Show simple item record

dc.contributor.authorKjellqwist, Sten Anders
dc.contributor.authorHaug, Tore
dc.contributor.authorØritsland, Torger
dc.date.accessioned2012-08-13T12:12:58Z
dc.date.available2012-08-13T12:12:58Z
dc.date.issued1993
dc.identifier.citationThis report is not to be cited without prior reference to the authorsno_NO
dc.identifier.urihttp://hdl.handle.net/11250/104541
dc.description.abstractData from reproductive organs of Barents Sea harp seals Phoca groenlandica with corresponding age determinations have been analysed in combined samples collected during three periods: 1963-1972, 1976-1985 and 1990-1993. A Gompertz growth model, fitted to the age and standard length (available only from the first and last sampling periods} data, suggest a trend of decreasing growth rates and reduced maximum lengths for both sexes in the most recent period. Testes weights indicate that males attained sexual maturity in age groups 6-9 years during 1990-1993 . This is confirmed by testes volumes which also suggest an apparent increase in age at sexual maturity for males from age groups 4-7 years in the combined 1963-1972 sample. Cumulative maturity frequencies, based on ages at first ovulations as indicated by corpora lutea and albicantia formed within the last two years prior to the year of capture, show that the apparent mean age of maturity for females increased significantly from 5.5 years in the 1963-1972 sample to 6.7 years in 1976-1985 and 8.1 years in 1990-1993. A limited number of mature females sampled after implantation in September-October 1990-1993 indicate a rate of early pregnancies of about 0.84. Temporal changes in fertility may be revealed by future analyses of data from ovaries in the samples. The changes demonstrated in growth and reproductive parameters may presumably be explained as density-dependent responses to population growth in relation to a decreaseing availability of staple food in the Barents Sea areano_NO
dc.language.isoengno_NO
dc.publisherICESno_NO
dc.subjectharp sealno_NO
dc.subjectgrønlandsselno_NO
dc.titleTrends in growth and reproductive parameters of Barents Sea harp sealsno_NO
dc.typeWorking paperno_NO
dc.subject.nsiVDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921no_NO
dc.source.pagenumber24 s.no_NO


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record