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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



intervals, and the corresponding average total 

 lengths in inches, together with the average scale 

 measurement (at magnification X 40.7), and the 

 body-scale (L/Sc) ratios of each length and age 

 group. The L/Sc ratios of the age groups are 

 the averages for data collected both at the end 

 of the growing season and at various times 

 throughout the summer (see p. 211). The data 

 were originally grouped in 5-mm. length intervals, 

 but careful examination revealed that condensa- 

 tion to 10-mm. intervals was justifiable. The 

 average L/Sc ratios of the age groups indicate that 

 the relative size of the scale increased during the 

 first 3 years of life and then decreased slightly 

 during the fourth. However, a comparison of 

 the L/Sc ratios of fish in the same length interval 

 but of different ages revealed that there was no 

 consistent change in the relative size of scale with 

 age. Consequently, the differences between the 

 relative sizes of scales in the different age groups 

 do not depend directly on age but rather on the 

 length distribution of the age groups. Com- 

 parisons between fish in the same age group but 

 of different average lengths showed that the 

 L/Sc ratios became relatively smaller (relatively 

 larger scales) as the fish length approached 4.3 

 inches (see data for age groups and I) ; remained 

 reasonably constant over the length range of 4.3 

 to 9.2 inches (age groups I, II, and III); and then 

 established another reasonably steady but higher 

 ratio (relatively smaller scales) over the length 

 range of 9.2 to 10.9 inches (age groups II and III). 



-Body length io scale length ratio (L/Sc) of selected scales from western Lake Erie yellow perch by 10-mm. intervals 



(Number of specimens in parentheses) 



Only key (selected) scales were used to determine 

 the relation between size of scale and size of fish. 

 The scale on the left side of the fish in the third row 

 below the lateral fine and directly beneath the 

 sixth spine of the dorsal fin was designated the key 

 scale. The position of the key scale approximated 

 the center of the area from which the unselected 

 scales were obtained for age and growth determina- 

 tions. The scale occupying the designated posi- 

 tion on the right side of the specimen was used 

 when the one on the left side was lacldng or was 

 regenerated or malformed. Although the collec- 

 tions for the key-scale study were taken at widely 

 spaced intervals of time (see p. 211), an analysis of 

 the data failed to reveal any large or consistent 

 differences for fish captured in different years or 

 seasons.' There is no evidence of a seasonal lag 

 between the growths of body and scale in the Lake 

 Erie yellow perch. The data also failed to show 

 any consistent differences in the relative sizes of 

 scale correlated with sex or stage of maturity. 

 Therefore, data from all fish have been combined 

 in this study without regard for the time of capture, 

 sex, or stage of maturity. 



Table 3 shows the average standard length of 

 the Lake Erie specimens grouped in 10-millimeter 



' Tlie scales of group (first year of life) yellow perch caught during late 

 October and early November 1928 were found to be consistently somewhat 

 smaller than the scales from fish of the same length and the same year class 

 that were caught during September 1928 and June 1929. This unusual 

 phenomenon cannot be explained satisfactorily at present. However, the 

 differences were so small that the inclusion of fish caught during October and 

 November did not change greatly the grand average ratio of body length to 

 scale length (table 3) . 



Table 3.- 



> First year of life. 



» The age was not determined for 1 specimen in this length interval. 



