Beamer, E., Henderson R. and Wolf, K., 2010. Juvenile Salmon, Estuarine, and Freshwater Fish Utilization of Habitat Associated with the Fisher Slough Restoration Project, Washington 2009. Skagit River System Cooperative, La Conner, WA. pp. 66.

The Fisher Slough Restoration Project, located in the south fork Skagit River tidal delta
near the town of Conway, is intended to help recover the six populations of wild Chinook
salmon present within the Skagit River and its natal estuary. We report monitoring results
related to Phase 1 (of three), which replaces an existing tidegate with a new tidegate. The
goal of Phase 1 is to improve fish passage and tidal inundation to areas upstream of the
gate and protect adjacent farmland from flooding. Data collected in 2009, and reported in
this document, represent baseline values of fish utilization before tidegate replacement.
The old Fisher Slough tidegate, during the monitoring period of this report, was operated
in two ways: 1) neutral velocity and 2) cabled open. We estimated the upstream fish
passage opportunity for juvenile salmon at 49% of the time when the old tidegate worked
normally and 73% of the time when the doors were cabled open.
We found 17 different species of fish in the study area, including freshwater and
estuarine species, and six different salmonids. There were no differences in wild juvenile
Chinook salmon densities between upstream and downstream sampling sites. Differences
in wild Chinook salmon density occurred over the monitoring period, with highest
numbers in April and declining throughout the study period. However, juvenile Chinook
salmon were present in all months monitored (late February through mid-August). The
2009 results — pre-tidegate replacement — demonstrate that juvenile Chinook salmon
are moving upstream of the tidegate and that there are no significant differences in
abundance between upstream and downstream populations. The fish timing curves (e.g.,
presence and density) can serve to guide tidegate operation for better fish management.
We used selected environmental variables to improve understanding of the juvenile
Chinook salmon density trends independent of fish passage opportunity at the tidegate.
We concluded salinity, water depth, and water velocity are not likely influencing juvenile
Chinook monitoring results between sites up and downstream of the tidegate. We found
site differences in substrate and vegetation which may influence juvenile Chinook
monitoring results between sites up and downstream of tidegate. Dissolved oxygen levels
in Fisher Slough may be lower than ideal for juvenile salmon rearing and migration
requirements upstream of the tidegate during daytime in June or later in summer. Water
temperature is a factor contributing to juvenile Chinook salmon timing at the end of the
monitoring period (late July and August), but this factor is generally influencing sites up
and downstream of the tidegate equally.