Table 24-. — Estimates of the number of yearling male seals, year classes 

 1964--66, from recoveries of tagged male seals, Pribilof Islands, Alaska 



1964 

 IR 

 IR 

 IR 

 IR 



1965 

 IS 

 IS 

 IS 



Years 



815 



1, 277 



1966 

 IT 



1968 



2, 040 



709 



75 



19, 285 



l/ Number of tags applied were adjusted according to the error in age 

 determination at time of tagging as observed when tagged animals were 

 recovered in the kill. Data for the 1965 year class were used to adjust 

 the number of tags applied to the 1966 year class. The number for 1965 

 was further adjusted by dividing 1.08 to account for recoveries expected 

 in 1969. This adjustment was based on the average ratio of error in de- 

 termining age for 3 -year -olds through the kill, and all recoveries for 

 the 1961, 1962, and 196-4 year classes. 



2/ The adjusted total includes animals recovered but for which data 

 are missing, those of unknown age, and double-tag loss. The proportion 

 in each age within a tag series was used to allocate animals of unknown 

 age that could be identified as belonging to a given tag series; seals 

 that lost both tags and could not be identified as to the year tagged 

 were allocated according to the number of tags recovered for each age 

 and tag series (see example in section of Number of Yearling Male 

 Seals) . 



each age and tag series. Although this method 

 of allocating the recoveries for which informa- 

 tion is missing is questionable, there is some 

 advantage in including the data. We hope to 

 devise a better method when seals with tags 

 of the series involved have been killed at ages 

 through 5 years. 



Estimates of the number of yearling males 

 vary considerably from one year class to 

 another and between years within a year class. 

 Estimates of the number of yearling males 

 from all recoveries for year classes 1961, 

 1962, 1964, and 1965 were 82,000, 79,000, 

 115,000, and 80,000 respectively. The estimate 

 for each of these year classes from recoveries 

 at age 2 was miuch lower than estimates from 

 recoveries at other ages, a condition that could 

 have been caused by selection for tagged ani- 

 nnals during the kill. If the estimates from re- 

 coveries at age 3 are correct, we recovered 



more than twice the expected number of tagged 

 anin-ials at age 2 from year classes 1964 and 

 1965, and also from year classes 1961 and 1962 

 (Marine Mammal Biological Laboratory, 1970). 



NUMBER OF MALE SEALS AGE 2 YEARS 



Males known or believed to be 2 years old 

 were tagged in 1966, 1967, and 1968 (age was 

 subsequently determined from the canine teeth 

 of these seals--some of the animals were 

 actually ages 1, 3, and 4 when tagged). Seals 

 tagged in 1966 have nowbeen harvested through 

 two seasons, and few additional recoveries are 

 expected. Age was determined from canine 

 teeth for all seals from this group as they 

 appeared in the kill, except those from which 

 the head or flippers were tornfromthe carcass 

 during the skinning process. The age distribu- 

 tion of the tagged animals was then used to 



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