S2: BIO Topic Session (1 day)
Mechanisms that regulate North Pacific ecosystems: Bottom up, top down, or something else?
Co-Convenors: Douglas DeMaster, George L. Hunt, Jr. (U.S.A.), Michio J. Kishi (Japan), Jeffrey M. Napp (U.S.A.) and Andrew Trites (Canada)
Within the PICES region, dramatic changes have
been observed in the past 50 years in the structure and function
of marine ecosystems. In an effort to understand what caused these
changes, various hypotheses have been proposed as controlling mechanisms
for entire ecosystems or for particular components of the ecosystems
(e.g. fish stocks and apex predators). Each of the hypotheses
(e.g., Trophic Cascade, Oscillating Control, Nutritional
Stress and Regime Shift), has at its core, a fundamental assumption
that control is the result of bottom-up, top-down, or a wasp waist
trophic pyramid restriction. Is it really that simple? Are these
hypotheses testable? Will they lead us to a predictive capability?
This session will critically examine these hypotheses, as applied
to ecosystems and important marine populations from the western
and eastern North Pacific Ocean. The goal is to review, based on
observations and model results, the basic assumption (source of
control), and to evaluate the strength and weaknesses of the individual
hypotheses. The session will also discuss how the different control
mechanisms might affect the ability of managers to maintain sustainable
fisheries in the region. The possibility of publishing the results
in a special issue of a leading international journal will be explored.