The Rate of Growth and Sex Ratio for Seven Michigan Fishes

The average size for the various age groups is presented for seven Michigan fishes: the bluegill (Lepomis m. macrochirus), yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), rock bass (Ambloplites r. rupestris), largemouth black bass (Micropterus salmoides), smallmouth black bass (Micropterus d. dolomieu), and the black crappie (Pomoxis nigro-maculatus). Ages were determined for 25,723 specimens. Only two species showed consistent sex differences in growth rate. The female yellow perch grew more rapidly than did the males, and the male rock bass were consistently larger than the females of corresponding age. Sex ratio for each of the species also is presented. The percentage of males varied from 39 percent in the yellow perch to 52 percent for the pumpkinseed and black crappie. Weights for each of the age-groups were calculated from the length-weight equations.