WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



361 



July inshore concentrations occurred at 61-70 feet and offshore peaks at more than 110 

 feet. The offshore concentration in August was still in deep water but the inshore 

 maximum was at 81-90 feet or 20 feet deeper than in June and July. (The August 

 data were inadequate, however, for depths of less than 71 feet.) The data for Sep- 

 tember and October yield no evidence of two concentration zones of lake trout in 

 these two months. Data were lacking, however, for depths beyond 110 feet. 



Table 32. — Number of lake trout per lift of pound nets and deep trap nets in northeastern Lake Michigan 



(ports of Manistique, Epoufette, and Navhinway), 1931-1932 



[Number of lifts in parentheses. Asterisks indicate concentrations] 



There was no general agreement as to the actual location of the concentration 

 zones of lake trout and whitefish. It is true that lake trout, large (legal) whitefish, 

 and small (illegal) whitefish (table 28) were all concentrated at 61-70 feet in June 

 and that both trout and legal whitefish exhibited peaks at 81-90 feet in August. On 

 the other hand, the inshore concentration of lake trout was shallower in July than 

 the concentration of either the legal or illegal whitefish. and the offshore concentra- 

 tions of lake trout in June, July, and August were without exception deeper than the 

 concentrations of whitefish. In October, however, a peak was evident at 101-110 feet 

 in both lake trout and the whitefish (large and small). 



Possibly it is not strictly proper to term as "concentrations" the increased abun- 

 dance of lake trout at depths in excess of 110 feet, for these increases in the number 

 per lift may be merely part of a general trend for trout to become more plentiful with 

 increase in depth of water and not, as the term concentration implies, be indicative of 

 a peak abundance bordered on either side by a lesser abundance. 



The data of table 32 as a whole point toward an offshore movement of lake trout 

 in northeastern Lake Michigan from June to October. (A few trout appear, how- 

 ever, to have returned to shallow water in October.) The seasons' averages show an 

 increase in the catch per lift from shallow water (less than 41 feet) to a peak at 

 61-70 feet, followed in turn by a decline through the depth interval, 71-100 feet, and 

 a secondary rise beyond 100 feet. 



In the Green Bay region of Lake Michigan the best catches of lake trout were 

 made in 41-60 feet in May (19.8 fish per lift). The September catches varied but lit- 

 tle with depth of water, averaging 6.8 fish for 13 lifts in 41-80 feet and 5.0 for 4 lifts 

 in 91-110 feet. 



YELLOW PIKE 



Yellow pike (Stizostedion vitreum) occurred in large numbers in the lifts of pound 

 nets and deep trap nets only in the Saginaw Bay region (table 33). Because of the 

 concentration of yellow pike in the shallower water of the area it was considered desir- 



