Protozoa formed a small and variable por- 

 tion of the total plankton, reaching maximum 

 abundance of 17,000 individuals per liter on 

 August 23 at the 5-meter depth at station 11. 



The total plankton of Brooks Lake in 1957 

 was generally abundant throughout the season 

 and well distributed to all depths. 



MORPHOMETRY 



The bottom morphometry of Brooks Lake 

 had to be determined before we could make 

 a map on which we could base planning of 

 future biological and chemical sampling pro- 

 grams. A Raytheon portable recording echo 

 sounder model DE 119B, which could be read 

 to within half a foot over a range of to 245 

 feet, was used, A hand-sounding line was used 

 to calibrate the sounder and to sound the areas 

 beyond maximum range of the instrument. 



A bracket consisting of a 1/4-inch bolt 

 through the left gunwale, with the outer end 

 embedded in a small wooden fairing block, 

 was used to mount the transducer rod on the 

 boat. The transducer rod was clamped to the 

 outside of this block so that it pivoted on this 

 point (fig. 32). The upper projecting end of the 

 transducer rod was guyed in place by two 

 stout lengths of twine secured to the gunwale 

 fore and aft. When not in use the transducer 

 rod was pivoted so that its axis lay along the 

 gunwale. 



Sounding techniques and construction of the 

 map followed the methods described by Warner 

 (1953). Fifty-seven sounding transects were 

 made across Brooks Lake (fig. 33). Based on 

 these transects, a large-scale master map was 

 drawn with contour intervals of 10 feet, which 

 are increased to 40-foot intervals in figure 

 34 for clarity. 



The surface area of the lake is 28.9 

 square miles, excluding the islands. Maximum 

 length is 10.7 miles and maximum width, 4.1 

 miles. Mean width is 2.7 miles. Maximum 

 depth is 258 feet at the point indicated on 

 figure 34, and mean depth is 148 feet. Length 

 of shoreline is 31.5 miles and shoreline 

 development, 1.7. The volume is 2,745,600 



acre feet. The surface altitude is 62 feet 

 above sea level. 



BOTTOM FAUNA 



A limited number of samples were taken 

 with an Ekman dredge at stations I, II, and 111 

 (fig. 21) to learn the general composition and 

 distribution of bottom fauna. In general, bottom 

 fauna (mainly Diptera larvae) was abundant 

 at station I (5 m.) but decreased to almost 

 none at station III (67 m.). Our studies of 

 sockeye salmon food indicate that bottom fauna 

 is not directly important to sockeye salmon. 

 This finding agrees with the Cultus Lake 

 studies of Ricker (1952). 



WATER QUALITY 



Temperatures and chemical qualities of 

 Brooks Lake water were determined at sta- 

 tions I, II, and III, which were selected as 

 representative of the shallow-, medium-, and 

 maximum-depth areas of the lake. Samples 

 at each station were taken at 10-day intervals 

 between July 4 and September 3. The water 

 qualities chosen for measurement were those 

 believed to be most likely to be limiting 

 factors or to affect production of sockeye 

 salmon. Samples were collected with a 3-liter 

 Kemmerer water sampler, transferred im- 

 mediately to brown, ground-glass stoppered 

 bottles and were analyzed within 30 hours. 

 Samples kept overnight before being analyzed 

 were kept cool by storing in a refrigerator. 

 Glassware was scrupulously cleaned with de- 

 tergent and rinsed with distilled water imme- 

 diately before use. 



To insure use of identical techniques for 

 comparative purposes in future years, a de- 

 tailed description of each analytical technique 

 was prepared. Pertinent data were recorded 

 at the time a sample was taken. 



Temperatvire 



Water temperature is of vital importance 

 to the entire biota of a lake and is one of the 

 principal factors in determining overall pro- 

 duction. 



49 



