New Method of Quantifying Scale Shape and an Application to Stock Identification in Walleye (Stizostedion vitreum vitreum)

Abstract

The planar shape of fish scales may be quantified by a method of unrolling the digitized scale outlines and describing the resultant series by Fourier series. Each scale shape is defined by a vector of harmonic amplitude coefficients and phase angles. Each harmonic in the vector generates a shape component which can be reconstructed graphically. The contribution of each harmonic to the goodness-of-fit between the model shape and the observed scale shape is known. The method was successfully applied to discriminate stock samples of 5-yr-old male walleye (Stizostedion vitreum vitreum) from two locations in eastern Lake Erie.