CO 



O 



X 



X 



I- 



CL 

 LU 

 Q 



-40 



100 500 



l.n.l.nil 1 I I I 



-50 



80 • ' ' 80- 



January - March April -June July- September October December 



Figure 6. — Availability of chubs (primarily Leucichthys hoyi) to bottom trawls in southern Lake Michigan by depth and 

 3-month periods. The illustration figures represent catch rates of chubs at 5-fathom intervals. 



April through June.- - During most of this 

 period very few chubs were taken in less than 

 20 fathoms; however, toward the end of the 

 period some bloaters moved into shallower 

 water and could be taken at that depth or 

 shallower. The heaviest concentrations were 

 generally in 30 to 45 fathoms. In 50 fathoms 

 and deeper, chub catches dropped off sharply; 

 below 70 fathoms, few chubs were taken. 



July through September.-- In summer, clubs 

 were taken at all depths from 5 to 80 fathoms. 

 At nearly all stations visited during this period, 

 chub concentrations could be found at two 

 distinct depths. Usually one group was con- 

 centrated somewhere between 15 and 25 fa- 

 thoms and a second group somewhere between 

 3 5 and 45 fathoms. 



A comparison of chub catch rates to bottom 

 temperature was made during cruise 19. Al- 

 though some chubs were taken where water 

 temperatures were 39° and 63° F., most were 

 found between 41° and 59° F. Jobes (1949) 

 found the extremes of water temperature to 

 be 34.7° to 52.5° F., and the greater abundance 

 of chubs were in water between 38.8° and 

 44.6°F. 



October through December.-- At this time 

 few bloaters were found inless than 20 fathoms 

 and the largest catches were n-iade between 

 30 and 40 fathoms. Catch rates tapered off 

 beyond 40 fathoms. 



During this study, chubs were taken from 5 

 fathoms (the shallowest depth fished) to 80 

 fathoms. The only drag that was made deeper 



15 



