Allozyme variation was studied on samples of blue mussels from three locati
ons in and around Bergen. After initial studies trying a variety of buffers
and electrophoretic conditions, the enzymes PGM and PGI were chosen for me
asuring intra- and interpopulation variation. Samples were collected from t
hree localities within a maximum distance of about 40 km. High interpopulat
ion variation was observed for distribution of PGM and PGI genotypes and th
eir controlling alleles. It is assumed that selection has differentiated th
e population at the PGM and PGI loci. There is a significant deviation from
the Hardy-Weinberg: equilibrium of the PGM* alleles, which may be explaine
d by selection.