PROGRESS IN BIOLOGICAL INQUIRIES, 1922. 5 



during the remaining years of life. The pilot grows more slowly 

 than the whitefish and herring during the first three years and ap- 

 IDroaches the rate of growth of the whitefish in the fourth and fifth 

 years and that of the herring in the sixth and seventh years of life. 

 The blackfin appears to grow more slowly than any of the above three 

 species during the first six years of life. The 5 and 6 year blackfins, 

 for example, average the same in length as the 4 and 5 year herrings ; 

 the 6-year blackfins average the same as the 4-year pilots, while the 

 7-year blackfin is no larger than the 3-year whitefish. After the 

 sixth year the blackfins increase their rate of growth. 



Concerning the growth of the very young specimens nothing is 

 known from actual measurement, as these specimens are up to the 

 present time unobtainable. The youngest specimens in the collec- 

 tion are 2-year herring and whitefish, 3-year pilots, and 5-year 

 blackfins. 



The maximum sizes are more or less completely represented in the 

 collection, so that the maximum ages can be determined. It was 

 found that the "herring" (of the four species considered) possessed 

 the shortest life span and the whitefish the longest. The maximum 

 ages were as f ollow^s : " Herring," 8 years ; pilots, 13 years ; blackfins, 

 13 years; and whitefish, 17 years. 



Both mature and immature specimens are represented. The age at 

 sexual maturity for some of the species seems to vary with locality. 

 Thus the whitefish from Kagawong and Mindemoya may mature at 

 the age of 4 years and those from Bay City, East Taw^as, Cheboygan, 

 and Gore Bay at 5 years, but those from Alpena and Killarney do 

 not appear to mature before the sixth year. Likewise the age at 

 sexual maturity of the pilots seems to vary with the locality. At 

 Kagawong this species may mature at 4 years, but those from ports 

 on Lake Huron do not seem to mature before the fifth year. The 

 blackfins mature in their seventh year, irrespective of the port from 

 which they are taken. The herring matures in the third year. Per- 

 haps the pilots and whitefishes of this water are composed of different 

 races. 



In order to determine the average length of life of all the valuable 

 coregonine species of the Great Lakes, as well as to secure more 

 reliable data on other questions of interest concerning these fish, it is 

 desirable that larger and more representative collections be made 

 and studied. 



FISHES OF CHESAPEAKE BAY. 



The extensive study of the fishes of the Chesapeake Bay, begun 

 just before the close of the fiscal year 1921, was continued through- 

 out the year 1922. The field work was conducted by W. C. Schroeder, 

 utilizing the fisheries steamer Fish Hawk^ and the materials were 

 studied by Samuel F. Hildebrand and W. C. Schroeder, scientific as- 

 sistants, with cooperation from Prof. Edwin Linton, temporary in- 

 vestigator, in the analysis of the food of fishes. In the field work it 

 is endeavored to collect not only representatives of all fishes found 

 in the bay, so far as practicable, but to obtain fishes of all sizes and 

 at all seasons in order to gain information upon rate of growth, 

 spawning seasons and locations, maximum sizes obtained, and other 

 questions of importance. Large numbers of stomachs of fish are pre- 



