Subject: abstract - population dynamics of fur seals (fwd)

Michael Williamson (
Thu, 1 May 1997 09:52:24 -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 08:44:18 -0400
From: Dagmar Fertl <>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: abstract - population dynamics of fur seals

     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.


     Wickens, P. and A.E. York.  1997.  Comparative population dynamics of
     fur seals.  Marine Mammal Science 13(2): 241-292.

     Marine Biology Research Institute, University of Cape Town,
     Rondebosch, 7700, Cape Town, South Africa

     The population sizes, trends, exploitation, and life history
     parameters for the ten fur seal species and subspecies are summarized.
     The largest population is that of _Arctocephalus pusillus pusillus_
     with approximately two million seals, and the smallest if _A.
     townsendi_ with approximately 7,000 individuals.  Most populations are
     legally protected, although controlled harvesting may occur.  None of
     the fur seal populations is currently known to be decreasing.  Data
     are presented for parameters related to the survival of pups,
     juveniles, adults, and territorial males, and to reproduction,
     including the age of attainment of territorial status, aggregation
     sizes, age of first parturition, pregnancy rates, sex ratios of young
     animals, and information on the birth seasons of the different
     species.  Since pinipeds are often of concern in fisheries management,
     their daily consumption rates are of importance, and consequently data
     on body masses are summarized and the paucity fo data on consumption
     rates as a function of body mass noted.  A simplified age-structured
     model is developed, and the results of this model are compared with
     results from more detailed models based on two published life tables
     for _Callorhinus ursinus_.  This comparison shows that the use of the
     simplified age-structured model is justified to explore changes in
     population growth rate.  However, the simplified model does show
     exaggerated age structure effects compared to the more detailed
     models.  This model is used to compare the population dynamics of
     those species for which sufficient data are available.  Areas in which
     limited, or no, data are available for the different fur seal species
     are highlighted.