FAMILY SALMONIDAE 109 



Figure 12. Coast rainbow trout. Salmo gairdnerii irideus. male. 18 inches long. 



scales are rather large and number 120-140 in the lateral line. The tail 

 fin is slightly forked. The dorsal fin contains 11 rays, the anal fin 10-12 

 rays. 



This fish is native to the streams of the Pacific Coast, the steelhead 

 variety being a seagoing type. Ichthyologists now agree that the steel- 

 head and rainbow trouts are the same species, at least so far as those 

 introduced into this region are concerned. Hubbs (1926) aptly stated 

 that the variation is due entirely to conditions of water and develop- 

 ment. 



Early introductions of the Shasta rainbow trout, S. gairdnerii stonei, 

 were made in Wisconsin, Minnesota, and other northern states. Later 

 steelhead rainbow trout were successfully introduced into many waters 

 of Minnesota and neighboring states and have now largely replaced 

 the earlier planting. They are thriving in Lake Superior as a result of 

 the stocking of tributary streams, which the trout are unable to reascend 

 once they have reached the lake. In spring they run into the mouths of 

 all the rivers to spawn. A few years ago one weighing 15 pounds was 

 taken a short distance up the Knife River in Minnesota, and many 

 others of nearly this size have been taken near Grand Marais. Casting 

 and trolling alongshore in Lake Superior for this species as well as for 

 brook and brown trout have increased in recent years. Some of the 

 smaller interior lakes have responded quickly to plants of this fish, but 

 efforts to maintain them in streams have too often ended in failure. 

 The greatest success has been achieved by the introduction of a south- 

 ern strain of this species into Minnesota waters. Most rainbow trout 

 spawn in the spring, but this strain, for which the original stock was 

 obtained from Missouri, spawns from the last part of October until 

 early in February. Until the drought (1932) struck southern Minne- 

 sota, the strain was taking splendidly in several streams in which the 

 maximum summer temperature was often as high as 85° F. During the 

 protracted drought many streams almost ceased flowing and most of 

 them were deserted by fishes of all kinds. The most successful attempts 

 to acclimatize the species have been in the Cannon River, where it has 



