Subject: abstract - Steller sea lions (fwd)

Michael Williamson (
Thu, 1 May 1997 09:52:52 -0400 (EDT)

J. Michael Williamson
   Principal Investigator-WhaleNet <>
   Associate Professor-Science
   Wheelock College, 200 The Riverway, Boston, MA 02215
voice: 617.734.5200, ext. 256
fax:    617.734.8666, or 617.566.7369

---------- Forwarded message ----------
Date: Wed, 30 Apr 1997 08:23:06 -0400
From: Dagmar Fertl <>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: abstract - Steller sea lions

     On behalf of a request made by the Marmam editors, I am posting
     abstracts for the lastest issue of Marine Mammal Science.  This is
     being cross-posted as well to the ECS mailbase.  I have included the
     mailing address of the author to whom inquiries should be directed,
     please do not send the mail to me.

     Westlake, R.L., W.L. Perryman, and K.A. Ono.  1997.  Comparison of
     vertical aerial photographic and ground censuses of Steller sea lions
     at Ano Nuevo Island, July 1990-1993.  Marine Mammal Science 13(2):

     National Marine Fisheries Service, Southwest Fisheries Science Center,
     8604 La Jolla Shores Dr., La Jolla, California 92038

     Counts of Steller sea lion (_Eumetopias jubatus_) pups and non-pups
     (adults and juveniles) from aerial photographs of rookeries at Ano
     Nuevo Island between 1990 and 1993 were significantly higher than
     those made on the ground.  Based on regression of natural logs of
     photographic counts versus year, the number of pups declined at a rate
     of -0.099/yr while non-pup numbers declined at -0.315/yr.  Examination
     of ground count data for the same period revealed a significant
     decline in non-pups (-0.139/yr), but no trend was detected in the
     ground count of pups.  The regression coefficients from photographic
     and ground counts of non-pups did not differ significantly.  Power
     analyses using the program TRENDS indicated that detectable rates of
     change in abundance from four annual surveys were much lower for
     counts of pups than counts of non-pups where sampling precision was
     based on fits to linear models.