Fish Biology and Limnology of Crater Lake, Oregon

of the mountain, into which the peak, without support, subsequently collapsed. The result of the collapse was an inverted cone, a volcanic caldera which in the years that followed filled with water to a depth of 1,996 feet. In most places the shores of Crater Lake rise as sheer cliffs 500-2,000 feet above the lake surface. Only one good trail leads from the rim to the lake edge. The angler or sightseer who wishes to reach the lake must descend this 1.5 mile trail which zigzags along the crater wall. Crater Lake has a surface area of 21 square miles. The elevation at the surface is 6,177 feet above sea level. Yearly precipitation is approximately 60-70 inches; consequently the lake level remains fairly constant. There is no inlet or outlet. The water is extremely soft. Van Winkle and Finkbinder (1913) gave the analysis of the water as 80 p.p.m. of solids; bicarbonates, sulphates, and chlorides were the dominant constituents. The unusual transparency of the water, in addition to its apparent blue color, is very attractive. Observations of the Secchi disk (like a white dinner plate) suspended below the surface on a cord show how remarkably transparent is the water. The disk was visible 36 meters (118 feet) below the surface on August 10, 1937; at 39 meters (128 feet) August 19, 1937; and at 40 meters (131 feet) August 27, 1937. Kemmerer, et al (1924) observed the disk at 27 meters (82 feet) September 5, 1913. A maximum summer surface temperature of 63.60F. (17.6C00.) was reco ded August 10, 1937. The minimum was 47'F. (8.3'C.) July 2, 1937.2 The last seasonal reading was 55'F. (12.70C.) September 3, 1937. Kemmerer et al recorded a surface temperature of 52?F. (11.10C.) August 1, 1913. Figure 1 shows that definite thermal stratification existed in the summer of