Using Me Ecopam N Approach to Assess Krll.l Biomass and 1996. Structuring Models for Dynamics of Exploited Ecosystems from Trophic Mass-balance Assessments. (ms)

[Following the workshop where the above was presented, Dr Carl Walters of the Fisheries Centre, UBC, developed an approach now implemented as an ECOPATH II subroutine called ECOSIM, which reexpresses the linear equation system that the ECOPATH approach relies on, into a system of differential equations which can be integrated over time (Walters et aI1996). Thus, once an ECOPATH II model is constructed, its outputs can be used to run, without further input, a simulation model of the system in question; perturbations can be studied (by changing the temporal pattern of fishery mortality, e.g. on krill predators) and the temporal responses (e.g. of krill) studied. Preliminary examination with ECOSIM, of the dynamics of 50+ of the ecosystems so far described with ECOP A TH II was found to be useful in characterizing the key role of prey species (such as krill) in ecosystems, thus providing additional reasons for recommending the modeling approach suggested above.] Daniel Pauly, Fisheries Centre UBC and ICLARM