NORTHWESTERN LAKES OF THE UNITED STATES. 
109 
Lake Tahoe trout ( Salmo henshavn ) are reported to have been very plentiful in 
this lake, but since the outlet was dammed they have decreased, possibly due to the 
fact that they go over the dam to spawn and can not return. Mackinaw trout 
( Cristivomer namaycusJi) were introduced into several of the lakes in this section 
and are thriving especially well in Fallen Leaf Lake, where they offer excellent 
sport and are more plentiful than the Tahoe trout. 
The lake has relatively clear water, and the disk can be seen at 17 m. The 
temperature readings showed that the thermocline was between 15 and 20 m. The 
following crustacean forms were found in the limnetic catches: Diaptomus wash- 
ingtonensis, Cyclops viridis var. parcus, Daphnia pulex, and Bosmina longirostris. 
The Crustacea were most abundant above the thermocline. About 79.3 per 
cent of Diaptomus, 71.1 per cent of Cyclops, 31.8 per cent of Daphnia, and 77.8 
per cent of Bosmina were in the epilimnion. (See Table 12, p. 126, and fig. 20.) 
Forty-two per cent of the Daphnias were found between 15 and 20 m., or in the 
region of the thermocline. In the daytime Daphnia pulex was found in the region 
of the thermocline or just below it. A small number of Crustacea was found in all 
of the catches below the thermocline. 
The nauplii were most abundant in the 0-5 m. stratum of the lake. Fifty-two 
per cent were found in this layer and a few unevenly distributed below. 
The rotifers were most abundant above the thermocline, especially in the 10-15 
m. stratum. More than a quarter of the Anursea cochlearis and Notholca longispina 
and almost one-half of the Mastigocerca were found in this stratum. Anursea was 
found between 30 and 50 m. and also in very small numbers below 50 m. 
Ceratium was found only in the catches above 30 m., with the maximum 
number per cubic meter of water between the surface and 5 m. 
The chlorophyll-bearing portion of the plankton consisted chiefly of Asterionella. 
It was most abundant between 25 and 30 m. About 1,240,000 per cubic meter of 
water were found in this stratum. 
LAKE TAHOE, CALIF. 
Lake Tahoe, Calif., is probably the most widely known lake in western United 
States. It is noted for its picturesque mountain scenery, clear water, summer 
climate, and trout fishing. 
The lake lies on the Calif ornia-Nevada line, where the latter changes its direction 
from north and south to northwest-southeast. About two-thirds of the lake lies in 
California. Its greatest length is given as 36.2 km. (22.6 miles) and its width as 
20.9 km. (13 miles). It has an altitude of 1,897 m. (6,225 feet). Le Conte (1883, 
1884) found a depth of 501 m. (1,645 feet). We checked this result with the cali- 
brated sample line, although our error may have been a meter plus or minus. 
Soundings were made over a large part of the north end of the lake, but no deeper 
water was located, although quite an area, located two-thirds across from the 
Tahoe Tavern landing, had a depth of 500 m. For a further description of the lake 
and a list of literature see Notes on Lake Tahoe, its Trout and Trout Fishing, by 
Chancey Juday (1907). 
