EXPLORATIONS IN COLORADO AND UTAH. 
5 
uot IVotn one to ten times liowed ov^er some field, while the beds of many considerable 
streams (Kio la Jara, Rio Alamosa, etc.) are filled with dry clay and dust. 
Great numbers of trout, in many cases thousands of them, pass into these irrigat- 
ing ditches and are left to perish in the fields. The destruction of trout by this agency 
is far greater than that due to all others combined, and it is going on in almost every 
irrigating ditch in Colorado. 
It is uot easy to suggest a remedy for it. The valleys in question would be worth- 
less for agriculture were it uot for irrigation, and the economic value of the trout 
is but a trifle as compared with the value of the water i)rivileges. It is apparently 
impossible to shut out the trout from the ditches by any system of screens. Ttiese 
screens soon become clogged by silt, dead leaves, and sage brush, and thus will not 
admit the passage of the water. 
Perhaps most of the trout are lost by entering the ditches in the fall, when run- 
ning down stream with the cooling of the water. It has been suggested that a law 
could compel the closing of the ditches after the harvest, allowing the streams to flow 
freely until March or April. In the fall the water is worth most to the fishes and 
least to the farmers. I am unable to say whether this jdau will jirove practicable or 
effective. This is certain, that if the present conditions go on the trout in the lower 
courses of all the streams will be exterminated, and there will be trout only in the 
mountain lakes and in the mountain meadows, to which agriculture can not extend. 
INDIGENIOUS FISHES. 
The fishes of Colorado are very few in number, notwithstanding the fact that four 
distinct faunal basins are within the limits of the State. 
The trout, Salmo mylnss Walbanm, and its varieties are found in all the mountain 
lakes and streams, down to a point where the summer temperature reaches GtP to 65°, 
when they gradually disappear. In clear streams and streams with bottoms of gravel 
they extend much farther than in turbid streams or those with clay bottoms. 
The mountain minnows, Bhinichthys dulcis, on the eastern slope and in the Rio 
Grande, and Ayosiayarroivi, in the Colorado basin, accompany the trout in the mount- 
ain meadows, not, however, ascending so near to the sources of the stream. On the 
other hand, they extend their range farther down than the trout, and exist in millions 
in the upper part of some of the valleys. They seem to be harmless little fishes, and 
they are eaten by the trout. 
The blo,b or Miller’s Thumb {Coitus hairdi punctulatus) is equally fond of cold 
and clear waters. In the Colorado basin it is very abundant, but in the other regions 
it is scarce, if present, and we did not find it. It is very destructive to the eggs of 
trout. 
The suckers of various species extend up the rivers more or less to the point 
where the trout disappear. Generally speaking, the suckers of the different basins 
are uidike. We found ymejts and Catostomus teres m tho, Platte, the for- 
mer ascending the streams much higher than the latter. In the Arkansas, Catostomus 
teres; in the Rio Fantosteus pleheius ; in the Colorado, Fantosteus delpliinus, 
Catostomus latipinnis, and Xyrauchen cypho. The species of Catostomus and Xyrauclien 
reach a considerable size, and are food-fishes of poor quality. All are destructive to 
the eggs of the trout.' 
