FISHERY BULLETIN: VOL. 71, NO. 3 



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 1961 1962 



Figure 2. — Maximum-minimum temperatures at 0.8 m 

 (2.5 feet) taken with reversing thermometer at station 2, 

 1961-62. 



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9/ 30/61 2/3/62 



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4 6 8 6 B 10 12 14 16 le 20 22 24 8 10 12 M 2 4 



TEMPERATUHE CO 

 • BOTTOM 



Figure 3. — Representative temperature profiles for station 

 1 on 3 April, 21 July, and 30 September 1961 and 3 Feb- 

 ruary 1962. Changes in depth were caused by irrigation 

 drawdown. 



gen were usually absent in the nearly stable 

 water mass below 4.3 m (e.g., the 8 August 

 1961 profile in Figure 4). Upward from this 

 depth, concentrations increased to maxima of 

 6 to 13 mg/liter, depending upon algal activity. 

 After fall turnover and the second irrigation 

 drawdown (in late September), dissolved oxygen 

 concentrations exceeded 6 mg/liter at all depths, 

 even during periods of ice cover, until the fol- 

 lowing spring (Figure 4, profiles for 30 Sep- 

 tember and 9 December 1961). 



Chemical analyses of water indicated a high 

 basic fertility for the reservoir. Total dissolved 

 solids generally exceeded 80 ppm and occasion- 

 ally were as high as 220 ppm on the bottom; 

 and early-to midsummer volatile dissolved solids 

 mostly varied between 80 and 100 ppm (Figure 

 5). Total phosphorus concentrations exceeded 



2 4 6 



024680246 



DISSOLVED OXYGEN (mg/l) 



Figure 4. — Representative dissolved oxygen profiles for 

 station 1 on 6 May, 8 August, 30 September, and 9 De- 

 cember 1961. 



0.4 ppm at the bottom and 0.2 ppm at the sur- 

 face (Figure 5). Surface pH (Figure 6) rose to 

 10.0 during algal blooms, although it generally 

 varied between 7.0 and 8.5 for all depths. 

 Methyl orange alkalinity usually exceeded 60 

 ppm and approached 130 ppm expressed as 

 CaCOa (Figure 7). 



The reservoir supported high summer den- 

 sities of plant and animal life. Sago pond weed, 

 Potomogetoii pecti}iatus L., choked the inlet 

 until water drawdown stranded the plants. 

 Much less rooted aquatic vegetation grew out- 

 side the inlet area because of limited shallow 

 water. Blue-green algae of the genera Aphaiii- 

 zome)io)i and Microcystis dominated the phyto- 

 plankton and gave a characteristic copper-blue 

 stain to the shoreline. Cladocera and lesser 

 numbers of other Entomostraca composed the 

 bulk of the zooplankton and were noted to be 

 abundant at various times of the year. Native 

 rainbow trout were kept at low numbers by the 

 chemical treatment (made several months be- 

 fore fry were introduced) and by subsequent 

 gillnetting. The littoral zone was well populated 

 with larvae of Ephemeroptera, Odonata (mostly 

 Coenagrionidae), Trichoptera, and Diptera 

 (Chironomidae). Amphipods (Gammaridae) 

 were numerous, and some crayfish (Pacifasticus) 

 and snails (Physa) were observed. The deeper 

 benthic zones were inhabited primarily by 

 oligochaetes and by Chiro)io)ni(s and Chaoborus 

 larvae. At times during the summer, large 



880 



