^Q U. S. BUREAU OF FISHERIES 



AGE AND GROWTH STUDIES 



Lake Erie sheepshead. — An investigation of the Lake Erie slieeps- 

 liead (ApJodinotus grutniien.s) by Dr. Van Oosten included data on 

 growth rate, growth compensation, the age and year-class composi- 

 tion of the stock, the relationship of total and standard length, the 

 length- weiglit relationship, and the coefficient of condition. Although 

 one fish in its thirteenth year and another in at least its seventeenth 

 year (this latter fish was 27.2 inches long) were found, the bulk of 

 the collection was made up of young fish. The dominant age-group 

 -vvas the I-group (1926 year-class) with an average length of 8.6 

 inches. 



Other facts brouglit out Avere : growth compensation occurs in the 

 sheepshead; the ratio, standard length in total length, decreases with 

 growth; the coefficient of condition increases with age but is not 

 correlated with growth rate. 



LaJi^e Erie yellow perch. — The investigation of the life history of 

 the yellow perch {Perca -flaveHeenf<) of Lake Erie, suspended in 1935, 

 was resumed in August 1937, upon the return of Frank W. Jobes to 

 the Great Lakes staff. The preparation of a manuscript dealing with 

 the age and growth of the yellow perch in Lake Erie is now under 

 way. The comparison of the growth of the sexes in the yellow perch 

 reveals an unusual situation. In the first year of life the males grow 

 more rapidly than the females, but in all later years the females have 

 the better growth. 



An integral part of the growth study is the examination of the body- 

 scale relationship as determined from measurements of selected or 

 "key" scales. From the ])reliminary tabulation of the material it 

 appears doubtful whether any simple mathematical formula can be 

 employed in the calculation of the growth of the Lake Erie yellow 

 perch. The use of a purely empirical curve of the body-scale rela- 

 tionship may prove necessary. 



The coefficient of condition was found to vary according to locality 

 and season. Sex differences occur only in the spawning season at 

 which time the females luive distinctly the higher coefficient. The 

 study of season variation revealed that condition is best during the 

 summer. 



Lake Erie ichifefish. — After a lapse of several years the study of the 

 Lake Erie whitefish {Coregonus clupeafomiis) has been resumed. All 

 scales have now been read, and measured, and the individual growth 

 Mstories calculated. Data relative to the various phases of the life 

 history of the Lake Erie whitefish have been compiled in tabular form 

 preparatory to writing a report on this subject. 



FOOD or LAKE MICHIGAN LAKE TROUT AND LAWYERS 



A report on the quantitative and qualitative analysis of the contents 

 of 4,979 lake trout {Cristivoiner namaycusK) stomachs and of 1,528 

 lawyer {Lota 7)iaculosa) stomachs was completed by Drs. Van Ooosten 

 and H. J. Deason. The food of the trout consisted of 98 percent by 

 volume of fish of which Cottidae and Coregonidae were the principal 

 constituents. Cottidae were dominant in southern Lake Michigan 

 (72 percent by volume), Coregonidae in northern Lake Michigan (51 

 percent), but the lake shiner {Notropis atherinoides) was most im- 



