184 



Fishery Bulletin 94(1). 1996 



and topography on the counts obtained by ground 

 and small-vessel surveys. 



Northern elephant seal rookeries at San Miguel 

 and San Nicolas Islands cover many miles of coast- 

 line. Observers counting northern elephant seals on 

 the ground at these rookeries require an entire day 

 or several days to complete a census at just one is- 

 land (Stewart et al., 1994). They have the advantage 

 of being able to spend more time to perform the count, 

 repeat it if necessary, or to determine the sex and 



age class of a seal correctly, but they can cause a great 

 deal of disturbance to elephant seals and pinnipeds 

 sympatric with them (DeMaster et al. 4 ) and their 

 counts lack precision and accuracy. Aerial photo- 



DeMaster, D. P., R. L DeLong, B. S. Steward, P. K. Yochem, 

 and G. A. Antonelis. 1984. A guide to censusing pinnipeds 

 in the Channel Islands National Marine Sanctuary and Chan- 

 nel Islands National Park. Southwest Fisheries Science Cen- 

 ter, Natl. Mar. Fish. Serv.. NOAA, P.O. Box 271. La Jolla. 

 CA. Admin. Rep. LJ-84-44, 22 p. 



