s 
- 10 - 
with those available for the sandspits west of the island gives a figure 
- • 
which compares favorably with censuses made on the island before con¬ 
struction of the facility. 
Calculations performed on the censuses taken since 1956 suggest 
mean populations of 230 (SD 32) for Laysan, 182 (SD 42) for Lisianski, 
and 193 (SD 62) for Pearl and Hermes Reef. The large standard deviations 
reflect the great variability observed in the counts. However, as natality 
and mortality rates are apparently low for this species (see Kenyon and 
w 
Rice, 1959; Rice, 1960; and Wirtz, 1968), and there is little evidence 
for inter-atoll movement, it seems reasonable to accept the high counts 
made during the last ten years as estimates of the adult group utilizing 
these three islands, or 288 for Laysan, 247 for Lisianski, and 286 for 
Pearl and Hermes. 
The mean percentage of tagged seals observed during 70 counts sug¬ 
gests that a very small percentage of the tagged portion of the herd can 
be found on land at any given time. The assumption is made that the tagged 
animals are distributed at random within the population of seals utilizing 
Kure Atoll, and that there is little turnover. If these assumptions are 
met, then, on the average, the number of seals seen on the beach during 
any one census is less than 10 percent of the resident herd. The mean 
number of adult group animals observed for the 70 counts is 25, suggesting 
a total population of 250 adult group seals. Extending this theory to 
counts available for three other islands suggests populations of 2300 
s 
for Laysan, 1820 for Lisianski, and 1930 for Pearl and Hermes. On the 
basis of this calculation the estimate of the world population would be 
