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Fur Seal Investigations, 1970
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1971
[PDF-34.23 MB]
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Description:Data was collected on the Pribilof Islands and at sea within the period March to October 1970. In 1970, a kill of 53,700 male seals was forecasted; the actual kill included 42,121 males and 120 females. Counts of living adult males were 9, 035 in June and 9, 354 in July. Counts of dead fur seals included 25, 040 pups and 233 animals older than pups. The main causes of death among 221 pups were hookworm disease, malnutrition, infection, trauma, and perinatal complex. Male pup weights averaged 10.2 kg and females 9. 0 kg. We marked 25, 919 pups of both sexes and 3,779 male seals of ages 1-4 years, and recovered 3,473 marked male seals. Tag loss varies with tag series and for some appears to increase with age; apparently tagged animals suffer greater mortality than untagged seals. The pup population in 1966 was estimated at 437,000 from one method and 388,000 from another; an estimated 306,000 pups were born in 1970. Estimates of the survival of males from the 1966 year class to age 1 and 2 yielded 102,232 and 57,826, respectively. Of 1,886 seals sighted off Washington, 403 were collected, 78 were wounded and lost, and 67 were killed and lost. Single seals were sighted more frequently than were groups of 2 or more. Twenty yearling seals from the 1969 year das s were taken and 67 percent of 368 female seals killed were from 1 to 7 years old. Nineteen marked female seals were collected. Thirty-three percent of the nonpregnant female seals in ages 4 to 21 years apparently had ovulated. Squids were the leading food species consumed by fur seals in 299 stomachs containing food. Northern anchovy, rockfish, salmonids, and Pacific herring followed in importance. Salmon were the most valuable commercial fish eaten by fur seals off Washington.
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