3 1 o Barriers to Dispersion of River Fishes 



the very crest of the great continental divide, to Two-Ocean 

 Pass; through this pass it may have a choice of two routes to 

 Atlantic Creek, in which the downstream journey is begun. Soon 

 it reaches the Yellowstone, down which it continues to Yel- 

 lowstone Lake, then through the lower Yellowstone out into 

 the turbid waters of the Missouri; for many hundred miles it 

 may continue down this mighty river before reaching the 

 Father of Waters, which will finally carry it to the Gulf of 

 Mexico a wonderful journey of nearly 6,000 miles, by far the 

 longest possible fresh-water journey in the world. 



"We found trout in Pacific Creek at every point where we 

 examined it. In Two-Ocean Pass we found trout in each of 

 the streams and in such positions as would have permitted 

 them to pass easily from one side of the divide to the other. 

 We also found trout in Atlantic Creek below the pass, and in 

 the upper Yellowstone they were abundant. Thus it is cer- 

 tain that there is no obstruction, even in dry weather, to pre- 

 vent the passage of trout from the Snake River to Yellowstone 

 Lake; it is quite evident that trout do pass over in this way; 

 and it is almost certain that Yellowstone Lake was stocked with 

 trout from the west via Two-Ocean Pass." EVERMANN. 



Mountain Chains. The Sierra Nevada constitutes also a 

 very important barrier to the diffusion of species. This is, 

 however, broken by the passage of the Columbia River, and 

 many species thus find their way across it. That the waters 

 to the west of it are not unfavorable for the growth of 

 Eastern fishes is shown by the fact of the rapid spread of the com- 

 mon Eastern catfish,* or horned pout, when transported from 

 the Schuylkill to the Sacramento. The catfish is now one of the 

 important food fishes of the San Francisco markets, and with 

 the Chinaman its patron, it has gone from California to Hawaii. 

 The Chinese catfish, described by Bleeker as Ameiurus can- 

 tonensis, was doubtless carried home by some Chinaman return- 

 ing from San Francisco. In like fashion the small-mouthed 

 black bass is now frequent in California streams, as is also the 

 blue-green sunfish, Apomotis cyanellus, introduced as food for 

 the bass. 



* Ameiurus nebulosus Le Sueur: Ameiurus catus Linnaeus. 



