MARINE MAMMAL SCIENCE, 12(4):516-527 (October 1996) 0 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1996 by the Society for Marine Mammalogy zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR GEOGRAPHICAL VARIATION IN METRIC SKULL CHARACTERS AMONG PROPOSED SUBPOPULATIONS AND STOCKS OF HARBOR PORPOISE, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA PHOCOEnA PHOCOENA, INTHE WESTERN NORTH ATLANTIC ANLI GAO D. E. GASKIN Department of Zoology, University of Guelph, Guelph, Ontario, Canada NlG 2Wl ABSTRACT A total of 433 skulls of harbor porpoises, Phocoena phocoena, were examined to evaluate geographical variation within the western North Atlantic, using analysis of covariance and discriminant analysis based on 45 measurements of skull components. The relationship between condylobasal length and body length was sigmoid in both sexes. Condylobasal length is generally less in adult males than in adult females. Despite some overlap, morphological differences between different regions and even adjacent local stocks could be recognized by ANCOVA and discrim- inant analysis. The percentage of correct classification by discriminant func- tions was 65.2% for the four regional samples: (1) North Canadian Atlantic (which includes Gulf of St. Lawrence and Newfoundland), (2) Bay of Fundy, (3) Gulf of Maine-New York, and (4) Maryland-South Carolina. It was 65.9% for the four local geographical areas (10s of km) within the Bay of Fundy; Quoddy-region porpoises revealed a closer relationship with the south- western Nova Scotia population than with other adjacent stocks. The results at this level imply that gene flow is restricted to some degree even among closely adjacent geographical units. Management of this species should aim, therefore, for conservation of a variety of local stocks. Key words: harbor porpoise, Phocoena phocoena, skull morphometry, sexual dimorphism, geographical variation, multivariate analysis, subpopulation, stock, North Atlantic. The harbor porpoise, Phocoena phocoena, is distributed widely in temperate and subarctic coastal waters in the northern hemisphere. The existence of three different continental populations in the North Pacific, western North Atlantic, and eastern North Atlantic was proposed by Yurick (1977) and Yurick and Gaskin (1987). Amano and Miyazaki (1992) postulated a distinct western 516