Environmental Engineering Reference
In-Depth Information
model groups (diatoms, dinoflagellates and myctophic fish) were fixed during the
model runs. As shown by the figure, anchovy dynamics are well simulated. The
initial decrease in anchovy biomass during 1997-1998 is mainly reproduced by
forcing phytoplankton abundance downwards; specifically, a decrease in diatom
biomass and subsequently, a decrease in the second most important food item,
mesozooplankton.
The application of fishing as an external driver improved the fit of the simulation
and helped to explain the long-term dynamics of several main target species. The
fishing driver decreased long-term variance by 22% (Fig.
5.4
) pointing to the
important role of fishery in shaping the trophic flows and biomass distribution in
the system.
5.4 Outlook
Through the integration of the biomass budget (balanced flows) approach of
Ecopath with the time-dynamic approach of Ecosim, a modelling software package
(EwE) was created, which can be used for a great variety of data situations and
purposes. In the most data sparse situation, Ecopath can be used to integrate
available biological, ecological and fisheries information of the ecosystem to obtain
a first holistic view and understanding of the system under study. The process of
model construction is most instructive since questions of ecosystem functioning
and process rates are addressed. Since model construction requires the knowledge
input of different experts (for the different model groups studied), the process of
model construction may help to integrate groups of researchers working in the same
Table 5.2 Further application examples using the EwE-software
Application
EwE
package
Author(s)
Comparison across ecosystems
Ecopath Christiansen and Pauly (1993),
Moloney et al. (2005)
Comparison of ecosystem states
Ecopath
Shannon et al. (2003), Tam et al.
(2008), Taylor et al. (2008c), Wolff
(2006)
Ecosystem phase shift exploration
Ecosim Shannon et al. (2004)
Optimal harvest strategies
Ecosim Arregu´n-S´nchez et al. (2004a, b)
Mediation of trophic controls with actual
environmental time series
Ecosim Field et al. (2006)
Mediation of trophic controls by a third
functional group
Ecosim Guenette et al. (2008)
Fitting of trophic mediation time series with
post-hoc comparison to actual time series
Ecosim Shannon et al. (2008), Coll et al. (2009)
Exploration of trophic and environmental
drivers
Ecosim Taylor et al. (2008a-c)
Marine protected area exploration
Ecospace Okey et al. (2004)
