L, the loss of nitrogen from the system, and ?2 3, phytoplankton rain, are 

 simple functions of standing stock: 



L = c^Qi and 



p 2,3 = c i,3Q2- 



Rates of predation are donor and recipient controlled and governed by the 

 simple equation 



where 



p i,j = c i,j w i,jQiQj> 



Q^ is predator standing stock, 



Q^ is prey standing stock, 



W^ 4 is the selectivity factor of j for each i, and 



c± a is a rate-coefficient determined by balancing the model for steady- 

 state conditions by a method to be described. 



The material assimilated by the predator is determined by the equation 



P'i,j = p i,j A i,j. 



where A^ is a matrix of assimilation coefficients, ranging from to 1.0. 

 The assimilation coefficient is set at in cases where there is no exchange 

 between compartments. 



Unassimilated food, which is deposited in the low-nitrogen organic 

 compartment, is a function of the rate of feeding on each prey and the assimilation 

 coefficient specific to that prey: 



Fj -S(P lfj (l-A itj )). 



Respiration and harvest rates are simple functions of standing stock: 



where r^ is the respiration rate-coefficient specific to each compartment and 

 e.s is the harvesting rate-coefficient specific to each compartment. The 

 coefficient e is equivalent to the fishing mortality (F) of mathematical fishery 

 biology (Ricker 1975), which has two components, effort (f) and catchability 

 (q). 



186 



