problems of adjustment. The tows were made 

 at an approximate speed of 2.2 miles (3.6 

 kilometers) per hour and were ordinarily of 

 5 minutes duration." The 1957 oblique hauls 

 ranged from 2.0 to 2.5 miles per hour and 

 were from 4.5 to 5.5 minutes in duration. 



The Clarke- Bumpus meter was calibrated 

 by hauling itover a measured 122-foot (37. 2 m.) 

 distance six times and recording the revolu- 

 tions. Each revolutionof the meter represented 

 4.9 liters of water strained by the net. 



The literature contains many references 

 about the horizontal distribution of plankton 

 organisms and the choice of plankton sampling 

 sites on a lake (Ricker, 1938a and 1938b; 

 Rawson, 1953; Langford, 1953). Southern and 

 Gardiner (1926) observed large differences 

 in horizontal distribution of plankton organisms 

 between different stations on Lough Derg, 

 Ireland, which perhaps could be expected from 

 its irregular depth contours and the effect of 

 the large volume of water entering from the 

 River Shannon. Ricker (1938a) cites experi- 

 ments reported by Naber (1933) to the effect 

 that the mean number and variability of distri- 

 bution of various plankters in eight hauls 

 from different stations in the pelagic region 

 of the Lake of Plon, Germany, did not signifi- 

 cantly exceed the mean and variability in six 

 hauls from a single station. Ricker found that 

 choosing a central station to represent the 

 entire pelagic area of Cultus Lake, British 

 Columbia, was in general quite satisfactory, 

 although Cyclops, Daphnia, Bosmina, and 

 Notholca appeared to have a somewhat irregu- 

 lar rather than a random distribution. 



Because of the small size and rather uni- 

 form depth contours of Bare Lake, three 

 towing areas, one at each end and one in the 

 center, were established (fig. 2). They were 

 believed to be adequate to yield quantitative 

 and qualitative data from the metered hauls. 

 Samples were collected approximately every 

 tenth day from May 26 through September 4, 

 1957. All samples were preserved by adding 

 formalin until a 3- to 5-percent solution was 

 achieved. 



Almost without exception in plankton enu- 

 meration studies, only a fraction of a sample 



is counted. There are, however, several meth- 

 ods used in fractioning a sample. Ricker 

 (1938a) found by testing that the volumetric 

 methods of fractioning approached the ideal, 

 but that fractioning on a slide was not satis- 

 factory. He further observed (1938a, p. 31), 

 "As the collection itself is subject to a sampling 

 error of as great or greater magnitude, the 

 error of fractioning does not introduce addi- 

 tional uncertainty into a count of given size, 

 as long as the technique used is accurate, 

 i.e. purely random." 



The 1957 samples were all fractioned in the 

 following manner. Each metered sample was 

 increased in volume to a standard 100 ml, by 

 adding 5-percent formalin until the desired 

 volume was attained. Since plankton organisms 

 were far less abundant in Kemmerer samples, 

 each of these samples was standardized at 

 9 ml. Also, since the total sample consisted 

 of 9 liters of lake water, a 1-ml. fraction of 

 the 9-ml. concentrated sample would repre- 

 sent 1 liter of lake water. The samples were 

 then fractioned by (1) bubbling air through 

 the sample until the organisms appeared to 

 be thoroughly and evenly dispersed, (2) imme- 

 diately extracting 1 ml, of the sample with a 

 Stempel plankton pipette. The 1-ml. sample 

 was then transferred to a Sedgewick Rafter 

 Counting Cell, and the entire cell was counted. 

 Replicate counts were made of all samples 

 and where the observed variability warranted, 

 a third count was made. Approximately one- 

 third of the Kemmerer samples were counted 

 in total. Also, several samples were refrac- 

 tioned and counted by another worker. Kutkuhn 

 (1958) found that for macroplankton a high 

 degree of precision could be obtained from 

 one or two cell counts. 



The zooplankton species encountered were 

 tentatively identified in the laboratory, and 

 the identifications were later checked by 

 recognized workers in the respective fields. 

 The zooplankton population consisted of: 

 Keratella canadensis Berzins, Kerat ella 

 cochlearis (Gosse), Kellicottia longispinai^eWi- 

 cott),Ploesoma hudsoni (lmhoii),Conochilus 

 untcorrats (R O u S s e 1 e t), Asplanchna priodonta 

 (Gosse), Epischura nevadensis (L i 1 1 j e b O r g), 

 Bosmina coregoni (Baird), Bosmina longirostris 

 (Miiller), and Ceratium hirundinella (Miiller). 



