4 U. S. BUREAU OF FISHERIES. 



the same time should discourage unnecessary destruction of fish life 

 and develop a spirit of cooperation with the Government agencies 

 that are striving to maintain the fish supply. 



The present report is a revised and amplified edition of the one 

 published by the Bureau of Fisheries in 1915. 2 The exhaustion of 

 the supply of that document and the continued public demand for 

 information on this subject, together with the availability of new 

 data on the fishes, make this publication desirable. 



INDIGENOUS FISHES. 



The native fish life of the park was profoundly affected by the great 

 lava flow which occurred over a large part of the park in Pliocene 

 times. Whatever fishes were then present were necessarily killed, 

 and, with the reestablishment of the watercourses after the cooling 

 of the surface of the lava, fishes in outside waters were to a great 

 extent prevented from reaching the lofty plateau, which comprises 

 most of the area of the park, by the high and steep falls over which 

 the streams leave the lava beds. 



It thus follows that the native fish fauna of the park is very limited. 

 Except in Yellowstone River and its tributaries practically no fishes 

 occur naturally above the falls, and in the extensive basin of that 

 river the few species that do exist gained access to the region above 

 the falls because of the imperfect watershed separating the Yellow- 

 stone and the Snake River Ibasins. 



The original comparative barrenness of the park in fish life was due 

 entirely to topographical conditions. The physical character of 

 the waters is, in general, highly favorable for fishes, and an examina- 

 tion of the streams and lakes of the park by Prof. Forbes in 1890 3 

 disclosed the presence in certain barren waters of an abundant in- 

 sect and crustacean food well suited for sustaining certain kinds of 

 fishes. The theory that would account for the original absence of 

 fishes in particular park waters as due to the high temperature and 

 chemical constituents of the great volumes of water flowing from the 



f^ysers and hot springs is entirely untenable for several reasons: 

 irst, native trout abound and flourish in various streams and lakes 

 in close proximity to the outpourings of geysers and hot springs, and, 

 secondly, both native and exotic trouts have been successfully planted 

 in barren waters receiving the discharge of geysers and hot springs. 



The fishes of natural occurrence in the park represent 10 species, 

 as follows: Longnose sucker, rosyside sucker, chub, silverside min- 

 now, longnose dace, dusky dace, Rocky Mountain whitefish, red- 

 throat trout, Montana grayling, and blob. Of these only the trout 

 and the grayling have generally been recognized as game fishes, 

 although the whitefish might properly be so considered. While these 

 were very abundant in certain waters, the annually increasing num- 

 bers of angler-tourists in the park made it desirable to augment the 

 natural supply of game fishes by the introduction into barren waters 

 of selected species of other game fishes. 



2 The fishes of tho Yellowstone National Park. By William C. Kendall. Bureau of Fisheries Document 

 No. 818. 1915. 



A preliminary report on the aquatic invertebrate fauna of the Yellowstone National Park, Wyo., and 

 the Flathead region of Montana. By S. A. Forbes. Bulletin U. S. Fish Commission, vol. xi. for 1891, 

 p. 207-258, pi. XXXvn-XJLU. 1893. 



