Many people wonder what seatrout eat. The answer is simple: they love fish and crustaceans. Their diet changes with the seasons and where they live. They mostly eat small fish, shrimps, and crabs.
Sea trout are a special kind of brown trout. They live in the sea and move to rivers to spawn. They can grow up to 24 inches long and weigh a few pounds.
Sea trout can be found in many places. They live in the North Sea, the Baltic Sea, and even in New Zealand. They eat what they can find easily.
When they are in the sea, they turn silver with dark spots. In rivers, they look like regular brown trout. After they spawn, they go back to the sea to get ready for next year.
They mainly eat small fish and shrimps. This helps them get the energy they need. For more info, check out this article on sea trout diet.
Sea trout basics: anadromous brown trout diet in a nutshell
Sea trout are brown trout that go to salt water and then come back to spawn. They eat everything from river bugs to sea food, growing fast in brackish and coastal areas. Their diet includes small fish and crustaceans, changing with the season and location.
Sea trout feeding in the sea is based on what’s around them. They eat fish, small crabs, shrimps, prawns, and more. Knowing the tides and currents is key to catching them.
Sea-run form of Salmo trutta and why it matters for feeding
Going to sea opens up a new world of food. Sea-run trout eat herring, sprat, sand eels, smelts, shrimps, and small crabs. This diet helps them grow fast, more than river food can.
Many stay near coasts and fjords where food is easy to find. Others travel far when baitfish gather, always finding food.
From rivers to coasts: how migration shapes what they eat
Trout change their diet fast as they move from rivers to estuaries. They eat shrimps and young fish, then bigger prey as they reach beaches and points. In the Baltic and North Sea, small herring or sprat are a big part of their diet.
Studies in Denmark show they like coastal areas but sometimes go further for food. Their diet is based on what’s easy to find and full of energy.
Opportunistic predators across habitats
These fish are quick to adapt and hunt. They change what they eat based on wind, water, and light. This helps them grow well in different places.
Research in Scotland and the Baltic shows they eat many different things in a year. They grab sand eels or small crabs in the surf, always finding food efficiently.
Life stages and habitats that drive feeding behavior
Sea trout eat different things at different times and places. Their diet changes from freshwater to saltwater. Estuaries and fjords help them learn to eat in both worlds.
Juveniles in rivers: insect larvae and drifting invertebrates
Young trout live in rivers, eating nymphs and midges. They also eat mayflies, caddis larvae, and stoneflies. Ants and beetles that fall from trees are also on their menu.
When the water flows more, trout move to eat food that comes by. This helps them grow before they go to saltwater.
Smolts and kelts: energy needs before and after spawning
Smolts stop in brackish water to get ready for saltwater. They start drinking seawater and changing their bodies. They eat shrimps, small crabs, and baitfish after settling.
Before they spawn, trout eat less. But after, they eat a lot to get energy back. This helps them recover quickly.
Estuaries, fjords, nearshore reefs, and offshore forays
Estuaries help trout grow with food like amphipods and mysids. Weed beds are good places to hide. Fjords offer deep water and pelagic food when shoals come by.
On reefs, trout follow currents and light. Some stay close to home, while others go far to find food. This variety keeps their diet interesting.
| Stage/Habitat | Core Foods | Feeding Style | Why It Matters |
|---|---|---|---|
| Parr in rivers | Mayfly, caddis, stonefly larvae; drifting midges; terrestrial ants and beetles | Station-holding drift feeding | Builds skills and energy for the parr diet within the broader sea trout life stages diet |
| Brackish estuary | Grass shrimp, mysids, amphipods, small crabs, silversides | Edge cruising and ambush in colored water | Gentle salinity gradient supports smolt feeding and diverse estuary trout food |
| Nearshore reefs/weed beds | Sand eels, juvenile herring, gobies, polychaete worms | Current-oriented, low-light hunting | Structure concentrates prey; prime for kelt feeding early in recovery |
| Fjords | Sprat, small herring, krill analogs where present | Roaming with shoals over drop-offs | Fjord feeding habitat funnels pelagic prey and boosts growth |
| Offshore forays | Small pelagic fish and scattered invertebrates | Wide-ranging pursuit | Expands options when coastal prey thins; stabilizes the sea trout life stages diet |
What does seatrout eat
Sea trout eat a variety of foods in different places. They like small fish, shrimps, and worms. They also eat insects and mollusks. The size, season, and water type affect their choices.
Fish are a big part of their diet when they’re around. They eat herring, sprat, and sand eels. They also eat smelts and young eels.
Crustaceans like shrimps and krill are important too. They start feeding frenzies in the water. Amphipods, small crabs, worms, insects, and mollusks are also on the menu.
Studies show different foods in different places. In the Baltic, sprat and herring are common. In Norwegian fjords, small herring are a big part of their diet. Scottish sea lochs have a variety of prey species.
| Prey Category | Key Species | Habitat Context | Feeding Notes |
|---|---|---|---|
| Forage Fish | Clupea harengus, C. h. membras, Sprattus sprattus, Ammodytidae (e.g., Hyperoplus immaculatus), Atherina presbyter, Anguilla anguilla (glass eels) | Coastal shoals, fjords, estuary mouths | Size-selective strikes; bursts when schools are dense; drives rapid growth |
| Crustaceans | Shrimps, Meganyctiphanes norvegica, amphipods incl. Themisto spp., small crabs | Weed beds, brackish channels, pelagic layers | High availability near structure; fuels steady intake when fish are scarce |
| Worms & Insects | Polychaetes, aquatic and marine insects | Surf edges, river plumes, tidal flats | Picked during low-light or turbidity; complements fish-heavy bouts |
| Mollusks | Small bivalves and gastropods | Soft sediments, eelgrass beds | Occasional items; adds diversity to the sea trout food list |
| Regional Signals | Baltic sprat/herring; Norwegian small herring; Scottish mixed prey | Baltic Sea, fjords of Norway, sea lochs of Scotland | What do sea trout eat varies by density and season; coastal trout prey items shift quickly |
Sea trout eat different foods depending on the season and size. Knowing this helps us understand their diet. Their menu changes from fish to shrimps in a short time.
Fish prey: herring, sprat, sand eels, smelts, and more
Sea trout hunt fast, silvery fish when they slide off the tide line. They feed on different fish depending on where they are. Anglers often find the best fishing near schools of herring, sprat, and sand eels.
Studies in the Baltic and North Atlantic show why these fish are important. They explain why sea trout strike, miss, and sometimes catch a lot of fish.
Herring and sprat as key forage where abundant
F. Chrzan at the Sea Fisheries Institute in Gdynia found herring and sprat are key. They help sea trout grow fast. Anglers see this when herring and sprat are plentiful.
A study in Norwegian fjords also found sea trout eat a lot of small herring. This shows they are quick to eat when they can. Anglers can catch them near ports and piers when sprat are around.
Sand eels/sand lances: ubiquitous nearshore targets
Sand eels live on sandy bottoms near beaches and reefs. They are easy to find at first light. Sea trout eat a lot of them in a short time.
Start fishing on shallow bars and move a bit deeper as the sun rises. The same spot can be good again when the currents change.
Smelts and other small schooling fish
Smelts are another food source for sea trout. They are found in tight schools near kelp edges. Wind pushes them into these areas.
Sea trout also eat glass eels, which migrate through estuaries. This adds variety to their diet.
Seasonal availability and size-selective feeding
The size of bait fish changes with the seasons. Sea trout prefer certain sizes of fish. When there are many small fish, smaller lures work better.
Choose lures that match the size and movement of the bait fish. In summer, fish are wary, so use small, fast lures. In cooler weather, slow, small lures can imitate injured bait fish.
- Herring pushes offshore: track birds and rips; think slim metals and finescale flash for herring diet trout.
- Dense sprat clouds: small, fast retrieves that pulse; keep hooks fine for quick sets.
- Sand eel lines on bars: narrow, olive backs with pale bellies match sand eel forage in clear water.
- Smelt edges at dusk: subtle shimmer and stop-start moves cue smelt prey reactions.
By understanding these patterns, anglers can catch more fish. It’s all about matching the bait fish and the season.
Crustaceans, worms, insects, and mollusks in the mix
Sea-run brown trout don’t just chase fish. They also eat sea trout crustaceans in coastal areas. This is true in weed-rich shallows and estuaries. They eat what the water brings them.
Shrimps and krill analogs where present
When shrimp schools move along edges, trout show their pattern. Young and midsize trout eat grass shrimp and mysids. Bigger trout follow decapod pulses.
Offshore, trout meet Northern krill and pelagic amphipods. A Gulf study shows shrimp and copepods in catches. It gives a detailed look at what young trout eat.
Polychaete worms and marine insects near shore
On calm flats and tidal creeks, trout forage in a grid. They search silt and sand for worms. Wind and river plumes bring midges and beetles for quick snacks.
Small crabs and amphipods over weed beds
Eelgrass and rockweed beds are full of food. Amphipods and young crabs live there. Trout ambush them, and the tide brings more food.
Mollusks as occasional prey
Trout don’t mainly eat mollusks, but they do sometimes. They eat soft clams, small gastropods, or bivalve meats. They grab what they can and then move on.
- Key coastal forage: shrimp diet trout, amphipod prey, and small crabs over grass.
- Supplemental bites: polychaete worms trout and windblown insects in brackish seams.
- Occasional items: mollusk feeding trout when shells crack or siphons show.
Regional research insights: Baltic, Norway, Scotland
European coasts show big differences in what trout eat. In the Baltic, trout mainly eat schooling fish. Norway’s fjords have trout that eat fish found far out at sea.
In Scotland, trout eat a wide variety of food. This is because of the sheltered, rich waters of the sea lochs.
Baltic studies: dominant sprat and herring diets
Sea Fisheries Institute in Gdynia studied trout from 1959 to 1975. They found trout mostly ate sprat and herring. Young trout grew fast, but then grew slower as they got older.
Trout ate about 14 grams of food each day for every kilogram of their body. This shows how important food is for their growth in the Baltic.
Norwegian fjords: small herring driving high feeding intensity
A 2005 study in the Journal of Fish Biology found trout and Arctic charr mostly ate small herring. They even went as deep as 5,000 meters to find herring.
This shows that trout in Norway’s fjords eat a lot when herring are around. They get a lot of energy from these short, rich times.
Scottish sea lochs: 50+ prey species identified
Studying 1,277 stomachs in Scottish sea lochs found over 50 different foods. Trout ate fish, worms, and many other things. This shows how diverse the diet is in these waters.
A study in Animal Biotelemetry (Kristensen, Pedersen, Thygesen, Del Villar-Guerra, 2019) found something interesting. Trout in Denmark sometimes swim far from the coast. This is similar to what happens in other areas.
Freshwater vs. saltwater feeding shifts
River-born trout start simple. In streams, they eat aquatic insect larvae and small insects. This early phase shows how different their diet is from sea trout.
As they move to the coast, their diet changes. They start drinking seawater and their kidneys change. This transition can take days to weeks, and they eat less during this time.
Once in the surf, they eat more energy-rich foods. These include sprat, herring, and small crabs. Their diet changes, and they eat bigger meals less often.
Upstream, their appetite may decrease. But they don’t stop eating. Studies show that even mature sea trout eat in rivers. After spawning, they go back to the coast and eat marine prey again.
- Freshwater: insect larvae, drifting invertebrates, and seasonal terrestrial insects.
- Brackish estuaries: gradual acclimation; selective, cautious feeding during the shift.
- Coastal water: schooling fish and crustaceans drive rapid growth and body repair.
Migration and metabolism: why big meals matter
Long runs at sea need lots of fuel. When coastal prey is plentiful, big meals give sea trout a boost. This helps them change their bodies quickly and stay strong.
Rapid marine growth after sea entry
Sea trout grow fast in their first year. They can gain up to 24.5 times their weight. They eat oily prey like sprat and herring to keep up with their needs.
In the second year, they gain about 3.5 times their weight. By the third year, it’s about 2 times. As they get bigger, they eat in short bursts. This helps them build muscle and get ready for long migrations.
Energy rebuilding in kelts post-spawn
After spawning, kelts quickly return to the sea. They eat small herring, sprat, and sand eels to regain their strength. They need protein and lipids to rebuild their bodies and swim better.
Kelts eat often when bait is plentiful. They feed in short bursts to save energy. This helps them recover quickly.
Timing daily feeding with temperature and light
Feeding times change with the weather. In low light, baitfish swim close to shore. Sea trout catch them near weed lines and bars.
In warm or bright weather, fish go deeper. They return to the edges at dusk and dawn. This helps them find food efficiently.
When small herring flood Norwegian fjords, sea trout grow even faster. They mostly eat these herring. This helps them stay on track with their diet and growth.
Estuaries and fjords: nursery zones with diverse prey
Shallow inlets and long, protected channels are like starter kitchens for young sea-run brown trout. They find steady cover and a buffet that changes with the tide and season. The diet of these trout is varied, with quick bites near weed beds and short dashes along sandy seams.
Brackish food webs: shrimps, small crabs, and baitfish
Brackish prey trout eat grass shrimp, amphipods, and young crabs in the slack water behind eelgrass. When tides run, schools of smelts, young herring, and sand eels come close. This mix keeps fjord feeding trout busy at dawn and dusk, when baitfish swim close to shore.
Studies from Aarhus University and the Norwegian Institute for Nature Research show trout’s diet changes fast. They eat crustaceans and small pelagics quickly. This helps them grow fast after entering the sea and keeps their energy use steady in changing salinity.
Weed-rich shallows and camouflage hunting
In spring and early summer, many fish hide in knee-deep weed beds. They blend in with the surroundings, perfect for ambush. Their diet is slow but steady, with a crab plucked from a hole, a shrimp flicked off eelgrass, and a sudden turn to catch a sand eel.
When water warms, they go a bit deeper. At night, they return to the skin of the tide. Here, brackish prey trout line up along seams and catch passing prey.
Staying local versus ranging widely
Tagging programs around Denmark show many fish stay close to beaches and points. They favor fjord feeding trout that key on small herring waves and wind-blown bait. Some fish roam farther when there’s more food offshore, but most stay close and follow the tide.
Across these routes, coastal nursery habitats trout trade safety for food hour by hour. They go into channels at night, rest in lee pockets by day, and adjust their diet as baitfish pulses rise and fall with the weather and the moon.
Baitfish spotlights: sand eels and glass eels
When sea trout move into surf lines and estuary mouths, two prey types are key. Anglers should study baitfish profiles to stay ahead. Look for birds working, dim light, and current seams to know what’s on the menu.
Sand eel behavior and why trout key in on them
Sand eels are slim and bright. They hide in clean sand by day. At dusk and on moving tides, they move up and pulse along the beach.
This movement makes sea trout strike quickly. Stomach checks show many sand eels at once. This means trout feed in bursts.
Choose gear that matches their pencil shape. A narrow soft plastic or a slim metal spoon works well. These imitate sand eels in nearshore chop.
Glass eel migrations as seasonal opportunities
Every spring, glass eels move into rivers. They come from the Sargasso Sea. In brackish edges, they gather in outflows and culverts.
Trout feed on them in low light. The bite can start with a tide change or warm rain. Many classic flies match their thin, translucent body.
Keep your retrieve steady with small twitches. This mimics a wavering ribbon. When glass eels move, use subtle, pale tones and gentle speed.
Matching size, movement, and profile
Profile is key, color is secondary. If trout target 3–5 inch prey, downsize your lure. The Rapala Original Floater 11 cm is a favorite for its shape and roll.
- Size: choose lengths that match local forage; trim leaders for crisp action.
- Movement: quick pumps for sand eel sea trout; smooth glides for glass eel feeding trout.
- Profile: slim, bright bodies win in clear water; muted tones when light is flat.
Seasonality: how diet changes through the year
The sea trout diet changes with the seasons. In spring, smolts move to estuaries and eat a lot of shrimps and tiny fish. When sprat and herring appear, the trout grow fast.
In summer, trout prefer to hunt in low light. They look for small fish and crustaceans in the shallows at dawn, dusk, and night. On bright days, they hide in reefs and wait for food to come to them.
By late summer, trout move to river mouths. They keep eating coastal fish and crustaceans, like in Scotland and Scandinavia. This is when they eat a wide variety of prey.
When rivers call, trout go upstream to spawn. But some trout, like females, keep eating, even when they’re not supposed to. This was found by J. M. Elliott in 2005.
In winter, trout look for easy food. Post-spawn trout go back to sea and eat small herring and crustaceans. This helps them get ready for spring.
| Season | Primary Habitats | Typical Prey | Feeding Window | Notes |
|---|---|---|---|---|
| Spring | Estuaries, brackish edges | Shrimps, amphipods, juvenile sprat/herring | Daylight with tidal flow | Rapid early growth when pelagic schools arrive; anchors the seasonal sea trout diet. |
| Summer | Weed-lined shallows, reef drop-offs | Sand eels, small herring, sprat, smelts | Dawn/dusk/night | The summer feeding trout pattern shifts deeper under bright, calm skies. |
| Late Summer–Fall | Coastal staging zones, river mouths | Mixed baitfish, crabs, amphipods | Crepuscular peaks | Wide prey breadth in Scotland and Scandinavia; staging fish stil graze. |
| Spawning Period | Rivers and tributaries | Limited invertebrates, occasional minnows | Opportunistic | Spawning season diet shifts often curb intake; some females keep feeding (Elliott 2005). |
| Winter–Early Spring | Fjords, nearshore pelagic lanes | Small herring, shrimps, krill analogs | Daylight when prey concentrate | Winter prey trout behavior centers on rebuilding post-spawn condition. |
Angler takeaways: reading the menu to choose lures and flies
Start by seeing what fish are eating. In places like Baltic and Norwegian fjords, small herring or sprat are common. Choose slim, silvery lures that match these sizes.
Remember, bigger lures don’t always work. This is because fish prefer what they can eat. So, use a ruler to pick the right size for your lures and flies.
When sand eels are around, pick long, quiet lures. These work best when moved slowly over sand or near rocks. Many lures are made to look like sand eels because they work well.
In estuaries and weed beds, use different tactics. Go for shrimp, amphipod, or crab imitations in dull colors. These work best with short movements and pauses.
Try fishing during low light or cooler times. This is when fish are most active. In bright sun, fish deeper reefs and current seams. Use slower, deeper movements.
During glass eel runs, use small, dark lures near the surface. This is where fish are most likely to find them.
Season and condition matter too. Fish that are getting ready to spawn or have just spawned eat a lot. Then, they go back to eating what they usually do.
Scotland, Baltic, and Norway show that fish eat many different things. So, have a variety of lures and flies. This way, you can match what fish are eating and keep catching them.
