plankton production. Plankton production in 

 Ruth Lake increased innmediately after the 

 rotenone treatment, and this level remained 

 high through 1964. A quantitative and qualita- 

 tive study was started in 1962 to evaluate 

 more effectively the plankton productivity of 

 the various lakes in the area. Samples from 

 Ruth and Little Kitoi Lakes were taken within 



1 day of each other in 1962 under similar 

 conditions. Each sannple was collected by 

 towing a 12-in. net of 20-mesh silk bolting 

 cloth a distance of 100 ni. at a depth of 6 m. 

 The settled volume of plankton in the Ruth 

 Lake sample was 22 ml, (milliliter), whereas 

 in the Little Kitoi Lake sample it was only 



2 ml. Samples from Ruth Lake consisted pri- 

 marily of cladocerans, whereas those from 

 Little Kitoi Lake contained mostly rotifers. 

 It is impossible to state exactly the cause for 

 the shift of Ruth Lake to a higher level of 

 plankton productivity. Both release of fertility 

 by the destruction of resident fishes and reduc- 

 tion in the numbers of plankton-eating fish 

 must have played a part. 



Stomachs of most smolts from Little Kitoi 

 and Ruth Lakes, taken within a few hours after 

 the fish had left the lake, were empty. When 

 they contained food, nnidge larvae (Tendipedi- 

 dae) were the primary organisms in both 

 lakes, although oligochaete wornns were also 

 an important food in samples from Ruth Lake. 

 Several of the stomachs of fish from each 

 lake contained a small amount of partly di- 

 gested plankton. Nonmigratory juveniles were 

 not sampled for stomach contents because 

 sufficient numbers of fish were hard to get; 

 samples fronn these fish would certainly be 

 better than those from the migrating smolts 

 to indicate feeding habits in the two lakes. 



Because of the diversity of substrate for 

 collecting periphyton each year (see 

 "Methods"), presentation of the original data 

 would not be useful. The relative conditions 



in the three lakes can be brought out, how- 

 ever, by comparing the accumulation in the 

 three lakes with the amount accumulated per 

 unit area in Ruth Lake (table 13). The com- 

 parisons showed Ruth Lake to be the more 

 productive- -usually by a wide margin. 



The greater productivity of Ruth Lake is 

 shown further in a comparison of bottom fauna 

 there and in Little Kitoi Lake (table 14). The 

 weight of bottom organisms per square meter 

 in the shallow water of Little Kitoi Lake 

 (0.624 g.) was only 38.9 percent of that 

 in Ruth Lake (1.604 g.). In deep water, Little 

 Kitoi Lake had 2.433 g. of organisms per 

 square meter, or 44.5 percent of that in Ruth 

 Lake (5,469 g.). Larvae of Tendipedidae from 

 Ruth Lake were considerably larger than were 

 those from Little Kitoi Lake; as a result the 

 bottom-fauna biomass from Ruth Lake was 

 greater than from Little Kitoi Lake, although 

 the number of organisms per square meter was 

 sometimes higher in Little Kitoi Lake than in 

 Ruth Lake. 



Table 13, — Accumulation of periphyton in 

 Little Kitoi, Ruth, and Mldarm Lakes ex- 

 pressed as percentages of the amount accumu- 

 lated per unit area in Ruth Lake 



^ No data for 1957. 



Table 14-, — Average number and wet weight of bottom organisms per square meter in 

 Little Kitoi Lake on 6 days between March 6 and September 18, 1961, and in 

 Ruth Lake on 5 days between March 6 and September 19, 1961 



■"■ The major groups in this category were gastropods ( Gyraulus sp.), pelecypods 

 (Sphaeriidae ), and amphipods ( ityalella sp., Gammarus sp.). 

 ^ No sample taken on March 6. 



16 



