Size and Age of Freshwater Fishes 



507 



THE RELATION OF SIZE TO AGE IN SOME COMMON 

 FRESHWATER FISHES. 



Homer R. Bolen, Indiana University. 



On the scales of most of our common fishes are a series of con- 

 centric rings. They may be readily seen under a low power microscope. 

 These rings form alternate dark and light bands due to being closer 

 together in some regions than in others. The dark bands represent peri- 

 ods of slow growth and the light bands periods of rapid growth. Since 

 growth is dependent upon food, the dark bands are undoubtedly formed 

 during winter when feeding is partially suspended. Thus by counting 

 the "winter check" bands we can determine the age of the fish. 



Figs. 1-4. Graphs showing rate of growth. The abscissa is the age in years, the 

 ordinate the average length in centimeters. 1, Lcpmnis pallidus (Mitch.), Winona Lake; 

 2, L. 'pallidus. Shoe Lake; 3, Perca flavcsccns (Mitch.), Winona Lal\e ; 4, Microptci~us 

 sabnoides (Lacepede). 



During the summer of 1923, at the Indiana University Biological 

 Station, Winona Lake, Indiana, an attempt was made to determine the 

 relation existing between age and size of some of the common fishes.^ 

 Data were collected on three species: bluegill, Lepomis pallidus (Mitch- 

 ill) ; yellow perch, Perca flavescens (Mitchill) ; and large-mouthed black 

 bass, Micropterns sabnoides (Lacepede). 



All the specimens were secured from Eagle (Winona) Lake with 

 the exception of one lot of bluegills from Shoe Lake and a few black 

 bass from other lakes. All of these lakes are located in Kosciusko 

 County, Indiana. Scales were secured from different parts of the body 

 and placed in paper envelopes on which were written all the data se- 

 cured on each individual, viz., date, species, weight, and length to base 

 of caudal fin. Subsequently the scales were examined under a low power 

 microscope and the age of the fish determined; after which the follow- 

 ing tables (Tables I to IV) were compiled and graphs (figs. 1 to 4) 

 constructed. 



^ This work was taken up at the suggestion of Dr. Will Scott to whom I am in- 

 debted for advice and direction. 



"Proc. Ind. Acad. Sci., vol. 33, 1923 (1924)." 



