42 BULLETIN OF THE BUREAU OF FISHERIES. 



with that of others who would protect wild life and in a measure preserve the rivers and 

 forests from pollution and destruction. 



The mills, vnth a few exceptions, attempt to keep the water clear, but they are not 

 always careful to maintain a sufficient flow in the fishways. Small trout often pass out 

 into the irrigation ditches, where proper screens are lacking in the mains, and con- 

 siderable numbers of fishes are sometimes destroyed by the carelessness of those having 

 charge of the large dams." 



Complaint has been made against water birds — the pelicans, cormorants, gulls, 

 and terns — some of which have large breeding colonies on islands in the lakes. It is 

 apparent, however, that but little harm is done by these birds, except that they consume 

 food which might otherwise be available for the trout. 



In the upper courses of the desert streams the trout, and all other fishes as well, 

 are sometimes completely washed out or choked and killed as a result of sudden and 

 violent thunderstorms, known as "cloud bursts," when a great quantity of water is 

 precipitated on the mountain sides and, gathering force in the narrow gorges, sweeps 

 everything before it, not even the fishes being able to withstand the terrific rush. The 

 rise of a stream is sometimes so sudden that an advancing wall of water several feet in 

 height plunges along the river bed uprooting trees and battering down other obstacles 

 with rolling bowlders until at length it scatters everything pell-mell on the desert floor. 

 When streams connect with the main channel at only infrequent intervals, some time 

 usually intervenes between such a catastrophe and a natural restocking. Fortunately 

 such occurrences are not frequent. 



The possibilities of fish culture are relatively promising in this region, and con- 

 siderable responsibility rests with those in control of the situation. Moreover, several 

 species are threatened with extermination, and an attempt should be made to learn 

 something more of their habits before the fishes entirely disappear. 



SYSTEMATIC DISCUSSION OF SPECIES. 



Catostomus tahoensis Gill and Jordan. Red sucker. 



C. tahoensis is both fluvial and lacustrine and appears to be the most abundant sucker in the region 

 living and spawning wherever the water is of sufficient depth. * During the spring and early summer 

 its brilliant color, large size, and the commotion made by spawning individuals along the river bars, 



o During the spring of 1912 the local papers contained accounts of the destruction of large numbers of trout in the Tmckee 

 River below the irrigation dam at Derby. The writer visited the place at the time and carefully examined the river from the 

 town of Truckee to the mouth of the river. From the Derby dam and extending several miles down stream there were thousands 

 of dead trout ranging in length from 2 to 3 or more feet, their decaying bodies strewn along the bars and clogging the ripples. 

 The mortality was greatest within the first mile or two of the dam. There were hundreds of dead fishes above and below the 

 station of Derby, and some were seen as far down as the great bend. An examination showed that many of these had spawned, 

 while others had not. The cause of all this was evident beyond doubt. The river at the time was tmusually low, following a 

 winter of little rain and light snows in the mountains. At the very height of the spawning migration of the trout the impounding 

 dam at Tahoe City was closed, and the gates allowing the water to pass into the canal leading from above the dam near Derby were 

 opened, with the result that one could cross the lower Truckee dry shod. No trout could pass from the dam to Derby nor from 

 there to the big bend nor from the big bend to the lakes. Trout could not even survive in the deeper pools between Derby and 

 the dam because of their large numbers and the polluted water. 



^ It is worth while to note in this connection that C. microps, the fine-scaled sucker of the Sacramento, representative there 

 of this species, is rare, but few specimens having been taken. Also that C. rimicultis, the fine-scaled form of the Klamath, is 

 abundant in comparison with C. snyderi, which is rarely seen. It appears, then, that a fine-scaled form is able to thickly populate 

 the streams of one basin while just the reverse occurs in another. It also will be recalled that a coarse-scaled form, C. occ-identalis, 

 which is more abundant in the Sacramento, has extended its range to Eel River and neighboring streams as C. humboldiianus, in 

 which the scales are yet larger, and to the streams of Monterey Bay as C. mniotiltus, where the scales have also become larger. 

 No representative of C. microps, the rarer Sacramento form, is known from these streams. Likewise, it is C. rimictdus, the more 

 common form of the Klamath, but with fine scales, that has extended its range to the Rogue River. 



