Ea. Petrov et al., AGE-SEX STRUCTURE AND POTENTIAL FOR REPRO DUCTION OF PUSA-SIBIRICA (PINNIPEDIA, PHOCIDAE), Zoologiceskij zurnal, 76(6), 1997, pp. 743-749
Dynamics of sex-age pattern and reproductive potential of the Baikal s
eal population (Pusa sibirica Gm.) based on the data obtained in sprin
g and autumn expeditions of 1988-1995 and the published materials (196
1-1985) are analysed. Dominance of females in the population is shown
to depend on their age; the sex ratio for the investigated period did
not change significantly, the portion of females being reduced somewha
t in the 90s. There were no actual variations in the age structure, th
ough a tendency towards increasing order animals by the late 80s was o
bserved. The reproductive potential was kept low by the late 80s (late
maturing of females, 30% of dry adult females and oth.) and related t
o the epizooty of 1987/1988. Recently the situation has changed for th
e better: in the 90s 4-5-year-old females gave birth to 11% of all cub
s (70% of the seals were dry), the percentage of dry mature females re
duced to 17-20%, the older females, which are maximum fertile, made th
e greatest contribution to the population numbers, the average age of
their being 6-7 years.