96 ALASKA FISHERIES AND FUR INDUSTRIES IN 1918. 
The records of these branded seals are of very great importance, 
because they show the range of variation in the size of each age class. 
There has not been found any single external characteristic which 
can be relied upon absolutely for the differentiation of one age from 
that above or below it. e weighing of theskin is very unreliable 
as an indication of age, as the weight varies according to the condition 
of each animal and the manner in which the skin is removed from 
the carcass. The weight of animals in any class is likewise subject 
to great variation, depending entirely upon their physical condition 
when killed. The length of the body from the tip of the nose to the 
base of the tail also varies; there is an overlapping in this respect of 
any three consecutive age classes. A sufficient number of the 
branded animals of each age up to 6 years have been killed, how- 
ever, to show the extremes of length of the majority of each class. 
It is reasonable to assume that the remainder of iis herd is subject 
to the same variations as the branded animals, so that when these 
points separating the several ages are found for the latter they can 
be ee standards for the classification of all animals which may 
be killed. 
Owing to the fact that the seals obtain a considerable part of their 
growth during the summer season, the lengths in summer are not 
applicable to animals which may be killed in the fall; the number of 
branded animals, however, which have been killed in the fall is not 
sufficient to make the results of computations based on them entirely 
satisfactory. Such information as there is leads to the belief that 
the addition of 2 inches to the maximum and minimum lengths as 
found for summer seals is sufficiently accurate for the segregation of 
those taken in the fall. The fall killings are small anyway, being 
made largely in order to provide food for the natives for winter, and 
are insignificant In comparison with the total number killed. 
The following table chow the measurements which will be used 
in making the age classification of all seals killed in 1919: 
AGE STANDARDS OF Bopy LenetuHs oF Fur SEALS. 


Lengths of Lengths of 


Age. summer seals. fall seals. 
Inches. + Inches. 
WiOATHNGe. tose eas ase ee on eee Pe Sel eS We eee ac Weise seeeee Up to 36.75 Up to 38.75 
2-V@ar-OldS! coe 2 )-- ete nee Tee SR ee ak, Ue ate Sakl Wieiedy I sah 37 to 40.75 39 to 42.75 
3-year-olds.....-.. bee hic Sie te MO mR ee ane are Acore eras cS em aoe 41 to 45.75 43 to 47.75 
A-YVORD-OlUS S21. 02 ae al faces trees pene c ie Reine a Coe eae eee rcce ee 46 to 51.75 48 to 53.75 
5-year-olds. ...- Sep Ee a eee lee eel te SEs aol ao eee ae aS He ee Beds = sci 52 to 57.75 54 to 59.75 
6-year-oldse: <2... aa5-t Po pede cic ee SE MES SO ee emesis paws 58 to 63.75 60 to 65.75 

AGE CLASSIFICATION OF SEALS KILLED. 
Whenever seals are killed on the Pribilof Islands the lengths are 
taken by means of a pair of beam calipers. These records enable the 
age classification by comparison with the standards derived from the 
measurements of branded animals of known age. This work is highly 
important because it enables for the first time the securing of definite 
information regarding the number of animals in a particular age class, 
and any required reserves can thus be determined with accuracy. 
