Photo by: Sylvie Mazerolle

Eulachon, commonly known as Candlefish, are small anadromous fish that historically ran in large numbers throughout the Klamath River Basin.  They are relatively small fish (6-8 inches on average) of the smelt family whose lives are primarily spent in the ocean where they feed on plankton. Adults return to the rivers and creeks where their own lifecycles began to spawn and die. After their eggs have hatched, eulachon larvae are flushed from the river into the ocean. Eulachon, amongst other more commonly recognizable anadromous fish species, serve as an example of the interconnectedness of the Klamath River Basin and the Pacific Ocean. Their dwindling populations are another reminder of the importance of unobstructed rivers.

Historically, Indigenous populations throughout the Klamath River Basin and greater Pacific Northwest processed oil-rich, spawning female Eulachon into a “flavorful oil.” Due to the fat content of these small fish, the species earned the common name of Candlefish amongst settlers who utilized the dried fish as rustic (and likely odiferous!) candles. Eulachon oil was so valuable amongst Indigenous peoples that it was traded with far away tribes via so called “grease trails!”

The Klamath River’s ecological health, or lack thereof, is illustrated by the health of its anadromous fish spawning runs. The last notable Eulachon runs occurred in the late 1960s. Since then, their numbers in the Klamath River have steadily declined. This decline is a result of the installation of the Iron Gate and Copco hydroelectric dams on the upper reaches of the Klamath River and rising sea temperatures caused by climate change.

In decades past, Eulachon swam up the Klamath River in numbers large enough to support “popular recreational fisheries.” Rising sea temperatures over the last 50-100 years in conjunction with impacted spawning grounds have greatly reduced Eulachon numbers. Biologists believe that changes in the ocean’s temperature have impacted Eulachon food sources that historically sustained the fish on their return trip to spawn in Northern California rivers.

Eulachon’s position within the food web and their anadromous lifecycle makes the little fish a useful indicator species. Their population health and ability to reproduce are affected by numerous factors that can be studied to better understand the stability of specific species (i.e., animals preyed upon by Eulachon) and entire ecosystems (i.e., the health of the Klamath River Basin’s extensive and interconnected ecosystems). Studying Eulachon populations enables us to form a more well-rounded picture of the overall health and productivity of the ecosystems they inhabit.

Studying Eulachon populations has enabled the scientific community to form a more nuanced understanding of how one animal population’s health and productivity can reflect on the overall health of the ecosystems it inhabits. Unfortunately for Eulachon, the Klamath River Basin has become a difficult river ecosystem to traverse due to human intervention and ecological disruption. Hopefully, the removal of four dams on the Klamath River will increase Eulachon runs throughout the Klamath River Basin and the region’s communities will have renewed access to a once abundant fishery.