106 U. S. BUREAU OF FISHERIES. 
INCREASE OR DECREASE IN NUMBER OF PUPS IN 1920 FRom 1919. 
- one 
umerical +) or 
Rookery. Total pups, Total Pups, aGronaek dacrasse 
ST, PAUL ISLAND. 
a Per cent. 
IY 757 Bape ee REE Ls RE ge eter ote Sd Oto 3, 565 3, 764 199 + 5.58 
Tutiteanince ee CA ees sue) ea eae ae, ee 2° 788 2) 932 144 + 5.16 
Garbathns Mapes. ve’ Ga eee cen 12? 308 10,251 |  —2,057 —16.65 
HAUG WED les Sesh} a eee ante Sete ane Bigs Ds Eee ie 1,150 1, 180 30 + 2.61 
Recisesvine tic iaw. 01 4.0. Sauipe mnie 22 457 23) 638 1,181 + 5.26 
Sigil eee en ce ae i ee ee 7, 015 8,375 1, 360 +19. 39 
Mabon, Se Gr ania s \ Ar eRe Spence acme ee ame 1445 tga 1) yoy —23.37 
POIs An ee We kee Te Wed eee eee aa 16, 027 17,286 1,259| 2786 
Tait i an a oe MR AD Re REO LI SON! Cael Sa 14,300 16,399 27099} +14.68 
Isiftle Zapadnit.)o..eos a8 SOO Ne UTS EEN 10) 145 12) 494 2) 349 423.15 
ZapadmnisRest a io sk onl eau sae an a megs 1 604 1530'| 9 70) eerie 
Bayes Sg emNn ay Meme NECN ED: (iG were e, 15, 794 16, 006 212 + 3.66 
Palovane) Clitis 0: "hc Nyc NOk Ubtia 2 elena eae 127209 12) 573 364| +16.48 
Higete Polowinia Se cae ees ee epee a 1, 203 1,711 508 +42.23 
Morons e226 esa e hate She ee ak aw i be! Sar O41 12'936| . —. 105 bi) Gees 
Mostochnign | (0: arte rcells wary an ie eee a Se | 30, 863 32? 857 1,994; + 6.46 
Sey eye ARM, Dieegan em PONY Teh eure ta ese Ls eS Dae 133,914} 143,275 9,361; + 6.99 
| 
8, 802 9, 126 324| + :3.68 
15, 746 5, 944 198)| 1) sepa 
1857 1907 50 + 5.83 
1 68 199 31| . +45.59 
1 2,367 12,571 204/44 8.62 
5,418 5, 605 137 + 3.45 
23, 258 | 24, 252 994 4+ 4.27 
Total vbothisiands:.0 fo... ak Wh oe_ aehasnyaes 157,172| 167,527 10, 355 + 6.59 
} 
1Pups counted. 
It will be noted that upon some of the eight rookeries counted there 
has been no gain, whereas on others it has been considerable, and 
again that the gain on the lot has been only 3.77 per cent. This latter 
fact indicates very strongly that the gain of breeding cows has not 
been the 9 per cent which has been considered to be the normal rate. 
Tt is true that the smaller rookeries do not increase as rapidly as 
the large ones, but there should not be this much discrepancy even 
though | it is possible. It is entirely possible for the rookeries counted 
to have lost and the herd as a whole gain the normal amount, but it 
is not probable. The abnormal gain on the other rookeries would 
have been a noteworthy feature to a person who had had them in 
view during successive years. After a consideration of all of the 
factors which enter into the problem, the gains on the several rook- 
eries have been estimated as shown in the above table. This, of 
course, is made up largely from the data on average harems (p. 116). 
It shows the gain of pups (and breeding cows) for the entire herd 
to be 6.59 per cent. 
A noteworthy feature of the rookeries on which counts were made 
is the actual decrease in the number as well as the percentage of pups 
found dead in spite of an actual increase of total pups. This is entirely 
in accordance with predictions as to what would happen when the 
size of the harem would be increased. By using the figures of dead 
pups found on the various rookeries the numbers have been esti- 
mated for those which were not counted. This is shown in the table 
