Located in the blocky lava on the west side of Wizard Island are situated three pools caused by the unequal flow of volcanic material. Their bottoms are below the surface of Crater Lake so that they are kept filled to the lake level by infiltration. During earlier times when the level of the lake was higher two of the pools were mere inlets.

The temperature of the pools varies 5 to 6 degrees F. warmer than that of the lake water. Green algae and diatoms cover the pool bottoms, and tend to give them a blue-green color when viewed from the Watchman.

The smaller of the pools is Cleetwood Pool, in which lies the remains of the Cleetwood, the boat used for the initial soundings of the lake in 1896. According to Ranger-Naturalist Wayne E. Kartchner in an unpublished report, there were two small rainbow trout located in this pool in 1936. They were again observed in 1937; only one was seen in 1938, and none in 1939. On August 2, 1939, six more fingerlings were planted. Observations this year revealed several fish were still to be found in this pool. They varied from eight to eleven inches.

Emerald Pool, the largest of the small lakes, contains so much aquatic vegetation that it has a definite emerald color, this pool is 150 feet long, 15 feet deep, and 35 feet wide. On visits August 17 and 23, many mayflies, stoneflies, water striders, salamanders, and tadpoles were observed; giving evidence of an abundance of fish food. Three large rainbows, one "as large as one's arm" were seen. Twelve trout were placed in this pool in 1939. At least three of them were taken by anglers in 1946.

The third pool, Rocky Pool, is located on the east side of a high ridge of blocky lava behind Emerald Pool. It is separated from the lake by higher lava barriers than the other pools, and is about 60 feet across. From the 1939 planting, it received six fish but on visits this year no trout were observed.

Two specimens were collected from Cleetwood Pool on August 11 by Ranger-Naturalist Water S. Vincent. Both were male rainbows. The stomach contents of these fish revealed that this pool contains a scarcity of fish food for conifer needles and vegetative matter, mainly diatoms, which have little nutritional value, made up the bulk of the contents.

Measurement of these fish and stomach contents are:

Specimen No. 470811-1 WI, rainbow, male, standard length: 21.3cm, total length: 24.1cm, weight: 158.3 grams. Stomach contents: 28 insect larvae, 12 shrimp, 750 Daphnia (water flies which are almost microscopic), 1 fragment of crayfish, and 50% vegetative matter (diatoms).

Specimen No. 470811-2 WI, rainbow, male, standard length: 20.2cm, total length: 22.9cm, weight: 126 grams. Stomach contents: 6 insect larvae, 1 terrestrial insect, 22 conifer needles (made up bulk of contents), 275 Daphnia, 10 shrimps, and 25% vegetative material.

This investigation shows that conditions within these pools are suitable for survival of trout.