Pacific salmon begin hunting for food almost as soon as they hatch. Their bodies change to move from freshwater lakes and streams as juveniles to the salty oceans. What the salmon eat changes as well.
Researchers carefully study the diet of migrating salmon. This helps people who run hatcheries, like the Cook Inlet Aquaculture Association (CIAA), figure out the best way to raise young salmon in hatcheries. It also gives commercial fisheries managers insight into why salmon runs are stronger in some years than others.
Salmon are anadromous fish, meaning they hatch in freshwater, migrate to the ocean to feed and grow, then return to rivers and lakes to spawn This incredible journey sees salmon transform from tiny fry to mighty adult fish.
A key part of this growth involves what salmon eat at each stage. Their diet provides energy and nutrients for survival and reproduction
In this article, we’ll focus specifically on the freshwater diet of young salmon. What exactly do these fish eat while living in rivers and streams before heading out to sea? Let’s find out!
Why Understanding Salmon Diets Matters
Knowing what salmon fry and juveniles feed on in rivers provides useful insights for:
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Salmon hatchery operations – Hatcheries can raise fry on appropriate feeds to support healthy growth.
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Fisheries management: The amount of natural food in a river affects how many young salmon make it to the next migration.
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Conservation efforts – Protecting key food sources helps sustain wild salmon populations.
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Anglers – Insights into salmon behavior and feeding patterns can aid fishing.
So let’s dive into the menu items of young river salmon!
Main Components of a Salmon Fry’s Diet
Salmon fry first feed after absorbing their egg yolk sacs. Their early freshwater diet consists mainly of:
Insects
Aquatic and terrestrial insects make up the bulk of a salmon fry’s diet. Some common insects eaten include:
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Mayflies – An important staple food. Fry gobble up mayfly nymphs.
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Stoneflies – Also called salmonflies. Both nymphs and adults are eaten.
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Caddisflies – Salmon fry consume larvae in their pebble cases.
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Blackflies and midges – Small swarming insects are easy targets for fry.
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Riffle beetles – Adults and larvae scraped from riverbed rocks.
Zooplankton
These tiny aquatic animals, including rotifers, copepods, and water fleas, are a key food source. Fry gulp down mouthfuls of zooplankton.
Amphipods
Also called scuds, these small freshwater shrimp-like crustaceans are a salmon fry delicacy.
Aquatic worms
Worms that fall into rivers are eagerly snatched up and eaten by salmon fry.
Fish eggs
Fry may opportunistically eat loose fish eggs from spawning salmon and other species.
How Fry Feed in Rivers
After absorbing nutrients from their egg yolk, newly emerged salmon fry need to start feeding very quickly to fuel fast growth.
They feed aggressively, darting around in shallow waters gulping down any small organisms their mouths can fit around.
Stoneflies, caddisflies and mayflies clinging to submerged rocks and vegetation make easy, abundant snacks. Zooplankton floating through the water column are sucked in.
Salmon fry feed most actively at dusk, dawn and night when insect activity is highest. During daylight hours, they hide under rocks and driftwood to avoid predators.
As they grow bigger, juvenile salmon start targeting larger prey like amphipods, worms and aquatic insect larvae. Small fish eggs and even very small fish fry may supplement their diet.
Growth Determines Migration Timing
A fry’s growth rate helps determine when it will smoltify and migrate to the ocean. Fast growth allows earlier migration, giving salmon a longer time to feed and grow at sea.
Abundant natural food sources in a river result in rapid growth. Hatcheries also optimize diets and conditions to speed up fry development.
Threats Can Reduce Food Supply
Salmon fry numbers in a river can be abundant, but food supply is finite. Limited food resources lead to high competition and mortality.
Any threats to the aquatic insects, plankton and other foods salmon fry rely on hinders survival:
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Pollution can degrade water quality and kill insects.
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Dams disrupt insect habitat and migration patterns.
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Climate change alters river temperatures, flow and food webs.
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Overfishing reduces adult spawners, limiting egg and larval food sources.
Protecting freshwater food webs is key to sustaining wild salmon populations.
Estuaries Offer New Menu Options
As salmon smolts prepare to enter the ocean, they may spend time feeding and adapting in the mixing zone of fresh and salt water called an estuary.
Here they sample a more diverse buffet including shrimp, marine worms, fish and crab larvae. This transitional diet readies them for the vast ocean feast to come.
Fry Grow Up Fast
A salmon fry’s first few months are a race against time to fuel rapid growth. Their freshwater diet provides the abundant nutrients they need before undergoing an incredible transformation at sea.
Understanding what salmon eat in rivers and how food drives growth gives us insights into better supporting our valuable salmon resources.
So the next time you see a feisty little salmon fry, think about the diverse watery world of food it needs to thrive into a powerful fish – and hopefully return one day to keep the life cycle going.
More Salmon Fun Facts:
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Salmon fry typically hatch at just 0.7 to 1.4 inches long.
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Fry can grow over 1.5 inches per month in optimal conditions.
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Most fry migrate to the ocean within 3-10 months after hatching.
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Outgrowing other food sources, some fry become cannibalistic, eating smaller fry.
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Salmon lose their urge to feed as they return to freshwater to spawn.
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Spawning salmon convert their food energy into eggs and milt.
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Each female salmon can produce 2,000 to 7,000 eggs.
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Only a small percentage of fry survive to adulthood.
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Salmon contribute nutrients from the ocean back to freshwater systems when they spawn and die.
The hatchery salmon diet
Salmon raised in CIAA hatcheries are fed fish feed from Bio-Oregon, a commercial supplier of fish food. This feed comes in different sizes and combinations of nutrients to follow salmon through their growth.
Hatchery food is made with fish meal, fish oil, and extra vitamins to make sure the fish stay healthy. This fish meal and oil can come from a number of places, such as food scraps from businesses that process fish for food. The rest of the feed comes from small fish that breed quickly in the ocean, like herring, sardines, and mackerel.
The salt water salmon diet
In the sea, salmon become predators, feeding on a wide variety of creatures. When salmon get out to sea, their main goal is to stay alive and eat a lot so they can get ready for their journey back to the spawning grounds.
At sea, salmon still eat zooplankton and crustaceans, which are similar to what they ate in fresh water. They also eat small squid, eel, and lots of shrimp.
In many ways, salmon become what they eat in the ocean. Consider the differences between coho, king, and sockeye fillets, particularly their color.
Carotenoids are a natural color found in many vegetables, like carrots, tomatoes, and pumpkins. They give salmon its pink or red color. Crustaceans such as shrimp and crabs contain high levels of carotenoids.
So it makes sense that crustaceans are the sockeye’s main food source, giving their flesh its unique red color. But coho and king salmon eat more than just crustaceans. They also like other small fish, which makes their meat more orange.
The Salmon’s Life Mission | Destination WILD
FAQ
What does salmon eat?
What fish do freshwater salmon eat?
Why do salmon go to rivers?
What is the best bait to catch salmon?
What do Atlantic salmon eat?
The diet of Atlantic salmon depends on their age. Young salmon eat insects, invertebrates, and plankton. The preferred diet of adult salmon is capelin. Capelin (similar in appearance to rainbow smelt) are elongated silvery fish that reach 8 to 10 inches in length.
What do salmon eat in the ocean?
When they’re in the ocean, young and adult salmon eat a wide variety of prey, including: Fish such as capelin, Atlantic herring, sand lance, barracudina and lanternfish. Crustaceans such as amphipods and euphausiids or “krill.”
Do Atlantic salmon eat saltwater?
Most Atlantic salmon follow an anadromous migration pattern, in that they undergo their greatest feeding and growth in saltwater; however, adults return to spawn in native freshwater streams where the eggs hatch and juveniles grow through several distinct stages. [citation needed] Atlantic salmon do not require saltwater.
Do salmon eat freshwater or saltwater?
Adult salmon typically spend most of their lives in saltwater habitats, where they feed on a variety of prey, including fish, squid, and crustaceans. However, they will return to freshwater habitats to spawn and lay their eggs. Overall, salmon are a vital part of both freshwater and saltwater ecosystems.