FUR SEAL INVESTIGATIONS, 1966 



by 



Bureau of Commercial Fisheries 



Marine Mammal Biological Laboratory 



Sand Point Naval Air Station 



Seattle, Washington 98115 



ABSTRACT 



In 1966, 52,497 nnale and 391 female fur seals ( Callorhinus ursinus ) were killed 

 on the Pribilof Islands. 



Counts of dead fur seals included Z7,392 pups, 222 adult males, and 227 adult 

 fennales . 



Malnutrition, hookworm disease, infections, and bite ■wounds were the major 

 causes of death of 164 pups examined in 1966. 



On the Pribilof Islands 9,948 harem and 6,856 idle males were counted in 1966. 



Of the 51 4-year-old females examined, one was primiparous and post partum; 

 none of the 65 3-year-old females had been gravid. 



Handling apparently causes pups to lose weight or slows their rate of weight 

 gain. 



A total of 12,499 pups were tagged and checkmarked and 12,077 were marked. 

 Two tags were attached to 2,978 males older than pups on St. Paul Island. Recoveries 

 of seals marked in previous years included 4,418 marked as pups and 159 marked 

 at age 1 or older on the Pribilof Islands, and 30 seals marked as pups on the Soviet 

 Islands. 



Pups tagged in late September apparently survive the effects of tagging better 

 than pups tagged in mid-August. On the basis of tag recoveries, the estimated 

 number of pups born decreased steadily from 643,000 in I960 to 440,000 in 1964. 

 The estimate of pups born in 1966 from marked-to-unmarked ratios was 380,000. 

 Estimates from marked-to-unmarked ratios were similar to total counts of pups 

 on three rookeries. 



An estimated 78,000 males from each of two year classes (1961 and 1962) 

 survived to age 1. 



The forecasted kill of 3- and 4-year old male seals on St. Paul Island in 1966 

 was 40,000; the actual kill was 37,669. The forcasted kill of males on the Pribilof 

 Islands in 1967 includes 4,000 of ages 2 and 5, 34,300 of age 3, and 17,900 of age 4. 



The 249 adult males killed for study and the 157 adult males found dead had 

 similar age distributions. The annual replacement rate for males age 10 and older 

 is estimated as 0.38. 



Sixty-six genital tracts from adult females were collected from 13 September 

 to 28 November. The first of 17 tracts with implantation chambers was collected 

 4 November; all 5 tracts taken on 28 November had implantation chambers. 



In a test to determine accuracy in assigning the correct ages to fur seals from 

 canine teeth, the lowest errors were 2.5 to 3.9 percent for males in ages 2 to 5 and 

 3.8 to 21.3 percent for females in ages 3 to 7. Japanese and U.S. readers disagreed 

 on 18.2 percent of males in ages 1 to 4 and 36.5 percent of females in ages 1 to 7 

 in two other groups of teeth. 



Succinylcholine apparently is unsafe for use in immobilizing adult male fur 

 seals. 



Seal pups gained more weight when fed calciunn caseinate and fish flour than 

 when fed fish flour alone. Colostrum milk obtained immediately post partum has 

 much higher levels of albumin and globulin than does milk of later lactation. 



