118 ALASKA FISHERIES AND FUR INDUSTRIES IN 1918. 
The percentage of increase in the number of pups on a given rookery 
is dependent upon the choosing of a landing place by the cows. 
Accordingly great variations in the percentage of gain on individual 
rookeries have been recorded during the past few years. Thus in 
1918 one rookery on which a count was made gained 154 per cent, 
while another lost 3 per cent. There is no adequate explanation 
available for these conditions. The gains for the entire herd, how- 
ever, seem to be following closely an autocatylitic curve, as was 
pointed out by Prof. G. H. Parker. During the past six years the 
percentages of increase have been 12.54, 1.06, 11.02, 12.99, 9.44, and 
11.63, with an average of 9.78 since 1912. For a rough calculation 
into the future it may be placed at 10 per cent, and taking into 
consideration the conservative errors of the census it may actually 
exceed this figure through a period of years. 
PERCENTAGE OF INCREASE OR DECREASE IN THE NUMBER OF Pups IN 1918 From 1917. 
a 
Percentage 
Total Total F 
Rookery. pups, pups, Corde 
1917. 1918. Iorease (—). 
ST, PAUL ISLAND. 
2,520 2,540 + 0.79 
2, 235 90935 Nn ae ee 
8, 649 9, 486 + 9.67 
726 792 + 9.09 
17, 442 19,398 + 11.21 
, 060 6,3 + 25.00 
466 512 + 9.87 
15, 433 16, 725 + 8.37 
9, 828 11, 460 + 16.60 
e aes i , 86: 9,089 + 32.43 
Zapadni Reef... 358 536 + 49.72 
Polovindior <sasesena isco ae < gst 28 at eee eo ee ee oe 4,918 5, 343 + 8.64 
Poloyins Cliffe. oe once cnc he Powe een eee ane eae 1,761 1, 882 + 6.87 
LaittlesPolovands:2 22 45. Boe ee eee eee ee ae 1, 260 1,491 + 18.33 
MGV OV oe sae rt ce eee eee ee a acee eee 2,921 3,335 + 14.17 
WVastochni£25. 55 At.8 5 oder tanec eee Cee tenes aoe hee 28, 249 31, 468 + 11.39 
"POU 2 So San Soe Satan cto eee Coe a EOE RE ec ec ates See 108, 689 122, 617 + 12.81 
ST. GEORGE ISLAND, 
NODE os = <b cea ine otto cl cee Saha oe eee meee ne eee 6, 783 7,011 + 3.36 
Staraya Artil 5, 642 5, 440 — 3.58 
YAY 1:6 bat meen ae a | Rea | ae 1,050 806 — 2.32 
Somthets Fe ee. rd oe 24 61 +154. 16 
Basti Reel: fs" ys2- ie oe 1, 786 2,120 + 13.70 
WastOlits Sea god aoe as cn coche ee aeons ae eee eee 4,050 4, 860 + 20.00 
Total! Sst 5 ce 8s jt ici encgee sane Band one ae eee ae 19, 335 20, 298 + 4.98 
Total; bothislands ses (eee ag tees = So heet eee eee 128, 024 142,915 + 11.63 
BREEDING COWS. 
By inference the number of breeding cows is the same as the 
number of pups, 142,915. This is a very creditable increase of 
14,891, or 11.63 per cent from 1917. The increase showed very 
materially on the rookeries. Many of the avenues left for ingress 
and egress to the hauling grounds have closed up or are fast closing. 
Small outlying breeding masses of seals are being joined to larger 
masses and there is a general ene rearward. The season was 
marked by the establishment of very few new breeding sections. 
«Proceedings, National Academy of Science, vol. 4, p. 169. 
