Table A. — Pelagic tag recovery rates, 1958-63 



Table 5. --Tag recoveries from fur seals collected by U.S. research 

 vessels in Bering Sea in 1963 



Includes H numbers 1-10,000, no series letter numbers 10,001-50,000. 



longer than nonpregnant fur seals of the same 

 ages was first noted by Taylor, Fujinaga, and 

 Wilke (1955). Differences, which are nnost 

 noticeable in seals under 10 years of age, 

 have been observed in the pelagic collections 

 from 1958 through 1963. In early comparisons, 

 post partum seals were included with pregnant 

 seals. In 1962, however, the mean lengths of 

 548 post partum females were compared with 

 the mean lengths of 282 pregnant and 513 

 nonpregnant females (Fiscus, Baines, and 

 Wilke, 1964). The data showed that the lengths 

 of post partum females agreed more closely 

 with the lengths of nonpregnant females, rather 

 than with the lengths of pregnant females as 

 would be expected. In 1963, mean lengths of 

 4,074 pregnant, 1,528 post partum, and 2,353 

 nonpregnant females collected from 1958 

 through 1963 in eastern Pacific waters were 

 compared (fig. 3). As in 1962, the lengths of 

 nonpregnant and post partum seals agreed 

 more closely than did the lengths of pregnant 



and post partum seals. Considering the sample 

 size, it is doubtful that measurement errors 

 could account for this result. For an unknown 

 reason, pregnant females apparently decrease 

 in length after parturition. We are not aware 

 of physiological changes in mammals that 

 would account for the increased lengths of 

 the pregnant seals. 



Tables 15 and 16, appendix A, give the mean 

 lengths and weights of fetuses collected from 

 1958 through 1963. The average weight and 

 length of fetuses by 10-day periods are plotted 

 in figures 4 and 5. Information is lacking for 

 November and December, an important period 

 because it is the time when the blastocyst is 

 implanted. 



Pregnancy rate . --The pregnancy rates of 

 female seals collected from 1958 through 1963 

 are shown in table 6. Approximately 36 

 percent of the 5-year-old primiparous females 

 collected in 1963 were pregnant from con- 



