|Invasions of harp seals Phoca groenlandica Erxleben to coastal waters of Norway in 1995: ecological and demographic implications|
Nilssen, K.J.; Haug, T.; Øritsland, T.; Lindblom, L.; Kjellqwist, S.A. (1998). Invasions of harp seals Phoca groenlandica Erxleben to coastal waters of Norway in 1995: ecological and demographic implications. Sarsia 83: 337-345
In: Sarsia. University of Bergen. Universitetsforlaget: Bergen. ISSN 0036-4827, more
|Authors|| || Top |
- Nilssen, K.J.
- Haug, T.
- Øritsland, T.
- Lindblom, L.
- Kjellqwist, S.A.
Since 1978, and in particular in 1986-1988, large numbers of harp seals Phoca groenlandica Erxleben have invaded coastal waters of North Norway during winter and spring. After 1988 the harp seal invasions have been restricted to the northeasternmost 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. Diet composition, age structure and body condition parameters were examined on seals taken incidentally in Norwegian gill net fisheries during winter and spring in 1995. In early winter immature animals were taken, while mature females dominated in the spring. Analyses of stomach contents suggested that the diet mainly contained fish, in particular saithe Pollachius virens (L.), haddock Melanogrammus aeglefinus (L.) and cod Gadus morhua (L.). 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 southeastern 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 tagged harp seals showed that some of the invading immature seals in the winter of 1995 belonged to the Barents Sea stock. Comparisons of age compositions of the Barents Sea harp seals based on material collected during Norwegian commercial sealing in the East Ice moulting lairs in the period 1978- 1993 with samples from 1995 could suggest a low recruitment to this stock of the 1993 and in particular the 1994 year classes.