required, then dark nights could 

 slow migration greatly. 



Whales may have some irregular 

 feeding activities, particularly noc- 

 turnal, but no whales migrating in 

 the day were seen feeding off south- 

 ern California. 



The distance from northwestern 

 Bering Sea to San Diego is about 

 6,000 miles. If a little less than 

 three months is postulated as a 

 reasonable time for swimming this 

 distance, and four knots is an aver- 

 age swimming speed, then a gray 

 whale could sleep seven hours in 

 each 24 -hour period. 



On the basis of these suppositions, 

 and lacking accurate information, 

 50 percent of daytime movement 

 was used as an extrapolation for 

 night movement. 



In making extrapolation for night 

 migration, two methods of dividing the 

 day into hours of daylight and dark- 

 ness are evident. The time of sunrise 

 and sunset from late December to 

 mid -February at La JoUa divide the 

 day into 1 to 10-1/2 hours of daylight 

 and 13-1/2 to 14 hours of darkness. 

 If the 7 a. m. to 5 p. m. Point Loma 

 count and the 3 to 5 p. m. Scripps 

 count are added together, the day 

 consists of 12 hours of daylight and 

 12 hours of darkness. A count made 

 on this basis would be 5 to 6 percent 

 greater than if the sunrise-to-sunset 

 division of the day is used because of 

 the lesser movement assumed for night. 

 Compared with other unavoidable in- 

 accuracies in the whale count, this 

 difference is unimportant. For the 

 sake of simplicity, the 50 -percent 

 reduction in nnigratory rate for two 

 hours each day is ignored. 



RESULTS 

 Census of 1952-53 



In general, the weather was good in 

 1952-53 and counts were high. Ehiring 

 this first year, the census method 

 was experimental, although the writer 

 had profited from the experience of 

 Dr. Hubbs. Whales were counted in- 

 termittently at La Jolla from Decem- 

 ber 3-15 and, except for five days, 

 an intensive watch was maintained 

 from December 15 through February 

 15. At Point Lonna, the public whale- 

 watch was intensive only on weekends, 

 December 26 through February 15, and 

 then continued intermittently from Feb- 

 ruary 16 through March 13. 



On this schedule, both crews counted 

 whales (mostly the same individuals) 

 from December 26 through February 

 15. The higher daily count, regardless 

 of locality, was recorded as the value 

 for that day. 



The La Jolla -Scripps post could not 

 be manned for 10 continuous hours 

 every day, even with the help of volun- 

 teers. 



The Point Loma post of the Cabrillo 

 National Monument was never nnanned 

 during the public whale -watch from 

 7 a. m. to 9 a. m., and often not until 

 10 a. m. On week days, it sometimes 

 was not manned at all because of other 

 time demands upon the small, regular 

 staff. Consequently, a 20-percent ad- 

 justment was made in the daily count 

 for the 2 hours out of 1 when whales 

 were not counted. Even when the La 

 Jolla -Scripps count was nearly perfect 

 in coverage and visibility, and ex- 

 ceeded the count at Point Loma, the 

 20-percent extrapolation was neces- 

 sary because the count from 7 a. nn. to 

 9 a. m. at Point Loma represented 

 whales which had passed La Jolla 

 during the night or early morning and 

 could not have been seen there. 



Extrapolation for offshore migra- 

 tion . --As an arbitrary correction for 

 whales traveling offshore, the writer 

 added 5 percent of the total number 

 estimated to have passed San Diego 

 within sight of land. 



Census of 1953-54 



At Point Loma, the National Park 

 Service kept watch for southbound 

 whales when an observer was avail- 

 able and when the part-time watcher 



22 



