Recent age compositions and aberrant migration patterns of the Barents Sea stock of harp seals Phoca groenlandica

Abstract

Since 1978, and in particular in 1986-1988, large numbers of harp seals Phoca groenlandica have invaded coastal waters of North Norway during winter and spring. After 1988 the harp seal invasions have been restricted to the northeastemmost parts of the coast of Norway. In 1995, however, a significant increase occurred in both the magnitude and the spatial extent of the harp seal invasions. Sampling of stomach contents, teeth for age determinations and body condition parameters were carried out on seals taken as by-catches in Norwegian gillnet fisheries during winter and spring in 1995. In early winter the seal herds comprised immature animals (mainly from the 1994 year class), while mature females dominated in the spring. Analyses of stomach contents suggested that the diet mainly contained fish, in particular saithe Pollachius virens, haddock Melanogrammus aeglefinus and cod Gadus morhua. Body condition parameters revealed that the one year old seals taken in February 1995 were in significantly poorer condition than harp seals of the same age taken in the southeastem Barents Sea in February 1993. Also the mature females taken in April 1995 had significantly lower condition compared to adult females collected in April 1992. Recaptures of 39 immature harp seals tagged in the White Sea (mainly in 1994) suggest that the invading young harp seals in the winter of 1995 belonged to the Barents Sea stock. Age compositions of the Barents Sea harp seals based on material collected during Norwegian commercial sealing in the East Ice moulting lairs in 1995 suggest a low recruitment to this stock of the 1993 and in particular the 1994 year classes.