Harbour seal (Phoca vitulina) diet in Vesteralen, north Norway

Results from analyses of stomach contents and faeces collected from harbour seats (Phoca vitulina) in Vesteralen, north Norway, in 1990-1995 revealed a diet comprised mainly of saithe (Pollachius virens). Little variation occurred in the diet throughout the year, probably due to a large and stable abundance of saithe in the area. Other prey items that seemed to be important were herring (Clupea harengus), cod (Gadus morhua), sandeel (Ammodytes sp.) and various flatfishes. The harbour seals seemed to prefer small fish, and older seals appeared to have a more varied diet than the younger animals. In a captive study, the recovery of otoliths was only 14.8% when harbour seals were fed whole fish. Recovery rates varied between species: 4.6, 47.7 and 46.6% of herring, haddock (Melanogrammus aeglefinus) and cod, respectively. The results from the captive study were used to illustrate potential biases in observed diets based on faeces.