Subject: abstract -role of pinnipeds in ecosystem (fwd)

Mike Williamson (
Fri, 24 Apr 1998 13:49:19 -0400 (EDT)

---------- Forwarded message ----------
Date: Wed, 22 Apr 1998 16:31:50 -0700
From: Stella Ceeline <>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: abstract -role of pinnipeds in ecosystem

Attached is an abstract from a recently published paper that might
interest MarMam readers.  Please direct reprint requests to:

Trites, A.W. 1997. The role of pinnipeds in the ecosystem. In Pinniped
populations, eastern north Pacific: status, trends and issues.  Eds. G.
Stone, J. Goebel and S. Webster.  Pages 31-39. A symposium of the 127th
Annual Meeting of the American Fisheries Society.  New England Aquarium,
Conservation Department, Central Wharf, Boston, MA 02110.

Abstract: The proximate role played by seals and sea lions is obvious:
they are predators and consumers of fish and invertebrates.  Less
intuitive is their ultimate role (dynamic and structural) within the
ecosystem.  The limited information available suggests that some
pinnipeds perform a dynamic role by transferring nutrients and energy, or
by regulating the abundance of other species.  Others may play a
structural role by influencing the physical complexity of their
environment; or they may synthesize the marine environment and serve as
indicators of ecosystem change.  Field observations suggest the ultimate
role that pinnipeds fill is species specific and a function of the type
of habitat and ecosystem they occupy.  Their functional and structural
roles appear to be most evident in simple short-chained food webs, and
are least obvious and tractable in complex long-chained food webs due
perhaps to high variability in the recruitment of fish or nonlinear
interactions and responses of predators and prey.  The impact of historic
removals of whales, sea otters and seals are consistent with these
observations.  Many of these removals produced unexpected changes in
other components of the ecosystem.  Better insights into the role that
pinnipeds play and the effect of removing them will come as better data
on diets and predator-prey functional responses are included in ecosystem