Subject: abstract - population dynamics of fur seals (fwd)
Michael Williamson (pita@whale.simmons.edu)
Thu, 1 May 1997 09:52:24 -0400 (EDT)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
J. Michael Williamson
Principal Investigator-WhaleNet <http://whale.wheelock.edu>
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
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---------- Forwarded message ----------
Date: Wed, 30 Apr 1997 08:44:18 -0400
From: Dagmar Fertl <Dagmar_Fertl@mms.gov>
Reply-To: Marine Mammals Research and Conservation Discussion
<MARMAM@UVVM.UVIC.CA>
To: MARMAM@UVVM.UVIC.CA
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.
Dagmar.Fertl@mms.gov
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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.