Table 15. --Summary-'- of tag loss for male seals 

 tagged at age 1 or older, Pribilof Islands, 

 Alaska 



Table 16. — Tag recoveries from male seals tagged as pups in 

 August and September, St. Paul Island, 1963-6^^ 



Tag 

 series 



Time 

 elapsed 



since 

 tagging 



Both tags 

 recovered 



One 

 tag 

 lost 



Incidence 

 of tag 



loss 



Years Number Number 



2S 1 320 399 0.38 



2S 2 _45 _63 0.^1 



Total. 365 462 0.39 



2T 1 404 30 0.04 



IR 1 35 21 0.23 



IR 2 105 113 0.35 



IR 3 _31 _35_ 0.36 



Total. 171 169 0.33 



IS 1 77 51 0.25 



IS 2 132 150 0.36 



Total. 209 201 0.32 



IT 1 84 7 0.04 



■"■ Seals known to have lost two tags were 

 excluded because there was no way to determine 

 the tag series that had been applied. 



returns were slightly higher among those with 

 a tag and a checkmark (100) than those with 

 an RHl mark (72) or an RFV mark (94). In 

 1968, however, only 588 males were recovered 

 with tags and checkmarks compared to 67 3 with 

 RHl marks and 709 with RFV marks. The small 

 difference between the groups that received 

 RHl and RFV marks was not significant 

 (P = 0.4), but the difference between these two 

 groups and the group given tags and check- 

 marks was significant (P<0.005). 



Of the seals marked in 1966, fewer Z-year- 

 old males killed in 1968 had marks only 

 than had tags and checkmarks (table A- 32). 

 This condition was also true for animals 

 marked in 1965 and recovered in 1967. 



We tentatively conclude that pups given 

 marks have a higher survival rate than those 

 given tags and checkmarks. The rate of re- 

 covery for males given a mark in 1965 and 

 recovered at age 3 in 1968 was 1.17 times 

 that of animals given a tag and checkmark. 

 A higher recovery rate for males given a tag 

 and checkmark and killed at age 2 in 1967 is 

 attributed to unintentional selection for tagged 

 animals during the kill. Most of the 2-year- 

 old males are shorter than the minimum body 

 length limit of 42 inches (107 cm.)setfor kill- 

 ing. It is probable that among animals near 

 this minimum limit, the people responsible for 

 killing the seals select more tagged animals 

 than those not visibly marked. If true, selec- 

 tion for tags by these people is undoubtedly 

 subconscious and exaggerated because a seal 

 with a tag attached to its flipper is more 

 conspicuous than a seal with only a mark. There 

 should be little or no selection for tagged 

 animals among 3-year-old males because 

 very few seals of this age are shorter than 

 the minimum body length limit of 42 inches 

 (107 cm.) set for killing. Selection for tagged 

 animals is discussed further in the section 

 on population estimates. 



POPULATION ESTIMATES 



We are currently evaluating each year 

 class of seals by making estimates of its 

 size at three stages of life: (1) Number of 

 pups born; (2) number of pups that survive 

 to age 1; and (3) number of the year class that 

 survive to age ;l- 2. The estimates are pre- 

 sented in this section. 



Because the age composition of 1,333 males 

 killed after 2 August was not determined, only 

 the recovery data collected before 3 August 

 are used in calculations based also on the 

 number of male seals killed. 



NUMBER OF SEAL PUPS BORN 



vVe make estimates of the number of pups 

 born from: (1) tags and marks applied to pups 

 of both sexes and recovered when the animals 

 are taken in the kill; (2) shearing and sampling 

 of pups; and (3) complete counts of living pups 

 on some rookeries. The first method was used 

 to estimate the size of year classes 1962-66 

 and the last two were used to estimate the nun-i- 

 ber of pups born in 1968. In making estimates 

 of the number of pups from tags and marks, we 



16 



