

Overfishing can remove large portions of a population before predators have access to them. Because these species often gather in dense schools, fishing vessels can catch substantial quantities in a short period.

Climate change affects water temperature, currents, oxygen levels, and plankton production. A fish may remain within a region while its preferred prey shifts elsewhere. Warmer conditions can also alter spawning seasons and the survival of young fish.

Habitat change can damage spawning and nursery grounds. Coastal development, pollution, sedimentation, and altered river flow may affect shallow areas used by eggs and larvae.

Food-web disruption occurs when the loss of one species changes pressure on another. If forage fish decline, predators may switch prey. This can increase pressure on other small fish, crustaceans, or juvenile commercial species.

How Scientists and Managers Protect Them

Effective management often uses catch limits that account for predator needs, not only the target fishery. Seasonal closures can protect spawning periods, while area closures can preserve concentrated schools and nursery habitat. Monitoring programs track abundance, age structure, body condition, egg production, and predator diets. The National Wildlife Federation’s overview of forage fish also explains why these species are vital to marine ecosystems.

Scientists also use acoustic surveys, egg sampling, fisheries records, and seabird or marine mammal observations. Each method reveals a different part of the system. A strong assessment compares these sources instead of relying on a single survey.

Consumers can support better outcomes by choosing forage fish that are managed under credible science and by eating species such as sardines and anchovies directly rather than treating every small fish as industrial feed. Personal choices cannot replace public regulation, but they can affect demand.

Frequently Asked Questions

Are forage fish all small fish?

No. Most forage fish are small or medium-sized, but the category refers to their role as prey and plankton consumers. Some species grow larger during their life cycle while still serving as important food for predators.

Do forage fish eat other fish?

Some primarily eat plankton. Others consume fish larvae, small crustaceans, or juvenile organisms. Their diet changes with age, season, and local food supplies.

Why are sardines and anchovies important?

They provide food for larger fish, seabirds, and marine mammals, while also supporting human fisheries. Their schooling behavior makes them efficient prey and efficient targets for fishing fleets.

Can forage fish populations recover?

Yes, many recover quickly under favorable conditions because they mature early and produce many eggs. Recovery is less likely if fishing remains intense, spawning habitat is damaged, or ocean conditions continue to limit food and reproduction.

What is the main lesson about forage fish?

Their value cannot be measured only by their market price. A forage fish population also represents food for predators, energy moving through the ocean, and stability within the wider food web. Protecting that function requires precautionary harvest levels, habitat protection, and long-term monitoring.