MORPHOMETRIC COMPARISONS OF SKULLS OF HARBOR PORPOISES (PHOCOENA-PHOCOENA) FROM THE BALTIC, KATTEGAT, AND SKAGERRAK SEAS

The population structure of harbour porpoises (Phocoena phocoena) in S wedish waters was studied by means of morphometric comparisons of skul ls from 103 specimens, The study was designed to investigate whether h arbour porpoises in the Baltic Sea form a distinct population separate from animals found in the Kattegat and Skagerrak seas. The Kattegat-S kagerrak (K-S) sample was divided into summer and winter samples to ac count for possible migrational movements by Baltic Sea animals between breeding seasons. Both multivariate and univariate statistical analys es showed significant differences between three female samples from th e Baltic Sea and the Kattegat and Skagerrak seas. Pairwise comparisons showed differences between the Baltic sample and the K-S summer sampl e in five characters and between the Baltic sample and K-S winter samp le in one character. No differences were found between the K-S summer and winter samples. The multivariate analysis did not show separation of male specimens and only one character was significantly different i n the univariate analyses. Pairwise comparisons of adjusted means of t his character did not reveal significant differences between the sampl es. The results show that female harbour porpoises in the Baltic Sea a re morphologically distinct from females in the Kattegat and Skagerrak seas and these differences probably would not exist if animals from t he two areas interbreed. Harbour porpoises in the Baltic Sea should th erefore be managed separately and measures should be taken to prevent bycatches of this likely endangered population.