Fish Studies

​​​​ Adult salmon return from the ocean to spawn in freshwater streams. Depending on the salmon species, adults are usually between three and five years old when they return to reproduce. Once they spawn, they usually die within a week. The adult salmon carcasses play a crucial role in the aquatic food web by providing essential nutrients to the stream. These nutrients feed plants and macro invertebrates which in turn feed young fish in the spring. The City of Bellingham Natural Resources Division conducts spawner surveys in Squalicum, Whatcom, Padden, and Cemetery creeks. In fall and winter, spawning fish are monitored with walking surveys.

In spring, out-migrating juvenile fish are monitored using smolt traps. A "smolt" is one of the life stages of a juvenile salmon. This life stage occurs when the juvenile salmon begins its migration from freshwater to the estuary and adjusts to living in saltwater. Different Pacific salmon species spend different amounts of time rearing in freshwater. For example, Coho salmon spend one to two years rearing in freshwater after they emerge from the gravel as fry. They reach about 50-100 millimeters in size before they smolt and begin migration to the estuary. The timing of this movement correlates with spring freshets (high water flow from snow melt or spring rains).

Spawner Surveys

Spawner surveys are conducted to better understand how, when and where salmon use our streams. This information allows the City to be a good steward of the salmon habitat that weaves throughout Bellingham. When conducting a survey, surveyors walk upstream while recording the number and species of live and dead fish. Surveyors also record the location of redds (nests) and determine which species made the redd. The surveys are conducted once every 7-10 days through the spawning season (September – March). Surveys also assess potential blockages to fish passage.

Smolt Trap

 A smolt trap is a standardized method of quantifying how many fish are moving through a water system.  Smolt trapThe trap is designed to capture juvenile out-migrating fish during the spring. The trap is a stream-wide V-shaped corral that points downstream. The structure funnels fish into the vertex and box while allowing flow to continue downstream. The holding box is used so fish can be safely held onsite until they are identified and released. An upstream trap/pipe is installed to allow passage of spawning fish. The traps are checked multiple times daily, with fish species identified and counted.


Smolt traps have been located in Baker, Spring, Cemetery, and Squalicum Creeks.