|dc.contributor.author||Kjellqwist, Sten Anders||
|dc.identifier.citation||This report is not to be cited without prior reference to the authors||no_NO
|dc.description.abstract||Data 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 area||no_NO
|dc.title||Trends in growth and reproductive parameters of Barents Sea harp seals||no_NO
|dc.subject.nsi||VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Resource biology: 921||no_NO