Yellow perch, Perc4 flavescens (Mitchill), were sampled by bottom trawling and gillnetting in Indiana waters of Lake Michigan near Michigan City, Indiana during the months of June, July and August, 1988.Length-frequency analysis of trawl-caught fish revealed that fish older than age 1 were represented by a single large aggregate in monthly length frequency distributions. Opercular ages were validated by establishing that opercular bone annulus formation occurred from late spring to early summer and was completed by late July.Percent agreement of age determinations by age class between the methods ranged from 0X to 100X for males and OZ to 89X for 'Females for combined months. There was a tendency for percent agreement to decrease with increasing age in both males and females. The majority of the age discrepancies were a difference of plus or minus one year for both males and females.The body-scale length relationship was determined to be linear with data points close to the regression line for both sexes by month and for months combined. Coefficients of determination values ranged from 0.92 to 0.96 for male body-scale length regression by month with a value of 0.93 for months combined . Coefficients of determination values for females ranged from 0.92 to 0.94 by month with a value of 0.93 for months combined. Combining all data for months and sexes yielded a coefficient of determination value of 0.93 for body-scale length regression.The a-values determined for the body-scale length relationship were variable from June through August for both sexes. Male avalues ranged from 30.58 to * 44.15 monthly with a months combined value of 37.63. Female a-values ranged from 25.55 to 43.30 monthly with a combined months value of 34.83. Combining all data for months and sexes yielded an a-value of 35.78.The body-opercular length relationship was determined to be linear with data points close to the regression line. Coefficients of determination values for males ranged from 0.94 to 0.98 by month with a value of 0.96 for months combined. Coefficients of determination for females ranged from 0.97 to 0.98 by month with a value of 0.97 for months combined. The combined data for sexes and months resulted in a coefficient of determination value of 0.97.The a-values determined for the body-opercular length relationship demonstrated variability from month to month. Male a-values ranged from 9.19 to 14.47 monthly with a combined months value of 11.69. Female a-values ranged from 8.83 to 12.26 monthly with a combined value of 11.57. Combining the data for months and sexes yielded an a-value of 11.59.Growth determinations based on scale and opercular data for all aged fish demonstrated a high degree of agreement between the methods for both sexes and all age classes. No significant differences were found between 95X confidence intervals for mean length at formation of last annulus for any age class. The largest observed difference in length at formation of last annulus was 23 mm in the age 3+ females in June. Growth determined from opercular bones was found to be slightly greater than growth determined from scales in both sexes. Females grew faster than males after age 2 based both on scale and on opercular data. Monthly length increment determined from scale and opercular data was determined to be small or non-existent after age 2 for both sexes.Growth determined from scales and opercular bones for only those fish with agreed age between the methods demonstrated a high degree of agreement between methods by month for both sexes. No significant differences were found between 95X confidence intervals of mean length at last annulus in any age class. Data for months combined and sexes separate revealed that growth determinations were virtually identical between the methods. Females were shown to grow faster than males after age 2 for both methods. Monthly length increment was again found to be small or non-existent after age 2.Based on these results, it is concluded that the opercular bone method is an acceptable procedure for assessing age and growth of the yellow perch in Indiana waters of Lake Michigan. Since false annuli were more readily recognized in the opercular bone than in the scales and, since there was the decreasing agreement between the methods with increasing age of fish it is concluded the opercular method is probably a more accurate method for age and growth analysis in the yellow perch from Indiana waters of Lake Michigan. / Department of Biology