ALLOMETRY AND ANALYSIS OF MORPHOMETRIC VARIATION IN THE BLUEGILL, LEPOMIS-MACROCHIRUS

The use of multivariate descriptions in studies of morphometric variation is increasing. This paper uses three different methods to describe the morphology of bluegill of a common random genetic background reared from larvae in four experimental ponds, the fish of each pond differing in average growth rate. The methods are similar in detecting differences in overall growth between males and females, but differ in their description of size-adjusted body plan. Analysis of centroid and truss lengths indicates that males possess stouter caudal peduncles; analysis of polar coordinates indicates that males have more "upright" heads. All methods show that males have longer pectoral and pelvic fins and that their fins are located more anteriorly. These analyses suggest that the way researchers adjust for allometric growth and size differences has consequences for the visualization of shape differences. As such, it may be necessary to use several methods of morphometric analysis in fishes, especially when exploring for axes that may be correlated with ecological functions.