THE AQUATIC VERTEBRATES 1049 



fresh-water fishes. The first two groups are beyond the scope of 

 this chapter. 



The inland fishes, according to the physical character of the 

 environments selected by them, may be divided into the following 

 groups, in part suggested by Cope and Jordan. 



1. Lowland fishes: the bowfin, pirate perch, large-mouthed black 

 bass, sunfishes, mud-minnow, and some catfishes. 



2. Channel fishes, ranging from lowland to upland: the channel 

 catfish, the moon-eye, gar pike, buffalo fishes, and drum. 



3. Upland fishes: many of the darters, shiners, and suckers, and 

 the small-mouthed black bass. 



4. Mountain fishes: the brook trout, and many of the darters 

 and minnows. 



5. Lake fishes, inhabiting only waters which are deep, clear, 

 and cold: the various species of whitefish and the Great Lake 

 trout. 



6. Anadromous fishes, or those which run up from the sea to 

 spawn in the fresh water: the salmon, sturgeon, shad, and striped 

 bass. 



7. Catadromous fishes, that descend to the ocean to spawn: the 

 eel. 



8. Cave fishes, found exclusively in cave streams: the Ambly- 

 opsidae. 



Many of the species are found in more than one of the areas 

 mentioned. 



Inland waters vary greatly in the amount of the solids in solu- 

 tion or suspension. In the Great Salt Lake and the alkali lakes of 

 the west the amount of solids in solution is prohibitive to fish life. 

 In all other waters, however small, if accessible, fishes are found. 

 Even temporary ponds are colonized by catfishes and sunfishes if 

 they are at all accessible. Sediment is present in variable amounts 

 and some fishes, depending exclusively upon sight to detect their 

 prey, are found only in water free from sediment. 



Under given conditions in moving water, the amount of oxygen in 

 solution is tolerably constant. When a body of fresh water freezes 

 over, or after the summer thermocline is formed, the oxygen may 

 become reduced in quantity or disappear altogether in the deeper 



