Harbour seals are distributed along the entire Norwegian coast, with highest densities in Sør-Trøndelag and Nordland. They occur in groups of 10–20 animals to some hundred seals. Pups are born in late June, and they start to swim from day one. Harbour seals are stationary and are managed within counties in Norway. Taggings (traditional flipper tags and satellite tags) have shown distribution areas of 70–80 km, which suggests local populations in Norwegian waters. Preliminary genetic results confirm that there are several local populations. A genetic sampling project has been started to explore the harbour seal population structure in Norwegian waters.
Both grey and harbour seals are exploited in a quota hunt. Management is based on nationwide countings of populations every five years.
Approximately 6700 harbour seals were recorded during moult in 2003–2006, indicating an annual population decline of about 1.5% from the previous count of 7500 animals in 1996–1999. Due to this decline and high hunting pressure, the harbour seal was listed as vulnerable on the 2006 Norwegian Red list. Vulnerable is a category that indicates that there is a 10% probability that the species will disappear from the Norwegian areas within a hundred years if current exploitation levels persist. In addition to harbour seals along the Norway mainland coast, the world's northernmost population of harbour seals is found on Prins Karls Forland in Svalbard. This isolated population is protected, and estimated to be in excess of 1000 individuals.
Harbour seals spend most time on land during moult, therefore population counts are carried out during this period. Counting is done using aerial photography and visual counts on all known localities. Monitoring is carried out during the day and at low tide, preferably under good weather conditions since most seals are hauling out then. Based on correction factors for seals in the water, obtained from Swedish and Norwegian studies, the total population of harbour seals in Norway was estimated at approximately 10 000 individuals, based on the 7500 observed animals in 1999. New nationwide counts of harbour seals have started up, and a new total estimate is expected to be ready in 2013.