Report of the International Whaling Commission (1980)


Dentinal growth layer groups (GLGs) in teeth were counted for 84 beach-cast specimens of Phocoena phocoena from the northeastern Pacific (mostly California). Measurements of external, cranial, and postcranial traits were found to be related to growth layer groups in most cases. Of the traits related to dentinal layering 70% were found to be sexually different in the slope of the relationship. Growth of the body posterior to the dorsal fin was more rapid and extensive in females as compared to males, especially during and after the attainment of sexual maturity. The growth curves of total length and length of longest rib showed a retardation in growth earlier in males (about three GLGs) than in females (about five GLGs). The total length growth curve for females closely resembled the juvenile growth phase for both sexes of Stenella attenuata.