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

CHAPTER 8. LAKE QUINAULT SURVEYS
Introduction
Some habitat features such as LWD and emergent vegetation are difficult to study along
the highly developed shorelines of Lake Washington and Lake Sammamish because they are
rare. Outside of the Lake Washington basin, the only other major run of ocean-type Chinook
salmon that spawn above a large lake in the State of Washington occurs in the Quinault River
above Lake Quinault. In 2003, we conducted a preliminary investigation of Lake Quinault to
determine if the lake could be used to study the habitat features that are rare in the Lake
Washington basin. A few day and night snorkel surveys were conducted in April and July.
Large numbers of Chinook salmon were found along the lake shoreline and the lake had large
areas with LWD and emergent vegetation. Additionally, the shoreline is relatively undeveloped
and the only introduced fish species is common carp, which do not appear to be abundant.
Therefore, the lake appeared to be an excellent site to study juvenile Chinook salmon habitat use
in a pristine lentic environment and examine some habitat features not found in the Lake
Washington basin.
Methods
Chinook salmon habitat use was studied during two periods in 2004; one in late April and
another in late June. The nearshore area was divided in one of five habitat types (Figure 44):
open beach (gentle slope) with small substrate (sand and gravel), bedrock and large substrate
(steep slope), emergent vegetation (Figure 45), LWD (Figure 45), or tributary mouths. Except
for deltas of some small tributaries, we only used nearshore areas where the shoreline habitat was
the same for at least 50 m.
The maximum transect length was 120 m. Only one area of the lake had bedrock and
three transects were established at this location (Figure 44). These transects were surveyed on
each study period during both day and night. Seven tributary mouths were chosen, three (Gatton
Creek, Falls Creek, and Willaby Creek) are spawning streams for Chinook salmon, the other four
tributaries are considered nonnatal streams. For the other three habitat types, we used a stratified
random sampling design to select transects to survey. Sampling consisted of both day and night
snorkel surveys. We tried to survey the same transects on each study period during both day and
night; however, we were not able to survey a few transects due to time constraints or weather
issues. On low to moderate sloping shorelines, two depth contours (0.4- and 0.7-m depth) were
surveyed, while on steep sloping shorelines only one depth contour (0.4- m depth) was surveyed.
Chinook salmon (separated into those greater than and less than 60 mm FL) and other fish were
counted along each transect. A habitat survey was also done at each transect. Information
collected included: substrate type, length, slope, and amount of structure (woody debris or
emergent vegetation).
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