lO-FOOT TIDE LEVEL 



4-FOOT TIDE LEVEL 



12 

 NOON 



5 

 PM 



Figure 4. — Simultaneous temperature readings in the 

 gravel (8-10 inches deep) at various tide elevations in 

 Olsen Creek on a flooding tide cycle, August 30, 1961. 



temperature variations over 5 F. were 

 recorded at the 10-foot level. During low 

 waterflows in the creek, the gravel at the 

 10-foot-level thermometer probe was covered 

 by only a few inches of water and was subject 

 to warming by the sun. This is evident from 

 the temperatures taken on August 30 (fig. 4) 

 when a rise of 5° occurred at the 10-foot 

 level before the incoming tide had reached 



the 5-foot level. The creek water temperature 

 rose 1° at this time. 



The temperature did not usually fluctuate 

 as much at the 4-foot level as at the 3- and 

 5-foot levels. We believe this was caused 

 either by fresh-water seepage from a nearby 

 bog or by poor circulation through the gravel. 



Gravel composition . --Twenty-four gravel 

 samples were taken from the 3-foot through 

 the 11-foot tide levels with equipment similar 

 to that described by McNeil and Ahnell. ' The 

 core of the sampler excluded all streambed 

 nnaterials more than 4 inches in diameter. 

 Samples were washed through a series of 

 seven sieves with mesh sizes graduated from 

 50.8 to 1.0 mm. All material passing through 

 the smallest sieve was collected in a settling 

 funnel, and that portion settling out in 10 

 minutes •was nneasured by volume. The volume 

 of the materials left in each sieve and in the 

 settling funnel is expressed as percent of the 

 total volume for each sampling site (table 3), 



Not enough samples were obtained for a 

 connplete analysis of gravel sizes at different 

 tide levels, but they do show a decrease in 

 the amounts of the largest gravel size from 

 higher to lower levels and an increase of 

 materials snaaller than 1.0 mm. To define 

 more clearly the proportions of sand and silt, 

 a more extensive gravel sampling program 

 will be undertaken with smaller meshed 

 sieves. 



Fauna . --Intertidal inhabitants common to the 

 area were collected at low tides during July 

 and August 1961. Three habitats were san-ipled: 

 the main stream. Middle Slough, and the ex- 

 posed tideflat between. The distribution of 

 organisms by tide level is given in figure 5. 



' Measurement of gravel composition in salmon stream- 

 beds. Circular 120, Fisheries Research Institute, Uni- 

 versity of Washington, Seattle, 1960. On file at the 

 Bureau of Commercial Fisheries Biological Laboratory, 

 Auke Bay, Alaska. 



Table 3. — Mean percent by volume of stream bottom materials retained 

 by sieves and settling funnel 



