Age and Growth of Walleyes in Clear Lake, Iowa, 1935–1957

Abstract

Interpretation of walleye (Stizostedion vitreum vitreum) scales by three investigators revealed some differences in detail, but the data derived appeared to be basically reliable. Most fish were collected in experimental gill nets. Lengths at annuli were calculated using straight-line relationship with an intercept of 3.26 inches, total length. Growth rate of a year class, as indicated by mean length at the third annulus, was negatively correlated with abundance of the year class (r = −0.78, 11 d.f.). Walfordˈs growth transformation did not give an entirely satisfactory fit but gave a maximum length of 31.1 inches and a k of 0.836. Variations in these values with different treatment of the data were indicated. Fitting a Walford transformation to increments gave: Lt+1 = 28.8 inches (0.172) + 0.828 Lt. The correlation coefficient, r, between the annual increment indexes and the mean May to September temperatures was 0.565. Adding April and October temperatures lowered the correlation. Instantaneous growth rates, i, decrease rapidly with age and with increased length. Several indexes to growth during calendar years using i values and Parker and Larkinˈs Lz values, were tried, but the Hile increment indexes gave the best correlation with summer temperatures. Growth of female walleyes was faster than that of males.