A paper published by ICES shows that the harp seal invasions along the Norwegian coast in 1987 and 1988 consumed 215.000 tonnes of fish. The estimated number of individual fish consumed during these two extreme invasion years seems enormous - approximately 110 000 000 000 000 individual cod and saithe of the 1985 and 1986 classes became seal food. The seals’ diet consisted mainly of saithe (33%), cod (19%) and herring (10%). “This order of predation agrees well with the observed sudden decline of these year classes,” the report concludes. Saithe and cod occured at unusually high frequencies since the animals were feeding in coastal waters. The seals stayed along the coast for only 3-4 months in both 1987 and 1988.

The primary author of the ICES paper of March 1993, was K. I. Ugland from the University of Oslo. Ugland took samples from the stomachs of 275 seals in three different areas. The various species of fish in the seals’ stomachs were identified by otoliths and other hard remains. The seals had been entangled in gill nets.