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

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<strong>Ch<strong>in</strong>ook</strong> / m .<br />

5<br />

4<br />

3<br />

2<br />

1<br />

2003 - upstream reach<br />

2004 - upstream reach<br />

2003 - convergence pool<br />

2004 - convergence pool<br />

0<br />

2/1 Feb 3/2 Mar 4/1 Apr 5/1 May 5/31 Jun 6/30<br />

FIGURE 39.—Number of juvenile <strong>Ch<strong>in</strong>ook</strong> salmon <strong>in</strong> Johns Creek per stream length <strong>in</strong> the convergence pool and<br />

the stream reach immediately upstream of the convergence pool. The length of the convergence pool and upstream<br />

reach varied depend<strong>in</strong>g on lake level. The entire stream reach was 260 m. The upstream reach <strong>in</strong>cluded riffles,<br />

glides, and scour pools.<br />

Other salmonids <strong>in</strong> Johns Creek consisted primarily of sockeye salmon fry. Other<br />

fish observed <strong>in</strong> Johns Creek <strong>in</strong>cluded trout, prickly sculp<strong>in</strong>, coastrange sculp<strong>in</strong> (C.<br />

aleuticus), threesp<strong>in</strong>e stickleback, juvenile brown bullhead (Ameiurus nebulosus), juvenile<br />

suckers (Catostomus sp.), juvenile sunfish (Lepomis sp.), juvenile peamouth (Mylocheilus<br />

caur<strong>in</strong>us), and largemouth bass. <strong>Salmon</strong>ids and sculp<strong>in</strong>s were found throughout the <strong>in</strong>dex<br />

reach and throughout the study period; whereas, the other fish species were observed<br />

primarily <strong>in</strong> the convergence pool <strong>in</strong> May and June.<br />

In general, the diet of juvenile <strong>Ch<strong>in</strong>ook</strong> salmon <strong>in</strong> Johns Creek was similar to the diet<br />

from Lake Wash<strong>in</strong>gton. Chironomid pupae and adults had the highest %IRI on each sampl<strong>in</strong>g<br />

date <strong>in</strong> both Johns Creek and the lakeshore (Table 12). However, on two of the four dates<br />

(March 20 and April 22), the diet <strong>in</strong> Johns Creek was substantially different than the lake shore<br />

at north Gene Coulon Park (Table 12). In Johns Creek, chironomid pupae and adult made up<br />

less than 30% of the diet <strong>by</strong> weight on both dates, whereas they made up over 80% of the diet<br />

from the lake shore dur<strong>in</strong>g that time period. On March 20, oligochaetes were the most<br />

important prey item <strong>by</strong> weight and on April 22 other terrestrial <strong>in</strong>vertebrates (centipedes,<br />

isopods, and gastropods) made up over half of the diet <strong>by</strong> weight. The diet breadth <strong>in</strong>dex was<br />

also much higher for Johns Creek fish than the lakeshore fish on these two dates (Table 13).<br />

62

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