FISHERY BULLETIN: VOL. 84, NO. 2 



suggested that the largest number of yearlings of 

 unspecified sex was present on 27 September to 11 

 October. These animals were predominantly males, 

 as indicated by the recorded sex ratio of 84% males 

 in a sample of 356 yearlings seen during 1961-65 

 (Roppel et al. 1965a, 1965b, 1966). Osgood et al. 

 (1915) noted all yearlings examined during his study 

 were males. Surveys by Abegglen et al. (1961) in- 

 dicated very few yearlings of either sex were pres- 

 ent on rookeries after early November. 



^7-Year-Olds 



Essentially all males present on rookeries during 

 the pupping season were bulls (Jordan and Clark 

 1898). According to Johnson (1968), the age of such 

 bulls would have been >1 yr. Peterson (1965, 1968) 

 noted that bulls began to arrive on rookeries in mid- 

 May, reached peak numbers by late June, and 

 declined in numbers after mid-July. No data exist 

 on whether old bulls arrived before young bulls. 



(Lander 1981). Pregnant females age ^4 were rarely 

 taken on hauling grounds during July, but were in- 

 creasingly common during 1-15 August (Fig. 3). 

 Using the trend in the number of 4- and 5-yr-olds 

 killed after 15 August, most pregnant females prob- 

 ably arrived by mid-August. Because essentially all 

 pregnant females gave birth in July, the pregnant 

 females killed on hauling grounds during August 

 would have been postpartum. An examination of the 

 median dates for collection of pregnant females sug- 

 gested that arrival times on hauling grounds of age 

 ^4 did not differ among ages (Table 2). 



Nonpregnant 



1-YEAR-OLDS.— As with yearling males, year- 

 ling females apparently preferred rookeries to haul- 

 ing grounds (Jordan and Clark 1898; Roppel et al. 

 1965a). No yearling females were taken on hauling 

 grounds during the commercial kill for females up 

 to 20 August. 



Arrival of Females on Hauling Grounds 



Pregnant, >4 Years 



Very few females younger than 4 yr give birth 



2000 



1000 



II 16 21 26 31 

 JULY 



5 10 15 20 



AUGUST 



Figure 3.— Mean number, and range, of pregnant females of 

 northern fur seal killed of age >4 on hauling grounds of St. Paul 

 Island, by date. Data from Lander (1980) and annual reports of 

 the National Marine Mammal Laboratory, Seattle. 



2-YEAR-OLDS.-Jordon and Clark (1898) and 

 Osgood et al. (1915) suggested 2-yr-old females also 

 preferred rookeries to hauling grounds. However, 

 a few were taken on the hauling grounds during the 

 harvest for females. Numbers began to increase in 

 mid- August (Fig. 4), and thus increases began about 

 1 mo later than males of the same age. Assuming 

 a 1-1 V2 mo interval for essentially all animals to ar- 

 rive, as assumed for 2-yr-old males, then 2-yr-old 

 females probably arrived by mid- to late Septem- 

 ber. 



^3-YEAR-0LDS.-Very few nonpregnant fe- 

 males >3 yr were taken on hauling grounds in July, 

 but many were present by 15 August (Figs. 4, 5). 

 Based on the trend in the number of females killed 

 at 3-5 yr, the arrival of ages >S yr was essentially 

 completed by mid-August. Support for this conclu- 

 sion comes from Peterson (1965, 1968), who counted 



Table 2.— Median dates of collection of pregnant and nonpregnant females of north- 

 ern fur seals taken during 1956, 1958, and 1959 on hauling grounds of St. Paul Island. 

 All dates are in August. Data from annual reports of the National Marine Mammal 

 Laborabory, National Marine Fisheries Service, NOAA, Seattle. 



388 



