STUDIES ON THE STRIPED BASS Of THE ATLANTIC COAST 31 



lateral fields at the focus. (See fig. 15.) Scales from striped bass that were beyond 

 their fifth year were not used, since the annuli were often indistinct and it was there- 

 fore difficult to make precise measurements. Van Oosten (1929), Creaser (1926), 

 and others have pointed out that the validity of the scale method of determining the 

 length of a fish at different years in its life depends on 3 main factors: (1) That the 

 scales remain constant in number and identity throughout the life of the fish; (2) 

 that scale growth is proportional to the growth of the fish; and (3) that the annuli 

 are formed yearly and at the same time of the year. Since it has been proved in 

 many other species that scales do maintain their identity throughout the life of the 

 fish, and because there is no evidence to the contrary in the striped bass, it has been 

 assumed that the first requirement holds true. In testing the relation of scale 

 growth to the growth of the fish, the radii of scales from 153 bass of measured length 



40 SO 



FISH IN 



SO 



CMS 



LENGTH 



Fiouee 21.— The relationship of scale growth to body growth in the striped bass (see Table 15 for original data). 



from 10.5 to 67 cm. were plotted against the lengths of the fish. (See fig. 21.) It 

 will be noted that there is a good straight-line relationship, and that therefore the 

 scale growth may be considered proportional to the growth of the fish within the 

 limits studied. There is no proof, however, that scale and body growth are pro- 

 portional in the smaller sizes below 11 cm., or in the extreme larger sizes above 67 

 cm. The formation of annuli has already been discussed, and there can be no doubt 

 that they are formed yearly and at the. same time of year — during the winter. 



Since all the larval stages of development of the striped bass were not available, 

 it was impossible to determine the factor C (that length at which scales first appear 

 on the fish) by careful examination of preserved material. Bass down to 2.0 cm. 

 were collected in the field, and these all showed prominent scales. Individuals up to 

 0.5-0.6 cm. (approximately 8 days after fertilization of the eggs and 6 days after 

 hatching) were preserved from the hatchery at Eden ton, N. C, and these did not show 

 any signs of scale formation. It was therefore necessary to estimate at what length 

 scales first appear on striped bass between 0.6 and 2.0 cm. by other means. The 

 material that forms the basis of figure 21 was used for this purpose. A regression 

 equation expressing the body-scale growth relationship of the striped bass was 



277589 — 41—3 



