388 



BULLETIN OF THE BUKEAU OF FISHERIES 



from the other localities considered are no greater than these differences between the 

 3-year fish taken at Gravelly Point on different dates. 



No striking differences exist in the computed growth rates and lengths of the 

 4-year fish of the four localities under consideration; but the 5-year herring from 

 Gravelly Point seemed to have had a faster rate of growth than those from the three 

 other localities, while the 6-year fish from Gravelly Point appeared to have grown 

 less rapidly than those from Tobico. The differences are not consistent. 



The data of Tables 53 and 54 show that the Tobico, Nayanquing, and Au Gres 

 herring undoubtedly belong to the same general population. The data of the Grav- 

 elly Point herring are not conclusive but they suggest that in all probability the 

 Gravelly Point fish are not different from those taken farther south in the bay. On 

 the basis of growth rate we apparently can not separate the herring population of 

 Saginaw Bay into distinct races. 



VARIATIONS IN RATES OF GROWTH OF HERRING FROM DIFFERENT LOCALITIES IN 



LAKE HURON 



The discussion so far has involved only the herring taken in Saginaw Bay, the 

 principal herring grounds of Lake Huron; but it is of extreme interest and of economic 

 importance to compare the Saginaw Bay herring with those of other locahties, espe- 

 cially as regards their rate of growth, for a difference in rate of growth of herring in 

 different localities might afford evidence of local races. The only material at pres- 

 ent available for this comparative study is that collected by Doctor Koelz in 1917 

 and 1919 and by me at Oscoda, Mich., in 1922. This material does not include, for 

 the present study, an adequate number of individuals for all the localities at which 

 collections were made. (See Table 1.) 



Table 55. — Range in length, modal length, average length of sample, percentage of abundance of each 

 age group, percentage of males and females in each age group, and percentage of immature and mature 

 fish in each age group for herring taken November 1, 1922, at Bay City, and November 2, 1922, at 

 Oscoda, Mich} 



' The number of specimens employed is shown in parentheses. 



