46 



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■ ■-. -,K V 



Figure 12. — Typical raceway construction for spawning chubs. 



A. Diagrammatic view of 

 stream bed and shelters. 



B. Cross section of spawn- 

 ing area. 



Michigan Conservation Department 



netting over the stream bed for control of predatory 

 birds. 



The main channel (6 feet wide, 1 foot deep, and 

 300 feet long) was dug within the basin of a 1. 8-acre 

 pond. Starting at the inlet,' following along the base 

 of one of the dikes, the excavation gradually descended 

 (8 inches fall per 100 lineal feet) into the basin of 

 the pond. The materials removed from this ditch were 

 placed on both sides of the channel, forming 1. 5- foot 

 banks. At intervals of 25 feet along the course, 

 rectangular pits (2 feet deep, 3 feet wide, and 8 feet 

 long) were prepared. These pools, hereafter to be 

 referred to as refuge zones, crossed the stream bed 

 and extended into one of the banks for a distance of 

 about 4 feet (upper drawing, fig. 12). That portion 

 extending into the bank was curbed to prevent filling 

 by erosion. At this point of construction the entire 

 stream, including those portions of the refuge zones 

 lying within the channel and both banks, was surfaced 

 with a 6-inch layer of washed gravel (1/4- and 3/4-inch 



