Evaluation of scale shape for identifying spawning stocks of coastal Atlantic striped bass ( Morone saxatilis)

We review a numerical method of associating fish of unknown stock affiliation with their respective spawning stocks on the basis of differences in quantified scale shape. Magnified images of fish scales are digitized and the shapes of the scales are transformed into a mathematical relationship (Fourier series), from which the original shape can be regenerated with little loss of resolution. A multiple, stepwise discriminant analysis is used to characterize each putative stock within a fishery on the basis of the shape of the scales from fish in the population. Also, classification criteria are developed by which individual fish can be assigned to their respective stocks on the basis of scale shape. The shape of scales of Atlantic striped bass, Morone saxatilis, was characterized to evaluate the use of the method for this fishery. Differences in scale shape between Hudson River and Chesapeake Bay fish were sufficient to allow classification of individuals to their area of origin with 80% accuracy. To demonstrate the use of the procedure, we estimated, from 89 striped bass scales taken in the Rhode Island November 1982 fishery, that 45% were from the Hudson River and 55% from Chesapeake Bay. Similarly, from 100 scales taken from fish in the eastern Long Island April–December 1982 fishery, 53% were of Hudson River origin and 47% were from Chesapeake Bay.