162 



have in them but few species of fishes ; es- 

 pecially is this true of the upper Missouri, 

 and these are such species as we find in 

 the Black Hills. It is thus evident that 

 the fishes of this region migrated there, 

 and only such fishes as were able or will- 

 ing to live in the muddy, alkaline streams 

 of the great plains could have ever 

 reached the Black Hills. The minnows 

 and suckers are ever preyed upon by sun- 

 fishes, bass and the like, and to escape 

 them evidently sought retreat in the al- 

 kaline water, which was too much disUk- 

 ed by their enemies for them to follow. 

 Once there and accustomed to such water 

 they would migrate farther up stream un- 

 til they reached the clear, cool streams of 

 the Black Hills. If we compare the fishes 

 of two rivers whose mouths are near each 

 other,as the Ohio and the Missouri, those 

 fishes found near the mouths will be the 

 same species and the two river faunas 

 will differ most as you go toward their 

 sources. On the other hand, if you select 

 two rivers whose sources are near each 

 other, as the James and tributaries of the 

 Ohio, then the fish faunas will differ most 

 as you go towards their mouths. The 

 same is true of the Missouri and the Co- 

 lumbia. In such cases it often happens 

 that during high water some fishes are 

 able to pass from the head waters of one 

 river basin to the other, just as we see 

 the trout from the Columbia at the pres- 

 ent time colonizing the upper Yellow- 

 stone through the Two Ocean Pass. 

 Near the head waters of many mountain 

 streams there is usually a pass, which 

 ■contains a strip of meadow land where 

 the small streams from mountains unite, 

 forming the sources of two great rivers 

 flowing in opposite directions. This is 

 the case both at the Two Ocean Pass, 

 the source of the Missouri and the Co- 

 lumbia, and at the point where the Cana- 

 dian Pacific Railroad crosses the divide, 

 forming the source of the Frazier and 

 Saskatchewan rivers. 



Many mountain streams whose sources 



: are at present in no way connected may 

 have been so at no very remote period. 

 All of our streams which have their 



: sources within the glaciated area were no 

 doubt connected as the ice receded. The 

 drainage of Lake Champlain and the 



lakes in central New York was south- 

 ward at the close of the glacial epoch. It 

 is said that in times of high water one 

 may pass in a skifT from the head waters 

 of the Mississippi to the Red River of the 

 North. With such facts before us we can 

 easily understand why the fishes of two 

 rivers whose sources are near each other 

 should be most nearly alike nearest the 

 divide. If the two rivers were formed 

 about the same time, as no doubt were 

 the James and the Ohio, they would nat- 

 urally have several species in common. 

 In other words, the two fish faunas will 

 resemble each other throughout their 

 whole extent. In the case of the Mis- 

 souri and the Columbia, the former is 

 much the older stream, and while their 

 sources have fishes common to both 

 streams, in the lower parts of the rivers 

 the fish faunas are entirely different. The 

 upper Missouri river and its tributaries 

 are for the most part inhabited by Rocky 

 Mountain fishes, practically the same 

 fauna as we find in the Columbia, but few 

 species characteristic of the Mississippi 

 valley have been able to even cross' the 

 great plains and none have ever passed 

 the Rocky Mountain divide. 



In the study of the geographical distri- 

 bution of our fresh water fishes, we are 

 able to make a few generalizations as fol- 

 lows : Two rivers in the same latitude, 

 and belonging to the same great drainage 

 basin, and draining similar areas, will 

 have similar fish faunas. Thus we find a 

 great similarity in the fishes of the Wash- 

 ita and the Tennessee rivers, a much 

 greater similarity than we do in the fishes 

 of the Washita and the Cedar rivers. If 

 the stream is a large one, the fishes near 

 its source will be much unlike those near 

 its mouth. The fishes of Minnesota dif- 

 fer greatly from those of Louisiana, 

 though the drainage of these two States 

 is in the Mississippi river basin. Lime- 

 stone streams have in them more species 

 of fishes than do sandstone. All things 

 being equal, the larger of two or more 

 streams will contain the most species of 

 fishes. There are few, if any, rivers as 

 rich in species as the Mississippi river 

 and its tributaries. It drains one slope 

 of each of our two great mountain sys- 

 tems, besides an immense area of wood- 



