360 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



and August. The decline in depths greater than 120 feet may be the result of the lack 

 of data for months later than June. 



It should be emphasized that, in contrast to the whitefish data, those presented for 

 the lake trout on the Alpena-Ossineke grounds and in other areas should not be taken 

 as descriptive of the general distribution of trout in Lake Huron and northern Lake 

 Michigan. The chief summer fishery for trout is conducted by gill nets at depths con- 

 siderably greater than those from which the pound nets and deep trap nets were lifted. 

 The data given here describe only the distribution of the presumably sparse inshore 

 population of trout. 



Lake trout were considerably less abundant in the Saginaw Bay area (table 31) 

 than off Alpena and Ossineke. In four of the six months (all but July and September) 

 the largest lifts were made from the deepest water (more than 120 feet). Trout were 

 scarce in shallow water (less than 61 feet) in June and were not taken at all in July 

 and August. The data fail to indicate whether the improved catches beyond 90 feet in 

 July and August were the result of an offshore movement of an inshore group of trout or 

 of an onshore movement of an offshore group. The averages for September and possibly 

 October are suggestive of a migration toward deeper water. 



Table 31. — Number of lake trout per lift of pound nets and deep trap nets in the Saginaw Bay area (ports 

 of Au Sable-Oscoda, East Tawas, and Bay Port), 1931-1982 



[Number of lifts in parentheses] 



The seasons' averages show a general tendency for the number of lake trout per 

 lift to increase with increase in the depth of water. 



Tabular data are not given on the bathymetric distribution of lake trout in northern 

 Lake Huron (Cheboygan and Rogers City area) and on the Harbor Beach grounds. 

 (For the number of lifts at the various depths of water at these localities see tables 

 23 and 26.) The average number of trout per lift in northern Lake Huron varied 

 widely (from 1.5 to 76.5 fish) with the best catch in 81-90 feet in August. Lake trout 

 were fairly scarce on the Harbor Beach grounds. The best catches were: 20.3 fish per lift 

 from 111-120 feet in August; 19.8 fish from depths greater than 120 feet in August; 

 and 15.5 fish from 111-120 feet in September. Catches of lake trout were uniformly 

 small in water shallower than 101 feet. In October only three trout were taken in a 

 total of nine lifts, all from depths greater than 90 feet ; apparently the lake trout had 

 migrated from the Harbor Beach deep-trap-net grounds in that month. 



Lake Michigan. — The rather extensive data from northeastern Lake Michigan 

 (table 32) suggest that in certain months the lake trout as well as the whitefish may 

 occur in two concentration zones. (See p. 353, table 28, and fig. 22.) In June and 



