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 pee 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 basins. 
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* 
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 
geysers and hot springs is entirely untenable for several reasons: 
First, 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 the Yellowstone National Park. By William C. Kendall. Bureau of Fisheries Document 
No. 818. 1915. 
3 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. x1, for 1891, 
0. 207-258, pl. XXXVI-XLU. 1893. 
