142 BULLETIN OF THE BUREAU OF FISHERIES. 



Breeding habits. — The Tahoe trout, or pogy, ascends the streams to spawn and 

 begins spawning, usually, about the middle of April. Mr. E. W. Hunt stated that 

 the trout began spawning about two weeks later than usual in 1904, and that they 

 averaged somewhat smaller in size than in former years. He also stated that the 

 average number of eggs obtained from each female was about 1,400. As late as August 

 a few trout may be found spawning in some of the streams, but generally the vast 

 majority are through by the middle of June. 



Some j'ears ago the California Fish Commission established two good hatcheries on 

 Lake Tahoe. Each hatchery has a capacity of about a million eggs, and almost every 

 season both are rilled to their utmost capacity with the eggs of the Tahoe trout. The 

 fry developed from these eggs are planted in Lake Tahoe itself and in the small lakes 

 tributary to it. Many of these small lakes did not possess trout until they were 

 stocked b} T the commission. The fry are usually planted about the first week in 

 August. The large increase in the catches of trout during the past two seasons is 

 undoubtedly due to two factors, first the activity of the California Fish Commission in 

 keeping the lake well stocked, and second, for the past four years the beginning of 

 the open season on June 1 instead of May 1 as formerly, so that the trout are now 

 protected during the most important part of their spawning season. 



The silver trout spawns in the lake, hence its eggs can not be obtained for the 

 hatcheries. 



Food. — Owing to the fact that the fishermen kept their trout alive several hours 

 after catching them, it was difficult to obtain good material for a study of the food. 

 As a result, out of a dozen stomachs of Tahoe trout that were examined, only three 

 were found to contain material of any consequence. The other nine contained only 

 small quantities of insect fragments that were too small to identify. Two stomachs 

 from trout that were 16 inches long were about one-fourth full. Each contained from 

 50 to 75 Daphnia and fragments of adult Chironomus and chironomid pupse. The 

 third stomach, from a male 15 inches long, contained 4.6 cubic centimeters of Daph- 

 nia, a small fragment of a beetle, and a few small fragments of other insects. The 

 number of individuals making up the 4.6 cubic centimeters of Daphnia was estimated. 

 Two separate measurements were made by allowing the material to settle for 24 hours 

 in graduated cylinders. In one case, 1.1 cubic centimeters contained 430 Daphnia, 

 and in the other, 1.3 cubic centimeters contained 477 individuals. The average for 

 these two measurements is 378 individuals per cubic centimeter, which multiplied by 

 4.6 gives a total of 1,739 Daphnia. This, however, does not represent the total 

 destruction of I><i/>lni i<i for this single meal, as the brood chambers of a large number 

 of them contained either eggs or embryos. About two-thirds of the. individuals were 

 Daphnia pulex and the rest were D. hyaUna. It is an interesting fact also that no 

 Copepoda were eaten, since both Epischura and Diaptomus were much more abundant 

 than Daphnia. The former are much more powerful swimmers than the latter, but 

 this fact alone is scarcely sufficient to account for their entire absence from the menu 

 of the trout. A difference in size does not answer the question, for Epischura «< va- 

 il, nsis is a large form and could be obtained as easily, apparently, so far as size is con- 

 cerned, as Daphnia. The three trout that had eaten Daphnia must have obtained 

 them at a depth of at least 40 feet, for these crustaceans were not found any nearer the 

 surface than this in the daytime on the feeding ground where these fish were caught. 



