92 ANIMAL COMMUNITIES OF STREAMS 



conditions and being also positively rheotactic. The fish are able to 

 meet the current and to withstand the conditions of the stagnant pools. 

 The crayfishes live in the water in the spring and burrow in the 



35 



PIONEER STREAM FISHES 



FIG. 35. Black-nosed dace (Rhinichthys atronasus) (from Forbes and Richardson) . 



FIG. 36. Common sucker (Catostomus commersonii); length 18 in. (from Meek 

 and Hildebrand after Forbes and Richardson). 



FIG. 37. Blunt-nosed minnow (Pimephales notatus); length 2 to 3! in. (from 

 Forbes and Richardson). 



dry weather; adults of the aquatic insects creep into moist places 

 when the stream dries. Alice (53) has found that isopods are positively 

 rheotactic and that they can be acclimated to extreme conditions. 



