Eulachon - Thaleichthys pacificus  









Eulachon - Thaleichthys pacificus

General

Thaleichthys pacificus is a small anadromous smelt that spawns in the lower reaches of coastal streams and rivers between the Bering Sea and California. They resemble small Pacific salmon having a long and extended anal fin and an adipose fin.

There have been concerns that industrial pollution adversly affects runs from local tributaries. Log booms may affect eulachon larvae and juveniles in the headwaters of estuaries, however it has not been demonstrated. It is suspected that debris and anoxic water could accumulate. In rivers, change in volume and discharge patterns from forested areas are of primary concern which could change spawning habitat into non-utilized habitat. Entrainment of spawning eulachons has been documented during dredging projects in the Fraser River. Silt-induced smothering of eggs downstream of dredging operations is also a concern.

Common Names

A common english term is to call them candle fish because dried Eulachons burn like candles. Various First nations each have different names for eulachons.

Family

Osmeridae

Size

less than 25 cm

Geographic Range

The Columbia River has the worlds largest eulachon run.

In 2000, there were a total of 33 spawning rivers identified known in British Columbia (DFO, 2000).

> They are not found on any of the large coastal islands and are rarely found in the Strait of Georgia other than when they are returning to spawn. In large rivers like the Fraser, spawning occurs over a broad range of locations. Most runs are observed in tributaries, in which eulachons spawn, sometimes 50 - 100 km up a major river or canal

Reproduction

Almost all eulachon spawning rivers have spring freshets. Sediment loads and stream size are not factors. The duration of spawning is over a couple of days. Spawning occurs at mostly at night. Eulachons spawnin in the early spring. In the Columbia, they spawn in January and February. In the Fraser, they spawn in April and May. The Nass and Skeen begin in later February and early March.

Feeding

It is suspected that the stop feeding as they approach their spawning rivers.

Life History

Larval desities can be observed for a number of weeks. Juvenile eulachons will disperse to open marine waters within their first year and as early as within the first few months. Eulachons spend 2-3 years in near-benthic habitats in open marine waters between 20m and 150m (97% of their time in marine waters). During the pre-spawning stage, it is suspected they hold in brackish water as their bodies make adjustments to live in freshwater. This usually occurs between the end of summer the year prior to spawning.

Historic

It is during the pre-spawning phase that traditional fisheries gather eulachons for grease. Traditional knowledge is rich on spawning biology of eulachons including tidal and river flow conditions necessary.







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