WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



359 



of two distinct concentration zones for both legal and undersized fish and in showing a 

 somewhat shallower habitat for the whitefish. The inshore concentrations, in both of 

 which the numbers of fish per lift exceeded those of the offshore concentrations, were 10 

 feet shallower than the maxima for the corresponding size groups in Lake Huron. 

 Consequently, the most suitable limit for the depth of water in which impounding nets 

 should be operated in Lake Michigan is 70 feet, 10 feet shallower than in Lake Huron. 



BATHYMETRIC DISTRIBUTION OF OTHER SPECIES 



Other species were much less numerous in the catches of pound nets and deep trap 

 nets than were whitefish. The data on the bathymetric distribution of these "miscel- 

 laneous" species, therefore, will not be given in the same detail as those on the distribu- 

 tion of whitefish. 



LAKE TEODT 



Nearly all of the lake trout (Cristivomer namaycush) were of legal size (minimum 

 legal weight, IV2 pounds). As undersized lake trout were so few and because there 

 was no evidence of important differences in the vertical distribution of legal and under- 

 sized fish, tables 30, 31, and 32 have been prepared from the records of all trout taken, 

 regardless of size. 



Lake Huron. — In the Alpena-Ossineke area (table 30) lake trout were numerous 

 in May (31.0 to 39.8 fish per lift) at depths greater than 100 feet, but only one trout 

 was taken in the lift from 81-90 feet. In June lake trout were fairly numerous in the 

 shallower water (41-70 feet) while the average catch per lift declined (in comparison 

 with the averages for May) in depths greater than 100 feet. The records for four lifts 

 from depths between 40 and 71 feet in July and August suggest that most lake trout 

 had abandoned the shallower water in these two months. Possibly this offshore move- 

 ment accounts for the increase over the catch for the month of June in the average 

 number of trout per lift from 81-120 feet. The average lifts in August were consistently 

 below those of July from depths of 71-120 feet, and the September catches were smaller 

 than those of August from the 101-120 foot interval. These decreases possibly may 

 represent a movement of the lake trout to depths greater than those in which deep 

 trap nets were operated. 



Table 30. — Number of lake trout per lift of pound nets and deep trap nets in the Alpena- 

 Ossineke area, 1931-1932 



[Number of lifts in parentheses] 



The seasons' averages indicate an irregular trend toward an increase in the abun- 

 dance of lake trout with increase in the depth of the water. The decline in numbers in 

 depths of 101-110 feet may be real since similar decreases occurred in the catch for July 



