A model lying between the two extremes in complexity is presented here. It 

 is a simplification of the extensive biomass-based models of Laevastu and Larkins 

 (1981) without spatial resolution. The formulae used in this model correspond to 

 those of the larger models (DYNUMES and PROBUB) and are characterized by their 

 straightforward relationship to the available data. Unknown parameters and 

 coefficients for which there are little or no data are kept to a minimum. In 

 general, the formulae are of a linear form, in the absence of any biologic 

 information to the contrary. 



Abbreviated ecosystem models are an aid in evaluating the relative importance 

 of component processes in the ecosystem. They have the advantage of being readily 

 assimilable by both the modellers and their audience, but they are a simplification, 

 Lack of spatial heterogeneity and a lack of recruit variability in particular, 

 limit the results to average solutions. Their purpose is not to attempt to define 

 the ecosystem and its processes, but rather to foster an understanding of the 

 general interactive processes. 



This paper presents the formulae used in the model, followed by a more detailed 

 examination of the interactive processes in the feeding routines. The reader is 

 referred to Laevastu and Larkins (I98I) for a comprehensive discussion of the 

 attributes of biomass-based models in general. It is stressed that the formulae 

 presented herein are not invariable, but should be changed to reflect available 

 information on the species under consideration or the beliefs or hypotheses of 

 the researcher. Sample input data and parameters are presented in the following 

 sections, together with results from this preliminary modelling. The species 

 composition has a rough correspondence with that of Georges Bank, but the data 

 do not necessarily correspond to published data. 



