Fish Active day and night

Eulachon

Thaleichthys pacificus

iNaturalist Wikipedia

The eulachon is the shimmering 'candlefish' of the Pacific, a tiny but mighty smelt that fuels an entire coastal ecosystem during its legendary spring migration.

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0 Habitats

Quick Identification

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Size

15 to 25 cm (6 to 10 inches) in length; 40 to 60 grams (1.4 to 2.1 ounces)

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Colors

Iridescent blue-green or silver-blue on the back with shimmering silver sides and a white belly; translucent fins.

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Key Features

Distinct adipose fin near the tail
Large pectoral fins reaching nearly to the pelvic fins
Oily, translucent appearance
Smells like fresh cucumbers when handled

When You’ll See Them

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Activity pattern Active day and night

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Peak hours Spawning peaks at night; predator activity peaks during daylight hours

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Season March-May

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Diet In the ocean, they filter-feed on krill, copepods, and other plankton. They cease feeding entirely once they enter freshwater rivers for spawning.

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Habitat Coastal marine waters and estuaries; moves into cold, gravel-bottomed freshwater rivers for spawning.

public Geographic range

Where Does the Eulachon Live?

Native to the North American Pacific Coast, the eulachon is found in the cold, nutrient-rich waters of the Eastern Pacific Ocean. Its core range extends from the Pribilof Islands in the Bering Sea down through the coastal regions of Alaska and British Columbia, reaching its southern limit in Northern California. They are specifically tied to large river systems like the Columbia, Fraser, and Nass rivers for their annual migrations.

Basemap © OpenStreetMap contributors

2 Countries

1.2M km² Range

Vulnerable Conservation

US United States CA Canada

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iNaturalist / Verified observation data

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Behavior

Eulachon, often called candlefish, are famous for their incredibly high lipid content, which can reach up to 15% of their total body weight. This oiliness is an evolutionary adaptation for their arduous anadromous journey, but it also made them a vital resource for Indigenous peoples, who dried the fish and used them as literal candles by threading a wick through their bodies. They spend most of their lives in the ocean and return to freshwater only to spawn.

During the spring, eulachon enter coastal rivers in massive, dense schools. This migration is a cornerstone event for the Pacific Northwest ecosystem, triggering a "feeding frenzy" that attracts thousands of bald eagles, seals, sea lions, and bears. They are highly social during this period, moving as a single shimmering mass to overwhelm predators through sheer numbers. Unlike salmon, they do not jump over obstacles and require relatively unobstructed river access.

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Camera Tips

Capturing the eulachon run requires specialized underwater equipment, as these fish do not break the surface like salmon. An action camera with an underwater housing, such as a GoPro, is the best tool for the job. Mount the camera on a weighted tripod or a heavy stone and place it in shallow, slow-moving side channels of a river where the gravel is fine. This is where the fish congregate to deposit eggs, providing the most stable footage.

Visibility is the primary hurdle in river environments. Aim to set your camera during periods of low turbidity—usually after a few days without heavy rain. Position the camera so it faces across the current rather than directly into it to prevent debris from sticking to the lens. If you are filming during the day, ensure the sun is behind the camera to highlight the brilliant silver iridescence of the fish's scales; at night, use a dim, diffused light to capture spawning behavior without washing out the scene.

For those without underwater gear, a trail camera can still capture the secondary action of the run. Set your camera on a high bank overlooking shallow riffles or gravel bars. Look for "bio-indicators" like massive flocks of gulls or congregating eagles. Use high-speed video settings to record the predators diving into the water. This provides a dramatic narrative of the eulachon's role as a keystone species even if the fish themselves remain mostly submerged.

Similar Species

Species that look similar or are commonly confused with Eulachon.

Surf Smelt

Surf smelt are smaller and spawn on saltwater beaches rather than migrating into freshwater rivers.

Longfin Smelt

Longfin smelt have noticeably longer pectoral fins and typically spawn earlier in the winter than eulachon.

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Frequently Asked Questions

Eulachon migration and spawning activity often peak under the cover of darkness at night to avoid visual predators, though they can be seen in massive schools during the day during the height of a run.

Since eulachon don't eat during their spawning run, you cannot use bait. If your property borders a coastal river, the best way to 'attract' them is to maintain a natural shoreline with overhanging vegetation and clean gravel beds.

In the ocean, they are planktivores, feeding on tiny krill and copepods. Once they reach freshwater to spawn, their digestive tracts shut down and they rely on stored body fats.

They are only found in suburban areas that sit along major coastal river systems in the Pacific Northwest, such as suburban reaches of the Fraser River in BC or the Cowlitz River in Washington.

Eulachon are generally larger than other smelt species and possess a distinct adipose fin. They also have a very characteristic cucumber-like smell when fresh, which is a key field identifier.

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