WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



355 



Table 28. — Number of legal and illegal whitefish per lift of pound nets and deep trap nets in northeastern 

 Lake Michigan (ports of Manistique, Epoufette, and Naubinway), 1931-1932 



[Number of lifts in parentheses. Asterisks indicate concentrations] 



deepest water (more than 110 feet). The zones of concentrations of illegal fish (seasons' 

 average) are separated by 30 feet (difference between average depths of the intervals) 

 as compared with 20 feet in the legal fish. This same difference is to be found in the 

 data for the three months — June, July, and August — but is lacking in October (rela- 

 tively incomplete data, however). 



In general, undersized whitefish tended to live in shallower water than did legal-sized 

 individuals. This tendency is apparent not only from the lesser depth of the inshore 

 concentration zone (71-80 feet for illegal fish and 81-90 feet for legal fish) but also 

 from the large numbers of small whitefish per lift in the still shallower interval, 61-70 

 feet. Legal-sized fish were slightly the more numerous, however, at depths shallower 

 than 61 feet. 



.The vertical movements of the whitefish in northeastern Lake Michigan are the 

 reverse of those indicated by the Lake Huron data for the Alpena-Ossineke and Sag- 

 inaw Bay areas (pp. 350 and 3511. In each of these regions of Lake Huron the 

 data indicated an onshore movement of both legal and undersized fish during the sum- 

 mer. Whitefish of both size groups made an offshore movement in northeastern Lake 

 Michigan. 



Possible significance of two concentration zones. — The occurrence of two concen- 

 tration zones of both legal and illegal whitefish in northeastern Lake Michigan 32 raises 

 the interesting question of the possible existence of distinct inshore and offshore popula- 

 tions or races. Certainly, the consistency of the occurrence and the seasonal move- 



32 There was some indication of a similar distribution of whitefish on the Alpena-Ossineke grounds (p. 350). 

 (p. 351) offered only a suggestion of two concentration zones. 



The data for the Saginaw Bay area 



