Nearshore Habitat Use by Juvenile Chinook Salmon in Lentic ...

shallow to snorkel were surveyed through surface observations by walking slowly along
the stream bank. Because fish are often difficult to observe in riffles when using surface
observations, we used electrofishing equipment to sample this habitat in 2004. The
number of Chinook salmon and other fish were recorded for each habitat unit. At the
location of individual or groups of Chinook salmon, we also measured the water column
depth (surface to bottom). In 2003, surveys of Johns Creek were done once every 2
weeks from March to June while in 2004, surveys were conducted once every 3 weeks
from February to May.
Stomach samples of Chinook salmon from Johns Creek were also collected in
2003 to compare their diet to Chinook salmon collected from the lakeshore. Chinook
salmon in Johns Creek were collected with a small beach seine. Lakeshore fish were
collected at a site in the north end of Gene Coulon Park, approximately 1 km from the
mouth of Johns Creek. Stomach samples were taken once a month from the end of
February to the end of May. Fish processing, laboratory analysis, and data analyses for
stomach samples were done the same as tributary mouth sampling (see Chapter 5).
Culvert Creek. —In addition to Johns Creek, we also surveyed a small unnamed
creek or seep in Gene Coulon Park (Figure 27). It begins on the east side of the railroad
tracks about 100 m from Lake Washington. Except for a section under the railroad
tracks, the upper 35 m are daylighted. Sixty-five meters from the lake, the creek runs
through a small drain and drops 2.1 m into a culvert. The lower 65 m was available to
juvenile Chinook salmon and was located entirely in a culvert (Figure 32), thus we
referred to this creek as Culvert Creek. The outlet of the creek is along a riprap bank
(Figure 32). The creek has a small sandy delta. The delta has a steep gradient similar to
the riprap bank. In the summer and fall, the creek is usually dry. During the winter and
spring, base streamflows appear to be approximately 0.04 cfs.
Snorkel surveys were conducted along four transects at this location: 1) creek
(entirely inside culvert), 2) delta (4 m long by 3 m wide), 3) an adjacent 18-m-long riprap
shoreline and, 4) a 14-m-long gravel beach 40 m north of the creek’s mouth. The length
of the creek that we were able to snorkel varied with lake level. In February, the lake
level was low and the lower end of the culvert was perched above the lake level and the
creek was one long riffle. We assumed no Chinook salmon could use the creek during
this time period. As the lake rose, water was backed up in the culvert and we were able
to snorkel inside the culvert. Transects were surveyed four times, approximately once
every three weeks from March to May.
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